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Systematics of the genus Floridichthys
Biochernica/SystematicsandEcology,Vol. 11, No. 3, pp. 283-294, 1963.
0305-1978/83$3.00+ 0.00 PergamonPressLtd.
Printed in Great Britain.
Systematics of the Genus Floridichthys CHARLES F. DUGGINS, JR., ALVAN A. KARLIN*, KENNETH G. RELYEAt and RALPH W: YERGER Department of Biology, Cameron University, Lawton, OK 73505, U.S.A., *Tall Timbers Research Station, Route 1, Box 160, Tallahassee FL 32312, U.S.A.; t Department of Zoology, Kuwait University, Kuwait; ~:Department of Biological Sciences, Florida State University, Tallahassee, FL 32306, U .S .A.
Key Word I n d e x - Floridichthys carpio; Floridichthys polyommus; Cyprinodontidae; starch gel electrophoresis; biochemical systematics; isozymes; biogeography. Abstract- Samples representing the three nominal subspecies of Floridichthys carpio were examined electrophoretically. Although the populations in Florida could not be distinguished completely from the populations in Yucatan by morphology, 5 of the 30 electrophoretic characters demonstrated fixed differences between Florida and Yucatan populations. Based on the observed genetic differentiation between Florida and Yucatan populations and the absence of genetic differentiation within those populations, we conclude that the Yucatan population has diverged to the species level. We, therefore, propose to elevate the nominal Yucatan subspecies Floridichthys carpio polyommus to a species status.
Introduction The genus Floridichthys (Atheriniformes; Cyprinodontidae) is considered to contain one polytypic species, Floridichthys carpio (GUnther) [1-3]. Three subspecies are currently recognized: F. c. carpio (GL~nther), peninsular Florida; F. c. polyommus Hubbs, reported only from the type locality at Champoton, Yucatan, Mexico; and F. c. barbouri Hubbs, reported only from the type locality at Progreso, Yucatan, Mexico. During field work in Yucatan we found additional populations of Floridichthys along the western, northern and eastern coasts [4]. In this study we used morphological and biochemical characters to determine the systematic relationships among the populations of Floridichthys from the Yucatan Peninsula and Florida. Results
Morphological Variation Frequency distributions for the meristic characters studied are reported in Tables 1-4 for number of dorsal fin rays, number of branched caudal fin rays, number of gill rakers and number of pectoral fin rays, respectively, of the populations studied. By inspection of the frequency distributions, it appears that the number of dorsal fin rays does not differ between Florida and Yucatan populations, (Received 5 February 1983)
but Miami area and Florida Keys populations have a lower mean and modal number. For the three other traits, modal differences are apparent between Florida and Yucatan populations, but means are not significantly different. Overlap in distributions of counts occurs for all traits, no character statistically differentiated, within one s.d., Yucatan and Florida populations, and only slight morphological divergence is suggested by the data. Analysis of variance (ANOVA) revealed that the number of dorsal fin rays and branched caudal fin rays were the best diagnostic characters (F= 4.194, 1:11 d.f., P= 0.048 and F = 92.474, 1:11 d.f., P=0.0001, respectively), even though inspection of the frequency distributions (Tables 1 and 2) show considerable overlap in ranges between Florida and Yucatan populations for these traits. The difference in dorsal fin ray number may be mainly due to low means in the Florida Keys populations. However, it is these populations that are closest geographically to Yucatan populations, perhaps rendering the data even more meaningful. Additionally, mean squares (MS) for within treatments (i.e. within Florida and Yucatan) for dorsal fin rays was small (MS = 0.110), indicating that there were no differences among samples within treatments. Therefore, even though the number of dorsal fin rays appears to be significantly different between
283
CHARLES F, DUGGINS, JR., ALVAN A. KARLIN, KENNETH G. RELYEA AND RALPH W. YERGER
284
TABLE 1. FREQUENCY DISTRIBUTION OF DORSAL FIN RAYS IN TWO SPECIES OF FLOR/DICHTHYS No. of dorsal fin rays Population
11
12
13
14
N
X
s
24 21 2 5 11 6 20 29
1
3 3 1 2
5 9 25 16 18 21 9 1
30 30 30 24 30 29 30 30
12.87 12.70 11.97 12.0~ 12.33 12.13 12.73 12.97
0.43 0.47 0.41 0.58 0.55 0.52 0.52 0.18
3 3 8 8 6
25 18 20 26 16
30 30 30 35 23
12.97 13.20 12.80 12.71 12.78
0.41 0.61 0.55 0.52 0.52
F carpio
Titusville Sebastian Inlet Miam{ Key Largo Grassy Key Big Pine Key Tampa Live Oak Island
1
F polyommus
Campeche Progreso Rio Lagartos Cancun Tulum
2 9 2 1
TABLE 2. FREQUENCY DISTRIBUTION OF BRANCHED CAUDAL FIN RAYS IN TWO SPECIES OF FLORIOICHTNYS No. of caudal fin rays Population
F carpio lqtusville Sebastian Inlet Miami Key Largo Grassy Key Big Pine Key Tampa Live Oak Island F. polyommus Campeche Progreso Rio Lagartos Cancun Tulum
15
16
17
18
19
20
N
3(
s
30 29 30 24 30 30 30 30
16.03 16.52 16.27 16.46 16.33 16.07 16.40 15.97
0.32 0.69 0.74 0.83 0.48 0.58 0.56 0.18
30 30 29 33 22
17.83 17.80 17.83 17.09 t7.68
0.65 0.76 0.93 0.95 0.65
N
X
s
29 30 30 23 30 28 30 28
11.93 11.73 12.20 t l .87 11.73 11.75 11.90 10.82
0.46 0.58 0.71 0.63 0.69 0.65 0.76 0.55
30 30 30 35 23
11.23 11.4 11.57 11.51 10.70
0.50 0.78 0.97 0.78 0.63
~. 1 3
4 1 1
1
27 17 18 17 20 20 16 29
2 3 9 2
2 9 7 4 10 6 13
9 6 4 10 3
3 2 2
17 18 19 12 17
1
4 4 1 1
2
TABLE 3. FREQUENCY DISTRIBUTION OF GILL RAKERS IN TWO SPECIES OF FLORIOICHTHYS No. of gilt rakers Population
9
F carpio Titusville Sebastian Inlet Miami Key Largo Grassy Key Big Pine Key Tampa Live Oak Island F. polyomrnus Campeche Progreso Rio Largatos Cancun Tutum
10
I
1 7
1 1 1
2 3 9
11
12
13
4 10 5 3 12 10 6 19
23 18 14 17 14 15 19 2
2 2 11 2 4 3 3
21 15 11 14 12
8 12 11 15 2
2 5 3
14
1
SYSTEMATICS OF THE GENUS FLORIDICHTHYS
285
TABLE 4. FREQUENCY DISTRIBUTION OF PECTORAL FIN RAYS IN TWO SPECIES OF FLORIDICHTHYS
No. of pectoral fin rays Population
17
18
F. carpio Titusville Sebastian Inlet Miami Key Largo Grassy Key Rig Pine Key Tampa Live Oak Island
2
4
-
1
F polyommus Campeche Progreso Rio Lagartos Cancun Tulum
-
1 6
19
20
15 24 15 12 12 17 5 23
15 5 15 6 18 6 22 6
3 2 4 7 3
18 22 17 22 18
4
Florida and Yucatan populations at the P = 0.05 level, we advise caution in interpretation and suggest that, to be rigorous and to account for the allopatric distributions involved, that the P= 0.01 level is more appropriate. The number of branched caudal fin rays does satisfy that criterion. The two remaining morphological traits, number of gill rakers and number of pectoral fin rays, could not be shown to be different between Florida and Yucatan populations (F= 1.1, 1:11 d.f., P=0.317 and F = 2.29, 1:11 d.f., P=0.158, respectively).
21
N
9 6 9 12
30 30 30 24 30 29 30 30
19.50 19.10 19.50 19.00 19.60 18.93 19.93 19.17
0,51 0.55 0.51 0.72 0.50 0.80 0.52 0.16
30 30 30 33 33
20.20 20.13 20.17 19.55 20.27
0,61 0.51 0.65 0.71 0.47
Electrophoretic Variation Of the 30 cistrons coding for proteins surveyed in this study, 10 (Gp-1,2,5, Ldh-B,C, Pep-2, M-Icdh-A, S-lcdh-A, Xdh-A and Pgm-B, see Experimental for details) were fixed for the same electromorph in all samples. Electromorph frequency variation was observed for the remaining 20 cistrons (Table 5). The variation was categorized by the degree of electromorph frequency differences among populations; i.e. type I variation was minimal and type III variation
I 2
© ~'~
GULF OF MEXICO
7
J
3
6
I0
~ 12
FIG. 1. COLLECTION LOCALITIES. Sample used for electrophoretic analysis ( • ) , morphologicalanalysis (O), both analyses ( • ) . Numbers refer
to localities of populations used for electrophoretic studies (see Experimental).
286
CHARLES F. DUGGINS, JR., ALVAN A. KARLIN, KENNETH G, RELYEA AND RALPH W. YERGER
TABLE 5. ELECTROMORPH FREQUENCIES AT 20 POLYMORPHIC CISTRONS Population" Enzyme
I
2
3
4
5
6
7
8
9
10
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.10 0.85 0.05
0.10 0.90
1.0 .
1,0
1.0 .
1.0
0.075 0.925
0.05 0.95
1.0
1.0
1.0
0.05 0.95
1.0
11
12
13
Type I variation GA-3-pdh-A
a
b Gldh
a
b c d Gp-3
-
0.325 0.675
a
b c
1.0
a
b
1.0
Gpi-B
a
-
S-Mdh-B
Pep-1
.
.
'
Gpi- A
S-Mdh-A
0.825 0.175 0.025 0.975
1.0
-
0.15 0.85
0.025
.
1.0 .
.
.
1.0 0.125 0.875
1.0 0.25 0.75
1.0 0,125 0.875
0.975 0.05 0.95
1.0 0.05 0.95
1.0 0.15 0.85
1.0 0.(]Q.5 0.975
. 0.125 0.875
. 0.15 0.80 0.05
. 0.225 0.775
. 0.30 0.70
. 0.125 0.875
. 0.25 0.75
1.0 .
1.0
1.0
1.0
1.0
1.0 .
1.0
. 0.325 0.625 0.050 1.0
1.0 .
1.0
t .0
1.0
1.0
1.0
1.0
1.0
0.975
1.0
1,0
0.925 0.075
b
1.0
c
.
a
-
b c a b c a b c
1.0
.
. 1.0
.
1.0 .
1.0
0.075 0.925 0.025 0.175 0.750 0.050 0.125 0.150 0.725
1.0
.
1,0
1.0 0.05
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.95 0.025 0.950
0.10 0.90 1.0
0.40 0.60
0.10 0.90
0.30 0.70
0.025 0.10 0.90
1.0
1.0
0.125 0.775 0.100
0.900 0.075
1.0
1.0
0.925 0.075
1.0
1.0
0.95
1.0
0.925 0.075
1.0
0.975 0.025
1.0
0.475 0.500 0.025
1.0
0.150 0.725 0.125 0.275 0.600
0.50 0.50
0.20 0.80
0.30 0.70
0.525 0.400 0.075
0.575 0.425 -
0.125
0.15 0.05 0.80
0.075 0.100 0.800
0.74 0.26
0.025 0.97
0.95
1.0
1.0
0.65 0.10 0.25
0.03
1.0
0.975 1.0
.
a
1.0
Pgm-A
b c d a b c d
1.0
1.0
0.025 0.975
a b c a b c d e f a b c d e f
0.65 0.35
0.475 0.525
0.35 0.65
0.425 0.575
0.325 0.675
0.55 0.45
0.075 0.900 0.025
0.75
0.875
0.5B
0.10
0.100
0.25
0,125
0.42
0.275 0.075 0.650
0.90
0,775 0.025 0.100
0,400 0.075 0.525
1,0
0.025
0.05
0.95 0.05
0,125 0.825 0.050 -
1.0
1.0
Pgdh-A
1.0
1,0
0.975 0.025 0.075 0.900 0.025
1.0 1,0
0.025
Type II variation Est-2
Est-3
Est-4
GA-3-pdh- C
a
0.025 0.80
1.0
1.0
0.20
0.925 0.050
0,575 0.175 0.125 0,125
0.950 0.025
0.275 0.725
1.0
1.0
0.05
0.750 0.175 0.075
0.825 0.175
0.70 0.30
0.10 0.90
0.025
0.050
b
c d
1.0 1.0
0.025
0.875 0.075
0.075 0.925
1.0
0.15 0.85
1.0
S Y S T E M A T I C S OF THE GENUS FLORIDICHTHYS
287
TABLE 5 - continued Population* Enzyme
1
2
3
4
5
6
7
8
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
9
10
11
12
13
Type III variation
Est-1
a b
G-3-pdh-B
a
0.025
b
0.975
Gp-4
c a b
Pgm-C
S-Mdh-A't Sod
c a b c
1.0
a
0.675 0.325 NP 1,0
b
-
1.0 0.975 0.025
1.0 1.0
1,0 0,95 0.05
1.0 1.0 .
-
-
1.0
t.0
1.0
1.0
1.0
0.025 1.0
0.975
1.0
1.0 .
1,0
1.0
1.0
1.0
1.0
NP 1.0
NP 1.0
NP 1.0
NP 1.0
NP 1.0
0,95 0.05 NP 1.0
1.0 1.0 .
0.725 0.275 NP 1.0
-
-
-
1.0 -
1.0 -
1.0 -
1.0
1.0
1.0 1.0 -
1.0 1.0
1.0 1.0
1.0 1.0
. 1.0 1.0 NP 1.0
NP 1.0
NP 1.0
NP 1.0
1.0 1.0
*See Fig. 1. 1"NP, Not present.
had fixed differences between populations. The location of the populations is shown in Fig. 1. Type I variation. Ten of the polymorphic cistrons
(S-Mdh-A, B, Pep-l, Pgdh-A, Pgm-A, Gpi-A, B, GA-3-pdh-A, Gldh and Gp-3) demonstrated no significant variation between populations. The same etectromorph was most frequent in all samples. For several cases, rare electromorphs (frequency less than 5%) were found in only one or a few samples. We consider these cistrons polymorphic only because, in at least one population sampled, the most common electromorph was not found in greater than 98% frequency. Type II variation. Four polymorphic cistrons (Est-2, 3, 4 and GA-3-pdh-C) demonstrated considerable interpopulation variation in electromorph frequencies. For the esterases, frequencies of the common electromorphs varied among populations. A common electromorph in one population (i.e. Est-3 ~ in population 5, Table 5) occurred in other samples at frequencies ranging from fixation (population 12) to 12.5% (populations 2 and 8). A pattern begins to emerge for GA-3-pdh-C where some Yucatan populations (9 and 10) differ from some Florida populations (6 and 7) by alternative fixed electromorphs. Type III variation. Five, or six if S-Mdh-A' is included as a special case, of the polymorphic cistrons demonstrate fixed differences between Florida and Yucatan populations. Fixed, unique
alternative electromorphs were found to differentiate Florida and Yucatan populations for Sod and Est-1 (Table 5). For three additional cistrons (Pgm-C, Gp-4 and G-3-pdh-B) the Florida and Yucatan populations did not share any of the observed electromorphs. Thus, a total of five cistrons clearly differentiated the Florida and Yucatan populations. Malate dehydrogenase was produced by only two cistrons in 12 of 13 populations of Floridichthys samples. However, in one population, Tulum, Mexico, population 13 (Table 5), an additional rapidly anodal migrating isozyme was resolved. This new isozyme, designated S-Mdh-A', is being investigated elsewhere by two of the authors (A.A.K. and C.F.D.). Discussion Hubbs [5] distinguished two presumably allopatric subspecies of Floridichthys carpio, F. c. polyommus, Champoton, and F. c. barbouri, Progreso, on the Yucatan peninsula by their coloration, size and branched caudal fin ray numbers. The electrophoretic data (Table 5) demonstrate no significant differences between topotypes of these two nominal subspecies (populations 9 and 10 for F. c. polyommus and F. c. barbouri, respectively). Similarly, no meristic character could discriminate between the nominal subspecies. Our discovery of other Yucatan populations of Floridichthys calls into question the
CHARLES F DUGGINS, JR., ALVAN A, KARLIN, KENNETHG. RELYEAAND RALPHW. YERGER
288
presumed allopatry of these nominal subspecies. From our data we conclude that only one form of Floridichthys can, to date, be demonstrated to exist in Yucatan. Relyea 131noted that two disjunct populations of Floridichthys occurred on the Florida peninsula. However, our morphological and electrophoretic data suggest that they have not differentiated. Only extreme south Florida populations, including the Florida Keys, show any differentiation, and that is for only one trait, number of dorsal fin rays. The lower counts for this trait may be expected for southernmost populations on the basis of the effects of warmer water on developmental rates. Hence, we recognize only two populations of Floridichthys, one in Florida and the other in Yucatan (Fig. 1). Although the two populations of F/oridichthys can be differentiated by only two morphological traits, and then not absolutely, they can be diagnosed by five electrophoretic characters. The Florida and Yucatan populations can be completely separated by species specific electromorphs for cistrons Est-1, Pgm-C, Gp-4, G-3-pdhB and Sod. Furthermore, electromorph frequency perturbations were observed for Est-4, an indication of potential further genetic differentiation and that the two populations are evolving independently I61. The estimates of standard genetic distance between all pairs of samples are presented in Table 6. These estimates ranged from 0.007 to 0.324 and separate the samples into two clusters, the Florida samples (1-8) and the Yucatan samples (9-13). Average genetic distances within groups were L5=0.033-+0.016 for the Florida samples and L) = 0.038 -+ 0.015 for the Yucatan samples. The
average genetic distance between groups (L~=0.281+0.027) was almost on order of magnitude greater than the within group values. This high interpopulation average genetic distance resulted from the electromorph frequencies for the five cistrons for which the groups did not share electromorphs. We note that this value (L) = 0.281) is in the range of mean genetic distance values observed among other fishes at the species level [7-101. The decision as to whether allopatric populations of a species have diverged to specific level is necessarily arbitrary. It is unknown whether upon secondary contact, should such occur in the future, disjunct populations would be capable of interbreeding, and laboratory breeding experiments cannot provide absolute answers. We suggest that the five electrophoretically detectable characters and the two morphological characters constitute a sufficient suite of characters to recognize the Yucatan population as specifically distinct from Florida populations. Although we recognize that the genetic distance values cannot be used to distinguish species [11l, we note that the observation of five differentiated cistrons is biologically significant. If we assume that our sample of 30 cistrons is an unbiased sample of the species genome [12], we can predict that the two populations are differentiated by approx. 16.7% of their total genotypes. (We acknowledge that since we are using Krebs cycle enzymes the above assumption must be tempered.) Previous investigations of another Atheriniform genus, Menidia [4, 13], demonstrated that as few as two cistrons (7.4% of the species' genotype) have been used to differentiate species. Thus, the observation of five unique fixed
TABLE 6. STANDARD GENETIC DISTANCE BETWEEN POPULATIONS OF FLORIDICHTHYS 1
2 3 4 5 6 7 8 9 10 11 12 13
0.046 0.046 0.042 0.049 0.025 0.028 0.021 0.270 0.306 0.268 0.278 0.303
2
0.014 0.024 0.042 0.064 0.057 0.054 0.258 0.287 0.320 0.326 0.298
3
0.006 0.019 0.050 0.042 0.049 0.239 0.261 0.312 0.307 0.288
4
0.007 0,02t 0.032 0.042 0.226 0.246 0.289 0.277 0.274
5
0.028 0.031 0.046 0.227 0.238 0.283 0.261 0.283
See Experimentalfor localities of numbered populations.
6
0013 0.025 0273 0.300 0273 0262 0.322
7
8
9
10
11
12
0.009 0.283 0.294 0.270 0,281 0.324
0.291 0.304 0.276 0.288 0.321
0.010 0.048 0.035 0.033
0.046 0.038 0.036
0.042 0.029
0.068
13
289
FIG. 2. PHOTOGRAPH OF FLORIDICHTHYS CARP/O (UPPER) AND F. POLYOMMUS (LOWER).
SYSTEMATICS OF THE GENUS FLORIDICHTHYS
differences and the evidence for independent lineages from esterase data for the Florida and Yucatan populations clearly demonstrate that differentiation is at least as great as differences observed among species of related fishes. Primarily on the electrophoretically detectable differentiation, and secondarily on meristic differences between Florida and Yucatan populations of Floridichthys, we propose the Yucatan population be elevated to specific rank. Of the two nominal subspecies that Hubbs {5i described from Yucatan, F. c. polyommus has page precedence. The Yucatan form is recognized as Floridichthys polyommus, and F. c. barbouri becomes a junior synonym. Floridichthys carpio (G6nther), Goldspotted Killifish (Fig. 2) Cyprinodon carpio GLinther, 1866, VI, 306 1141. Type locality: America.
Cyprinodon mydrus Goode and Bean, 1882, 433 [15]. Type locality: Pensacola, Florida. Neotype, USNM 211280, designated by Miller [16]. Floridichthys carpio Hubbs, 1926, 16 {11. Type species: Cyprinodon mydrus. Diagnosis. A species of Floridichthys distinguished from the only other member of the genus, F. polyommus, by significantly fewer branched caudal fin rays (usually 16 or 17 vs. 17 or 18 in F. polyommus, modally 16 vs. 18) and fewer dorsal fin rays (usually 12 or 13 vs. 13, modally 12 in south Florida and in the Florida Keys and 13 in peninsular Florida vs. 13 in F. polyommus). The number of gill rakers is modally 12 in F. carpio vs. 11 in F. polyornmus and the modes for pectoral fin rays are 19, occasionally 20, vs. 20. This species has an irregular series of 9-15 vertical bars on the ventral two-thirds of the sides of the body. Dorsally and caudally from the operculum there is a series of small horizontal, iridescent, oblong blotches in 3-4 rows which become fainter posteriorly (Fig. 2). The species is also distinguished by different electrophoretic mobility for Sod (a allele), Est-1 (a allele), Pgm-C (b or c allele), Gp-4 (a or b allele), and G-3-pdh-B (a or b allele). Description. In addition to the meristic features noted in the diagnosis, F. carpio has 9-11, usually 10, anal fin rays, 24-26, usually 25, vertebrae, 21-24, usually 22, lateral scales, 6-8, usually 6 or 7, predorsal scales and 15-17, usually 16, caudal peduncle circumferential scales.
291
Measurements as percent of standard length are: predorsal distance 47-57, preanal distance 64-78, body depth 30-48, head length 30-39 and caudal peduncle depth 17-24. Measurements as percent of head length are: head width 55-74, interorbital width 26-40 and eye diameter 30-44. The coloration of Floridichthys carpio varies greatly with the time of day, season, substrate, maturity, psychological condition of the fish and locality. The following description refers to an adult male from Miami, Florida. On the ventral twothirds of the side of the body there is an irregular series of 9-15 vertical bars (Fig. 2). When the fish is frightened, the bars become darker and broader. Interspersed between the bars are gold spots on an olive or cream-colored background. Dorsally and caudally from the operculum is a series of small horizontal iridescent, oblong blotches which become fainter posteriorly. Dorsal and caudal fins are spotted with melanophores. The area between the dorsal fin origin and snout is dark gray-brown. The posterior rays of the dorsal fin and anal fin are elongate. Females have smaller dorsal and anal fins and the posterior rays are not elongated. Females have less intense coloration, and have much less pigment in the dorsal and anal fins. Foster [17] also provides a useful color description. Range. Floridichthys carpio consists of two allopatric populations within the State of Florida: a west coast population that ranges from Cape San Bias in the Florida panhandle to the Florida Keys and Miami, and an east coast population from Ft. Pierce northward to Volusia County [3]. Although suitable habitat is present (personal observation), no goldspotted killifish have been reported between Ft. Pierce and Miami. Because of the lack of significant morphological and electrophoretic variation between these east coast populations and Florida Keys populations, we question whether this small distributional gap is real, but it also occurs in other killifishes [3]. Tabb and Manning [181 reported that Floridichthys carpio was rare in extreme southwest Florida. Extreme southwest and/or southeast Florida is also a region of disjunction in the ranges of Fundulus similis, F. grandis, L ucania parva and Menidia peninsulae [3, 13]. Lack of collecting in southwest Florida may be reflected (Fig. 1). At the periphery of its range, the occurrence of F. carpio is sporadic, especially on the Florida west coast from Tampa northward. A collection from
292
CHARLES F, DUGGINS, JR., ALVAN A, KARLIN, KENNETH G. RELYEA AND RALPH W. YERGER
the Pensacola area was noted by Goode and Bean [15), and another from Carrabelle by Fowler [19l under the name Cyprinodon rnydrus. No subsequent collections have been reported from these areas. We have collected goldspotted killifish at Live Oak Island (Wakulla County, Florida) and one of us (K.G.R.) and Kilby [201 have collected the species at Cedar Key. It should be noted that Garman [21], G~nter [22], Carr and Goin [231 and Rosen [241 have reported F. carpio from Texas. These records are no doubt based on Cyprinodon sp. and represent repetition of an error in the literature. Information on the ecology, ethology and embryology of F. carpio may be found in Foster [17] and Kaill [25]. Descriptions of cephalic sensory canals and skull morphology are also available [26, 271. Habitat. Floridichthys carpio inhabits protected beaches or estuaries characterized by clear water and a sand, marl or calcareous substrate. It is usually found in salinities greater than 25 parts per thousand.
side of the body beginning on a level with the dorsal rim of the operculum and extending ventrally to the belly, and a series of oblong metallic brown blotches extending dorsally and posteriorly to the caudal fin (Fig. 2). This species is also distinguished by different electrophoretic mobilities for Sod (b allelle) Est-1 (b allele), Pgm-C (a allele), Gp-4 (c allele) and G-3-pdh-B (c allele). Description. In addition to the meristic characters given in the diagnosis, F. polyommus has 8-11, usually 10, anal fin rays, 24-26, usually 25, vertebrae, 21-23, usually 22, lateral scales, 58, usually 6-7, predorsal scales and 16, rarely 15, caudal peduncle circumferential scales. Measurements as percent of standard length are: predorsal distance 50-59, preanal distance 66-78, body depth 33-47, head length 30-37, head width 19-26 and caudal peduncle depth 18-25. Measurements as percent of head length are: head width 61-73, interorbital width 26-39 and eye diameter 31-43. The fish observed in this study were collected in March 1978 and March 1979. The largest F. polyommus collected was 64 mm SL; most specimens were between 40 and 60 mm SL. As in Ftoridichthys polyommus Hubbs, Ocellated F. carpio, the coloration of F. polyommus is Killifish (Fig. 2) variable. We did not observe the striking blue Floridichthys carpio polyommus Hubbs, 1936 [51. which surrounded the iridescent spots on the Type locality: Champoton, Campeche, Yucatan, sides of the body described by Hubbs [5] on Mexico. Holotype: male, 64 mm SL. Catalog No. specimens collected in August. A variable number, 102186 Museum of Zoology, University of usually 4-8, of narrow, dark vertical bars are Michigan. present on the side of the body; the bars begin on a Floridichthys carpio barbouri Hubbs, 1936 [5l. level with the dorsal rim of the opercular opening Type locality: Cienaga, 2 km southwest of and continue ventrally to the belly. Between these Progreso, Yucatan, Holotype: male, 90 mm SL. bars are gold spots on a silver or cream-colored Catalog No. 102167 Museum of Zoology, background. From the edge of the operculum a University of Michigan. series of oblong, metallic brown blotches extend Diagnosis. A species of Floridichthys distin- dorsally and posteriorly to the caudal fin. The guished from the only other species of the genus, blotches decrease in size posteriorly. On the cheek F. carpio, by significantly higher number of and opercle there are horizontal to oblique golden branched caudal fin rays (17 or 18, usually 18 vs. 16 bars. The body and fins show yellow-gold or 17, usually 16; modally 18 and 16, respectively) coloration which varies in intensity. The caudal fin and the higher number of dorsal fin rays (12 or 13, is fringed in gold and contains approximately five usually and modally 13 vs. modally 12 in Florida vertical rows of golden spots. The dorsal fin is Keys populations of F. carpio and 13 in peninsular yellow with interspersed melanophores. The Florida populations). Gill rakers are modally 11 in pectoral and pelvic fins are washed with a weak this species and modally 12 in all F. carpio popula- yellow color. The anal fin is fringed in gold with tions except in the northern Gulf of Mexico. The rows of vertical yellow-gold spots. Both the dorsal number of pectoral fin rays is modally 20 in F. and anal fins increase greatly in length in mature polyommus, and usually 19, occasionally 20, in F. males. For additional information see ref. [5]. carpio. There are 4 - 8 narrow, vertical bars on the Range. Floridichthyspolyommus was collected
293
SYSTEMATICS OF THE GENUS FLORIDICHTHYS in Y u c a t a n a t t h e localities s h o w n in Fig. 1. W e s u s p e c t t h a t Floridichthys p o l y o m m u s is c o n t i n u ously distributed along the coast of the Yucatan p e n i n s u l a w h e r e v e r t h e r e is s u i t a b l e h a b i t a t . Habitat. Field o b s e r v a t i o n s i n d i c a t e t h a t t h e h a b i t a t o f F. p o l y o m m u s is similar t o t h a t o f F. carpio. Floridichthys p o l y o m m u s is g e n e r a l l y f o u n d in w a t e r w i t h salinities g r e a t e r t h a n 25 p a r t s per t h o u s a n d , b u t in this s t u d y o n e c o l l e c t i o n w a s m a d e in a f r e s h w a t e r lake 2 5 . 5 k m s o u t h o f T u l u m , Y u c a t a n , w h e r e t h e salinity w a s 1 p a r t per thousand.
Experimental Between June 1977 and December 1977 collections were made at 16 localities (see below and Fig. 1). Field collecting methods were described previously 14, 101. Localities (see Fig. 1). Florida, U.S.A.: (1) Brevard Co., Titusville (20 specimens for electrophoresis; 30 specimens for morphological analysis); (2) Brevard Co., Sebastian Inlet (20, 30); (3) Dade Co., Miami (20, 30); (4) Monroe Co., Key Largo (20, 24); (5) Monroe Co., Lower Matecumbe Key (20, 0); (6) Monroe Co., Big Pine Key (20, 29); (7) Collier Co,, Everglades City (20, 0); (8) Pinellas Co., Crystal Beach (20, 0), Yucatan, Mexico: (9) Campeche, Champoton (type locality for F. c. polyommus, 20, 30); (10) Yucatan, Progreso (type locality for F. c. barbouri, 20, 30); (11) Yucatan, Rio Lagartos (20, 30); (12) Quintana Roo, Cancun (20, 35); (13) Quintana Roo, Tulum (20, 23). Additional populations from Florida were examined morphologically but not used for electrophoresis: Hillsborough Co., Tampa Bay (30); Dade Co., Miami (30); Wakulla Co., Live Oak Island (30); Monroe Co., Grassy Key (29); Monroe Co., Big Pine Key (30); Brevard Co., Titusville (30). All measurements (made with dial calipers and recorded to the nearest 0.1 mm) and counts were taken from the left side. Although many measurements and counts were recorded, as described by Hubbs and Lagler 1281, only four were of interest; the remaining were either non-variant or too variable to be of systematic value. The characters were number of dorsal fin rays, number of branched caudal fin rays, number of all gill rakers and number of pectoral fin rays. One-way analysis of variance was performed on the meristic data with the aid of Statistical Programs for the Social Sciences (SPSS) available from the Florida State University Computer Center. Techniques of horizontal starch gel electrophoresis were similar to those described by Brewer (291, Selander et aL f301 and Duggins et aL (10]. The cistron nomenclature system follows Duggins et aL fl01. When electromorph (allele) variation occurred, the electromorph with greatest anodal migration was called a, the next b, and so on. The 30 cistrons coding for proteins in this study were: general proteins (Gp-1, 2, 3, 4, 5); esterases (Est-1, 2, 3, 4); 1-1eucyl-l-tyrosine peptidase (Pep-l, 2) superoxide dismutase (Sod); glucosephosphate isomerases (Gpi-A, B); lactate dehydrogenases (Ldh-B,C); glyceraldehyde-3-
phosphate dehydrogenases (GA-3-pdh-A, C); isocitrate dehydrogenases (M-Icdh-A, S-lcdh-A); glucose dehydrogenase (Gldh); malate dehydrogenases (NAD dependent) (S-Mdh-A, B, A'); phosphogluconate dehydrogenase (Pgdh-A); phosphoglucomutases (Pgm-A, B, C); =r-glycerophosphate dehydrogenase (G-3-pdh-B); and xanthine dehydrogenase (Xdh-A). To summarize electromorph variation, Nei's 1121 standard genetic distance estimate, D, was calculated from electromorph frequencies. A standard genetic distance matrix was constructed from all pairwise comparisons. When appropriate, arithmetic means (average genetic distances) were calculated from the standard genetic distance matrix.
Acknowledgements-We thank Dr. Robert R. Miller for valuable suggestions and assistance in obtaining permits to collect fish in Mexico, and Drs. J. C. Avise, D. G. Buth, C. R. Gilbert, C. R. Robins and L. Rivas for their assistance. Sandi Gilchrist was helpful with statistical analyses. We are grateful to the following for field assistance: R. Cowdery, W. Giesy, S. Harding, D. and E. Leslie, C. Mesing and G. Relyea. Special appreciation is due C. Teaf for many hours of field assistance. We thank the Fish and Wildlife Commissions of Texas and Mexico for their co-operation in providing collecting permits. This study was supported in part by a Grant-in-aid of Research from Sigma Xi, and a grant from the Smithsonian Institution L. P. Schultz Fund. Portions of this work were submitted by C, F. Duggins, Jr. to the Florida State University Department of Biological Sciences in partial fulfilment of the requirements for the Ph.D. degree in Biology. References 1. Hubbs, C. L. (1926) Misc. PubL Mus. ZooL Univ. Mich.
13,1. 2. Miller, R. R. (1956) Occas. Pap. Mus. ZooL Univ, Mich. 581, 1.
3. Relyea, K. G. (1975)Sci. BioL J. 1,49. 4. Duggins, C. F., Jr. (1980) Doctoral Dissertation, Florida State University. 5. Hubbs, C. L. (1936) Carnegie Inst Washington Publ. 457, 157. 6. Futuyma, D. J. and G. C. Mayer (1980) Syst. ZooL 29, 254. 7. Arise, J. C. (1974) Syst. Zoo/. 23,465. 8. Arise, J. C~, J. J. Smith and F. J. Ayala (1975) Evolution 29,411. 9. Avise, J. C. and F. J. Ayala (1976) Evolution30,46. 10. Duggins, C. F,, Jr., Kadin, A. A. and Relyea, K. G. (1983) Copeia 564. 11. Turner, B. J. (1973) Evolution28,281. 12. Nei, M. (1972)Am. Nat. 106, 283. 13, Johnson, M. S. (1975) Copeia662. 14, GUnther, A. (1866) Catalog of Fishes of the British Museum Vl, 306. 15. Goode, G. B, and T. H. Bean (1882) Proc. U,S. Nat. Mus. 5, 412. 16 Miller, R, R. (1974)Copeia981. 17. Foster, N. R. (1967) Doctoral Dissertation, Cornell University.
294
CHARLES F DUGGINS, JR, ALVANA KARLIN, KENNETH G. RELYEAANDRALPHW. YERGER
18. Tabb, D. C. and R. B. Manning (1961) Bull. Mar. Sci. Gulf Caribb. 11,552. 19. Fowler, H. (1917) Copeia 43, 38. 20. Kilby, J. D. (1955) TulaneStud. ZooL Bot. 2, 175. 21. Garman, S. (1895) Mere. Mus. Comp. Zool. 19, 1. 22. GLinter, G. ( 1941 ) Ecology 22, 202. 23. Carr, A. and Goin, C. J. (1969) Guide to the Reptiles, Amphibians and Freshwater Fishes of Florida. 341 pp. Univ. Florida Press, Gainesville. 24. Rosen, D. E. (1973)Mem. Sears Found. Mar. Res. 1,229.
25. Kaill, W. M. (1967) Doctoral Dissertation, Cornell Univer sity. 26. Gosline, W. A. (1949) Occas. Pap. Mus. Zool. Univ. Mich. 591, 1. 27. Starkes, E. C. (1904) Biol. Bull. 7,254. 28. Hubbs, C. L. and Lagler, K. F. (1958) Cranbrook Inst. Sci. Bull. 457, 157. 29. Brewer, G. J. (1970) An Introduction to Isozyme Techniques. 263 pp. Academic Press, New York. 30. Selander, R. K,, Smith, M. H., Yang, S. Y., Johnson, W. E. and Gentry, J. B. (1971) Univ. Tex. Bull. 7103, 49.
0305-1978/83$3.00+ 0.00 PergamonPressLtd.
Printed in Great Britain.
Systematics of the Genus Floridichthys CHARLES F. DUGGINS, JR., ALVAN A. KARLIN*, KENNETH G. RELYEAt and RALPH W: YERGER Department of Biology, Cameron University, Lawton, OK 73505, U.S.A., *Tall Timbers Research Station, Route 1, Box 160, Tallahassee FL 32312, U.S.A.; t Department of Zoology, Kuwait University, Kuwait; ~:Department of Biological Sciences, Florida State University, Tallahassee, FL 32306, U .S .A.
Key Word I n d e x - Floridichthys carpio; Floridichthys polyommus; Cyprinodontidae; starch gel electrophoresis; biochemical systematics; isozymes; biogeography. Abstract- Samples representing the three nominal subspecies of Floridichthys carpio were examined electrophoretically. Although the populations in Florida could not be distinguished completely from the populations in Yucatan by morphology, 5 of the 30 electrophoretic characters demonstrated fixed differences between Florida and Yucatan populations. Based on the observed genetic differentiation between Florida and Yucatan populations and the absence of genetic differentiation within those populations, we conclude that the Yucatan population has diverged to the species level. We, therefore, propose to elevate the nominal Yucatan subspecies Floridichthys carpio polyommus to a species status.
Introduction The genus Floridichthys (Atheriniformes; Cyprinodontidae) is considered to contain one polytypic species, Floridichthys carpio (GUnther) [1-3]. Three subspecies are currently recognized: F. c. carpio (GL~nther), peninsular Florida; F. c. polyommus Hubbs, reported only from the type locality at Champoton, Yucatan, Mexico; and F. c. barbouri Hubbs, reported only from the type locality at Progreso, Yucatan, Mexico. During field work in Yucatan we found additional populations of Floridichthys along the western, northern and eastern coasts [4]. In this study we used morphological and biochemical characters to determine the systematic relationships among the populations of Floridichthys from the Yucatan Peninsula and Florida. Results
Morphological Variation Frequency distributions for the meristic characters studied are reported in Tables 1-4 for number of dorsal fin rays, number of branched caudal fin rays, number of gill rakers and number of pectoral fin rays, respectively, of the populations studied. By inspection of the frequency distributions, it appears that the number of dorsal fin rays does not differ between Florida and Yucatan populations, (Received 5 February 1983)
but Miami area and Florida Keys populations have a lower mean and modal number. For the three other traits, modal differences are apparent between Florida and Yucatan populations, but means are not significantly different. Overlap in distributions of counts occurs for all traits, no character statistically differentiated, within one s.d., Yucatan and Florida populations, and only slight morphological divergence is suggested by the data. Analysis of variance (ANOVA) revealed that the number of dorsal fin rays and branched caudal fin rays were the best diagnostic characters (F= 4.194, 1:11 d.f., P= 0.048 and F = 92.474, 1:11 d.f., P=0.0001, respectively), even though inspection of the frequency distributions (Tables 1 and 2) show considerable overlap in ranges between Florida and Yucatan populations for these traits. The difference in dorsal fin ray number may be mainly due to low means in the Florida Keys populations. However, it is these populations that are closest geographically to Yucatan populations, perhaps rendering the data even more meaningful. Additionally, mean squares (MS) for within treatments (i.e. within Florida and Yucatan) for dorsal fin rays was small (MS = 0.110), indicating that there were no differences among samples within treatments. Therefore, even though the number of dorsal fin rays appears to be significantly different between
283
CHARLES F, DUGGINS, JR., ALVAN A. KARLIN, KENNETH G. RELYEA AND RALPH W. YERGER
284
TABLE 1. FREQUENCY DISTRIBUTION OF DORSAL FIN RAYS IN TWO SPECIES OF FLOR/DICHTHYS No. of dorsal fin rays Population
11
12
13
14
N
X
s
24 21 2 5 11 6 20 29
1
3 3 1 2
5 9 25 16 18 21 9 1
30 30 30 24 30 29 30 30
12.87 12.70 11.97 12.0~ 12.33 12.13 12.73 12.97
0.43 0.47 0.41 0.58 0.55 0.52 0.52 0.18
3 3 8 8 6
25 18 20 26 16
30 30 30 35 23
12.97 13.20 12.80 12.71 12.78
0.41 0.61 0.55 0.52 0.52
F carpio
Titusville Sebastian Inlet Miam{ Key Largo Grassy Key Big Pine Key Tampa Live Oak Island
1
F polyommus
Campeche Progreso Rio Lagartos Cancun Tulum
2 9 2 1
TABLE 2. FREQUENCY DISTRIBUTION OF BRANCHED CAUDAL FIN RAYS IN TWO SPECIES OF FLORIOICHTNYS No. of caudal fin rays Population
F carpio lqtusville Sebastian Inlet Miami Key Largo Grassy Key Big Pine Key Tampa Live Oak Island F. polyommus Campeche Progreso Rio Lagartos Cancun Tulum
15
16
17
18
19
20
N
3(
s
30 29 30 24 30 30 30 30
16.03 16.52 16.27 16.46 16.33 16.07 16.40 15.97
0.32 0.69 0.74 0.83 0.48 0.58 0.56 0.18
30 30 29 33 22
17.83 17.80 17.83 17.09 t7.68
0.65 0.76 0.93 0.95 0.65
N
X
s
29 30 30 23 30 28 30 28
11.93 11.73 12.20 t l .87 11.73 11.75 11.90 10.82
0.46 0.58 0.71 0.63 0.69 0.65 0.76 0.55
30 30 30 35 23
11.23 11.4 11.57 11.51 10.70
0.50 0.78 0.97 0.78 0.63
~. 1 3
4 1 1
1
27 17 18 17 20 20 16 29
2 3 9 2
2 9 7 4 10 6 13
9 6 4 10 3
3 2 2
17 18 19 12 17
1
4 4 1 1
2
TABLE 3. FREQUENCY DISTRIBUTION OF GILL RAKERS IN TWO SPECIES OF FLORIOICHTHYS No. of gilt rakers Population
9
F carpio Titusville Sebastian Inlet Miami Key Largo Grassy Key Big Pine Key Tampa Live Oak Island F. polyomrnus Campeche Progreso Rio Largatos Cancun Tutum
10
I
1 7
1 1 1
2 3 9
11
12
13
4 10 5 3 12 10 6 19
23 18 14 17 14 15 19 2
2 2 11 2 4 3 3
21 15 11 14 12
8 12 11 15 2
2 5 3
14
1
SYSTEMATICS OF THE GENUS FLORIDICHTHYS
285
TABLE 4. FREQUENCY DISTRIBUTION OF PECTORAL FIN RAYS IN TWO SPECIES OF FLORIDICHTHYS
No. of pectoral fin rays Population
17
18
F. carpio Titusville Sebastian Inlet Miami Key Largo Grassy Key Rig Pine Key Tampa Live Oak Island
2
4
-
1
F polyommus Campeche Progreso Rio Lagartos Cancun Tulum
-
1 6
19
20
15 24 15 12 12 17 5 23
15 5 15 6 18 6 22 6
3 2 4 7 3
18 22 17 22 18
4
Florida and Yucatan populations at the P = 0.05 level, we advise caution in interpretation and suggest that, to be rigorous and to account for the allopatric distributions involved, that the P= 0.01 level is more appropriate. The number of branched caudal fin rays does satisfy that criterion. The two remaining morphological traits, number of gill rakers and number of pectoral fin rays, could not be shown to be different between Florida and Yucatan populations (F= 1.1, 1:11 d.f., P=0.317 and F = 2.29, 1:11 d.f., P=0.158, respectively).
21
N
9 6 9 12
30 30 30 24 30 29 30 30
19.50 19.10 19.50 19.00 19.60 18.93 19.93 19.17
0,51 0.55 0.51 0.72 0.50 0.80 0.52 0.16
30 30 30 33 33
20.20 20.13 20.17 19.55 20.27
0,61 0.51 0.65 0.71 0.47
Electrophoretic Variation Of the 30 cistrons coding for proteins surveyed in this study, 10 (Gp-1,2,5, Ldh-B,C, Pep-2, M-Icdh-A, S-lcdh-A, Xdh-A and Pgm-B, see Experimental for details) were fixed for the same electromorph in all samples. Electromorph frequency variation was observed for the remaining 20 cistrons (Table 5). The variation was categorized by the degree of electromorph frequency differences among populations; i.e. type I variation was minimal and type III variation
I 2
© ~'~
GULF OF MEXICO
7
J
3
6
I0
~ 12
FIG. 1. COLLECTION LOCALITIES. Sample used for electrophoretic analysis ( • ) , morphologicalanalysis (O), both analyses ( • ) . Numbers refer
to localities of populations used for electrophoretic studies (see Experimental).
286
CHARLES F. DUGGINS, JR., ALVAN A. KARLIN, KENNETH G, RELYEA AND RALPH W. YERGER
TABLE 5. ELECTROMORPH FREQUENCIES AT 20 POLYMORPHIC CISTRONS Population" Enzyme
I
2
3
4
5
6
7
8
9
10
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.10 0.85 0.05
0.10 0.90
1.0 .
1,0
1.0 .
1.0
0.075 0.925
0.05 0.95
1.0
1.0
1.0
0.05 0.95
1.0
11
12
13
Type I variation GA-3-pdh-A
a
b Gldh
a
b c d Gp-3
-
0.325 0.675
a
b c
1.0
a
b
1.0
Gpi-B
a
-
S-Mdh-B
Pep-1
.
.
'
Gpi- A
S-Mdh-A
0.825 0.175 0.025 0.975
1.0
-
0.15 0.85
0.025
.
1.0 .
.
.
1.0 0.125 0.875
1.0 0.25 0.75
1.0 0,125 0.875
0.975 0.05 0.95
1.0 0.05 0.95
1.0 0.15 0.85
1.0 0.(]Q.5 0.975
. 0.125 0.875
. 0.15 0.80 0.05
. 0.225 0.775
. 0.30 0.70
. 0.125 0.875
. 0.25 0.75
1.0 .
1.0
1.0
1.0
1.0
1.0 .
1.0
. 0.325 0.625 0.050 1.0
1.0 .
1.0
t .0
1.0
1.0
1.0
1.0
1.0
0.975
1.0
1,0
0.925 0.075
b
1.0
c
.
a
-
b c a b c a b c
1.0
.
. 1.0
.
1.0 .
1.0
0.075 0.925 0.025 0.175 0.750 0.050 0.125 0.150 0.725
1.0
.
1,0
1.0 0.05
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.95 0.025 0.950
0.10 0.90 1.0
0.40 0.60
0.10 0.90
0.30 0.70
0.025 0.10 0.90
1.0
1.0
0.125 0.775 0.100
0.900 0.075
1.0
1.0
0.925 0.075
1.0
1.0
0.95
1.0
0.925 0.075
1.0
0.975 0.025
1.0
0.475 0.500 0.025
1.0
0.150 0.725 0.125 0.275 0.600
0.50 0.50
0.20 0.80
0.30 0.70
0.525 0.400 0.075
0.575 0.425 -
0.125
0.15 0.05 0.80
0.075 0.100 0.800
0.74 0.26
0.025 0.97
0.95
1.0
1.0
0.65 0.10 0.25
0.03
1.0
0.975 1.0
.
a
1.0
Pgm-A
b c d a b c d
1.0
1.0
0.025 0.975
a b c a b c d e f a b c d e f
0.65 0.35
0.475 0.525
0.35 0.65
0.425 0.575
0.325 0.675
0.55 0.45
0.075 0.900 0.025
0.75
0.875
0.5B
0.10
0.100
0.25
0,125
0.42
0.275 0.075 0.650
0.90
0,775 0.025 0.100
0,400 0.075 0.525
1,0
0.025
0.05
0.95 0.05
0,125 0.825 0.050 -
1.0
1.0
Pgdh-A
1.0
1,0
0.975 0.025 0.075 0.900 0.025
1.0 1,0
0.025
Type II variation Est-2
Est-3
Est-4
GA-3-pdh- C
a
0.025 0.80
1.0
1.0
0.20
0.925 0.050
0,575 0.175 0.125 0,125
0.950 0.025
0.275 0.725
1.0
1.0
0.05
0.750 0.175 0.075
0.825 0.175
0.70 0.30
0.10 0.90
0.025
0.050
b
c d
1.0 1.0
0.025
0.875 0.075
0.075 0.925
1.0
0.15 0.85
1.0
S Y S T E M A T I C S OF THE GENUS FLORIDICHTHYS
287
TABLE 5 - continued Population* Enzyme
1
2
3
4
5
6
7
8
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
9
10
11
12
13
Type III variation
Est-1
a b
G-3-pdh-B
a
0.025
b
0.975
Gp-4
c a b
Pgm-C
S-Mdh-A't Sod
c a b c
1.0
a
0.675 0.325 NP 1,0
b
-
1.0 0.975 0.025
1.0 1.0
1,0 0,95 0.05
1.0 1.0 .
-
-
1.0
t.0
1.0
1.0
1.0
0.025 1.0
0.975
1.0
1.0 .
1,0
1.0
1.0
1.0
1.0
NP 1.0
NP 1.0
NP 1.0
NP 1.0
NP 1.0
0,95 0.05 NP 1.0
1.0 1.0 .
0.725 0.275 NP 1.0
-
-
-
1.0 -
1.0 -
1.0 -
1.0
1.0
1.0 1.0 -
1.0 1.0
1.0 1.0
1.0 1.0
. 1.0 1.0 NP 1.0
NP 1.0
NP 1.0
NP 1.0
1.0 1.0
*See Fig. 1. 1"NP, Not present.
had fixed differences between populations. The location of the populations is shown in Fig. 1. Type I variation. Ten of the polymorphic cistrons
(S-Mdh-A, B, Pep-l, Pgdh-A, Pgm-A, Gpi-A, B, GA-3-pdh-A, Gldh and Gp-3) demonstrated no significant variation between populations. The same etectromorph was most frequent in all samples. For several cases, rare electromorphs (frequency less than 5%) were found in only one or a few samples. We consider these cistrons polymorphic only because, in at least one population sampled, the most common electromorph was not found in greater than 98% frequency. Type II variation. Four polymorphic cistrons (Est-2, 3, 4 and GA-3-pdh-C) demonstrated considerable interpopulation variation in electromorph frequencies. For the esterases, frequencies of the common electromorphs varied among populations. A common electromorph in one population (i.e. Est-3 ~ in population 5, Table 5) occurred in other samples at frequencies ranging from fixation (population 12) to 12.5% (populations 2 and 8). A pattern begins to emerge for GA-3-pdh-C where some Yucatan populations (9 and 10) differ from some Florida populations (6 and 7) by alternative fixed electromorphs. Type III variation. Five, or six if S-Mdh-A' is included as a special case, of the polymorphic cistrons demonstrate fixed differences between Florida and Yucatan populations. Fixed, unique
alternative electromorphs were found to differentiate Florida and Yucatan populations for Sod and Est-1 (Table 5). For three additional cistrons (Pgm-C, Gp-4 and G-3-pdh-B) the Florida and Yucatan populations did not share any of the observed electromorphs. Thus, a total of five cistrons clearly differentiated the Florida and Yucatan populations. Malate dehydrogenase was produced by only two cistrons in 12 of 13 populations of Floridichthys samples. However, in one population, Tulum, Mexico, population 13 (Table 5), an additional rapidly anodal migrating isozyme was resolved. This new isozyme, designated S-Mdh-A', is being investigated elsewhere by two of the authors (A.A.K. and C.F.D.). Discussion Hubbs [5] distinguished two presumably allopatric subspecies of Floridichthys carpio, F. c. polyommus, Champoton, and F. c. barbouri, Progreso, on the Yucatan peninsula by their coloration, size and branched caudal fin ray numbers. The electrophoretic data (Table 5) demonstrate no significant differences between topotypes of these two nominal subspecies (populations 9 and 10 for F. c. polyommus and F. c. barbouri, respectively). Similarly, no meristic character could discriminate between the nominal subspecies. Our discovery of other Yucatan populations of Floridichthys calls into question the
CHARLES F DUGGINS, JR., ALVAN A, KARLIN, KENNETHG. RELYEAAND RALPHW. YERGER
288
presumed allopatry of these nominal subspecies. From our data we conclude that only one form of Floridichthys can, to date, be demonstrated to exist in Yucatan. Relyea 131noted that two disjunct populations of Floridichthys occurred on the Florida peninsula. However, our morphological and electrophoretic data suggest that they have not differentiated. Only extreme south Florida populations, including the Florida Keys, show any differentiation, and that is for only one trait, number of dorsal fin rays. The lower counts for this trait may be expected for southernmost populations on the basis of the effects of warmer water on developmental rates. Hence, we recognize only two populations of Floridichthys, one in Florida and the other in Yucatan (Fig. 1). Although the two populations of F/oridichthys can be differentiated by only two morphological traits, and then not absolutely, they can be diagnosed by five electrophoretic characters. The Florida and Yucatan populations can be completely separated by species specific electromorphs for cistrons Est-1, Pgm-C, Gp-4, G-3-pdhB and Sod. Furthermore, electromorph frequency perturbations were observed for Est-4, an indication of potential further genetic differentiation and that the two populations are evolving independently I61. The estimates of standard genetic distance between all pairs of samples are presented in Table 6. These estimates ranged from 0.007 to 0.324 and separate the samples into two clusters, the Florida samples (1-8) and the Yucatan samples (9-13). Average genetic distances within groups were L5=0.033-+0.016 for the Florida samples and L) = 0.038 -+ 0.015 for the Yucatan samples. The
average genetic distance between groups (L~=0.281+0.027) was almost on order of magnitude greater than the within group values. This high interpopulation average genetic distance resulted from the electromorph frequencies for the five cistrons for which the groups did not share electromorphs. We note that this value (L) = 0.281) is in the range of mean genetic distance values observed among other fishes at the species level [7-101. The decision as to whether allopatric populations of a species have diverged to specific level is necessarily arbitrary. It is unknown whether upon secondary contact, should such occur in the future, disjunct populations would be capable of interbreeding, and laboratory breeding experiments cannot provide absolute answers. We suggest that the five electrophoretically detectable characters and the two morphological characters constitute a sufficient suite of characters to recognize the Yucatan population as specifically distinct from Florida populations. Although we recognize that the genetic distance values cannot be used to distinguish species [11l, we note that the observation of five differentiated cistrons is biologically significant. If we assume that our sample of 30 cistrons is an unbiased sample of the species genome [12], we can predict that the two populations are differentiated by approx. 16.7% of their total genotypes. (We acknowledge that since we are using Krebs cycle enzymes the above assumption must be tempered.) Previous investigations of another Atheriniform genus, Menidia [4, 13], demonstrated that as few as two cistrons (7.4% of the species' genotype) have been used to differentiate species. Thus, the observation of five unique fixed
TABLE 6. STANDARD GENETIC DISTANCE BETWEEN POPULATIONS OF FLORIDICHTHYS 1
2 3 4 5 6 7 8 9 10 11 12 13
0.046 0.046 0.042 0.049 0.025 0.028 0.021 0.270 0.306 0.268 0.278 0.303
2
0.014 0.024 0.042 0.064 0.057 0.054 0.258 0.287 0.320 0.326 0.298
3
0.006 0.019 0.050 0.042 0.049 0.239 0.261 0.312 0.307 0.288
4
0.007 0,02t 0.032 0.042 0.226 0.246 0.289 0.277 0.274
5
0.028 0.031 0.046 0.227 0.238 0.283 0.261 0.283
See Experimentalfor localities of numbered populations.
6
0013 0.025 0273 0.300 0273 0262 0.322
7
8
9
10
11
12
0.009 0.283 0.294 0.270 0,281 0.324
0.291 0.304 0.276 0.288 0.321
0.010 0.048 0.035 0.033
0.046 0.038 0.036
0.042 0.029
0.068
13
289
FIG. 2. PHOTOGRAPH OF FLORIDICHTHYS CARP/O (UPPER) AND F. POLYOMMUS (LOWER).
SYSTEMATICS OF THE GENUS FLORIDICHTHYS
differences and the evidence for independent lineages from esterase data for the Florida and Yucatan populations clearly demonstrate that differentiation is at least as great as differences observed among species of related fishes. Primarily on the electrophoretically detectable differentiation, and secondarily on meristic differences between Florida and Yucatan populations of Floridichthys, we propose the Yucatan population be elevated to specific rank. Of the two nominal subspecies that Hubbs {5i described from Yucatan, F. c. polyommus has page precedence. The Yucatan form is recognized as Floridichthys polyommus, and F. c. barbouri becomes a junior synonym. Floridichthys carpio (G6nther), Goldspotted Killifish (Fig. 2) Cyprinodon carpio GLinther, 1866, VI, 306 1141. Type locality: America.
Cyprinodon mydrus Goode and Bean, 1882, 433 [15]. Type locality: Pensacola, Florida. Neotype, USNM 211280, designated by Miller [16]. Floridichthys carpio Hubbs, 1926, 16 {11. Type species: Cyprinodon mydrus. Diagnosis. A species of Floridichthys distinguished from the only other member of the genus, F. polyommus, by significantly fewer branched caudal fin rays (usually 16 or 17 vs. 17 or 18 in F. polyommus, modally 16 vs. 18) and fewer dorsal fin rays (usually 12 or 13 vs. 13, modally 12 in south Florida and in the Florida Keys and 13 in peninsular Florida vs. 13 in F. polyommus). The number of gill rakers is modally 12 in F. carpio vs. 11 in F. polyornmus and the modes for pectoral fin rays are 19, occasionally 20, vs. 20. This species has an irregular series of 9-15 vertical bars on the ventral two-thirds of the sides of the body. Dorsally and caudally from the operculum there is a series of small horizontal, iridescent, oblong blotches in 3-4 rows which become fainter posteriorly (Fig. 2). The species is also distinguished by different electrophoretic mobility for Sod (a allele), Est-1 (a allele), Pgm-C (b or c allele), Gp-4 (a or b allele), and G-3-pdh-B (a or b allele). Description. In addition to the meristic features noted in the diagnosis, F. carpio has 9-11, usually 10, anal fin rays, 24-26, usually 25, vertebrae, 21-24, usually 22, lateral scales, 6-8, usually 6 or 7, predorsal scales and 15-17, usually 16, caudal peduncle circumferential scales.
291
Measurements as percent of standard length are: predorsal distance 47-57, preanal distance 64-78, body depth 30-48, head length 30-39 and caudal peduncle depth 17-24. Measurements as percent of head length are: head width 55-74, interorbital width 26-40 and eye diameter 30-44. The coloration of Floridichthys carpio varies greatly with the time of day, season, substrate, maturity, psychological condition of the fish and locality. The following description refers to an adult male from Miami, Florida. On the ventral twothirds of the side of the body there is an irregular series of 9-15 vertical bars (Fig. 2). When the fish is frightened, the bars become darker and broader. Interspersed between the bars are gold spots on an olive or cream-colored background. Dorsally and caudally from the operculum is a series of small horizontal iridescent, oblong blotches which become fainter posteriorly. Dorsal and caudal fins are spotted with melanophores. The area between the dorsal fin origin and snout is dark gray-brown. The posterior rays of the dorsal fin and anal fin are elongate. Females have smaller dorsal and anal fins and the posterior rays are not elongated. Females have less intense coloration, and have much less pigment in the dorsal and anal fins. Foster [17] also provides a useful color description. Range. Floridichthys carpio consists of two allopatric populations within the State of Florida: a west coast population that ranges from Cape San Bias in the Florida panhandle to the Florida Keys and Miami, and an east coast population from Ft. Pierce northward to Volusia County [3]. Although suitable habitat is present (personal observation), no goldspotted killifish have been reported between Ft. Pierce and Miami. Because of the lack of significant morphological and electrophoretic variation between these east coast populations and Florida Keys populations, we question whether this small distributional gap is real, but it also occurs in other killifishes [3]. Tabb and Manning [181 reported that Floridichthys carpio was rare in extreme southwest Florida. Extreme southwest and/or southeast Florida is also a region of disjunction in the ranges of Fundulus similis, F. grandis, L ucania parva and Menidia peninsulae [3, 13]. Lack of collecting in southwest Florida may be reflected (Fig. 1). At the periphery of its range, the occurrence of F. carpio is sporadic, especially on the Florida west coast from Tampa northward. A collection from
292
CHARLES F, DUGGINS, JR., ALVAN A, KARLIN, KENNETH G. RELYEA AND RALPH W. YERGER
the Pensacola area was noted by Goode and Bean [15), and another from Carrabelle by Fowler [19l under the name Cyprinodon rnydrus. No subsequent collections have been reported from these areas. We have collected goldspotted killifish at Live Oak Island (Wakulla County, Florida) and one of us (K.G.R.) and Kilby [201 have collected the species at Cedar Key. It should be noted that Garman [21], G~nter [22], Carr and Goin [231 and Rosen [241 have reported F. carpio from Texas. These records are no doubt based on Cyprinodon sp. and represent repetition of an error in the literature. Information on the ecology, ethology and embryology of F. carpio may be found in Foster [17] and Kaill [25]. Descriptions of cephalic sensory canals and skull morphology are also available [26, 271. Habitat. Floridichthys carpio inhabits protected beaches or estuaries characterized by clear water and a sand, marl or calcareous substrate. It is usually found in salinities greater than 25 parts per thousand.
side of the body beginning on a level with the dorsal rim of the operculum and extending ventrally to the belly, and a series of oblong metallic brown blotches extending dorsally and posteriorly to the caudal fin (Fig. 2). This species is also distinguished by different electrophoretic mobilities for Sod (b allelle) Est-1 (b allele), Pgm-C (a allele), Gp-4 (c allele) and G-3-pdh-B (c allele). Description. In addition to the meristic characters given in the diagnosis, F. polyommus has 8-11, usually 10, anal fin rays, 24-26, usually 25, vertebrae, 21-23, usually 22, lateral scales, 58, usually 6-7, predorsal scales and 16, rarely 15, caudal peduncle circumferential scales. Measurements as percent of standard length are: predorsal distance 50-59, preanal distance 66-78, body depth 33-47, head length 30-37, head width 19-26 and caudal peduncle depth 18-25. Measurements as percent of head length are: head width 61-73, interorbital width 26-39 and eye diameter 31-43. The fish observed in this study were collected in March 1978 and March 1979. The largest F. polyommus collected was 64 mm SL; most specimens were between 40 and 60 mm SL. As in Ftoridichthys polyommus Hubbs, Ocellated F. carpio, the coloration of F. polyommus is Killifish (Fig. 2) variable. We did not observe the striking blue Floridichthys carpio polyommus Hubbs, 1936 [51. which surrounded the iridescent spots on the Type locality: Champoton, Campeche, Yucatan, sides of the body described by Hubbs [5] on Mexico. Holotype: male, 64 mm SL. Catalog No. specimens collected in August. A variable number, 102186 Museum of Zoology, University of usually 4-8, of narrow, dark vertical bars are Michigan. present on the side of the body; the bars begin on a Floridichthys carpio barbouri Hubbs, 1936 [5l. level with the dorsal rim of the opercular opening Type locality: Cienaga, 2 km southwest of and continue ventrally to the belly. Between these Progreso, Yucatan, Holotype: male, 90 mm SL. bars are gold spots on a silver or cream-colored Catalog No. 102167 Museum of Zoology, background. From the edge of the operculum a University of Michigan. series of oblong, metallic brown blotches extend Diagnosis. A species of Floridichthys distin- dorsally and posteriorly to the caudal fin. The guished from the only other species of the genus, blotches decrease in size posteriorly. On the cheek F. carpio, by significantly higher number of and opercle there are horizontal to oblique golden branched caudal fin rays (17 or 18, usually 18 vs. 16 bars. The body and fins show yellow-gold or 17, usually 16; modally 18 and 16, respectively) coloration which varies in intensity. The caudal fin and the higher number of dorsal fin rays (12 or 13, is fringed in gold and contains approximately five usually and modally 13 vs. modally 12 in Florida vertical rows of golden spots. The dorsal fin is Keys populations of F. carpio and 13 in peninsular yellow with interspersed melanophores. The Florida populations). Gill rakers are modally 11 in pectoral and pelvic fins are washed with a weak this species and modally 12 in all F. carpio popula- yellow color. The anal fin is fringed in gold with tions except in the northern Gulf of Mexico. The rows of vertical yellow-gold spots. Both the dorsal number of pectoral fin rays is modally 20 in F. and anal fins increase greatly in length in mature polyommus, and usually 19, occasionally 20, in F. males. For additional information see ref. [5]. carpio. There are 4 - 8 narrow, vertical bars on the Range. Floridichthyspolyommus was collected
293
SYSTEMATICS OF THE GENUS FLORIDICHTHYS in Y u c a t a n a t t h e localities s h o w n in Fig. 1. W e s u s p e c t t h a t Floridichthys p o l y o m m u s is c o n t i n u ously distributed along the coast of the Yucatan p e n i n s u l a w h e r e v e r t h e r e is s u i t a b l e h a b i t a t . Habitat. Field o b s e r v a t i o n s i n d i c a t e t h a t t h e h a b i t a t o f F. p o l y o m m u s is similar t o t h a t o f F. carpio. Floridichthys p o l y o m m u s is g e n e r a l l y f o u n d in w a t e r w i t h salinities g r e a t e r t h a n 25 p a r t s per t h o u s a n d , b u t in this s t u d y o n e c o l l e c t i o n w a s m a d e in a f r e s h w a t e r lake 2 5 . 5 k m s o u t h o f T u l u m , Y u c a t a n , w h e r e t h e salinity w a s 1 p a r t per thousand.
Experimental Between June 1977 and December 1977 collections were made at 16 localities (see below and Fig. 1). Field collecting methods were described previously 14, 101. Localities (see Fig. 1). Florida, U.S.A.: (1) Brevard Co., Titusville (20 specimens for electrophoresis; 30 specimens for morphological analysis); (2) Brevard Co., Sebastian Inlet (20, 30); (3) Dade Co., Miami (20, 30); (4) Monroe Co., Key Largo (20, 24); (5) Monroe Co., Lower Matecumbe Key (20, 0); (6) Monroe Co., Big Pine Key (20, 29); (7) Collier Co,, Everglades City (20, 0); (8) Pinellas Co., Crystal Beach (20, 0), Yucatan, Mexico: (9) Campeche, Champoton (type locality for F. c. polyommus, 20, 30); (10) Yucatan, Progreso (type locality for F. c. barbouri, 20, 30); (11) Yucatan, Rio Lagartos (20, 30); (12) Quintana Roo, Cancun (20, 35); (13) Quintana Roo, Tulum (20, 23). Additional populations from Florida were examined morphologically but not used for electrophoresis: Hillsborough Co., Tampa Bay (30); Dade Co., Miami (30); Wakulla Co., Live Oak Island (30); Monroe Co., Grassy Key (29); Monroe Co., Big Pine Key (30); Brevard Co., Titusville (30). All measurements (made with dial calipers and recorded to the nearest 0.1 mm) and counts were taken from the left side. Although many measurements and counts were recorded, as described by Hubbs and Lagler 1281, only four were of interest; the remaining were either non-variant or too variable to be of systematic value. The characters were number of dorsal fin rays, number of branched caudal fin rays, number of all gill rakers and number of pectoral fin rays. One-way analysis of variance was performed on the meristic data with the aid of Statistical Programs for the Social Sciences (SPSS) available from the Florida State University Computer Center. Techniques of horizontal starch gel electrophoresis were similar to those described by Brewer (291, Selander et aL f301 and Duggins et aL (10]. The cistron nomenclature system follows Duggins et aL fl01. When electromorph (allele) variation occurred, the electromorph with greatest anodal migration was called a, the next b, and so on. The 30 cistrons coding for proteins in this study were: general proteins (Gp-1, 2, 3, 4, 5); esterases (Est-1, 2, 3, 4); 1-1eucyl-l-tyrosine peptidase (Pep-l, 2) superoxide dismutase (Sod); glucosephosphate isomerases (Gpi-A, B); lactate dehydrogenases (Ldh-B,C); glyceraldehyde-3-
phosphate dehydrogenases (GA-3-pdh-A, C); isocitrate dehydrogenases (M-Icdh-A, S-lcdh-A); glucose dehydrogenase (Gldh); malate dehydrogenases (NAD dependent) (S-Mdh-A, B, A'); phosphogluconate dehydrogenase (Pgdh-A); phosphoglucomutases (Pgm-A, B, C); =r-glycerophosphate dehydrogenase (G-3-pdh-B); and xanthine dehydrogenase (Xdh-A). To summarize electromorph variation, Nei's 1121 standard genetic distance estimate, D, was calculated from electromorph frequencies. A standard genetic distance matrix was constructed from all pairwise comparisons. When appropriate, arithmetic means (average genetic distances) were calculated from the standard genetic distance matrix.
Acknowledgements-We thank Dr. Robert R. Miller for valuable suggestions and assistance in obtaining permits to collect fish in Mexico, and Drs. J. C. Avise, D. G. Buth, C. R. Gilbert, C. R. Robins and L. Rivas for their assistance. Sandi Gilchrist was helpful with statistical analyses. We are grateful to the following for field assistance: R. Cowdery, W. Giesy, S. Harding, D. and E. Leslie, C. Mesing and G. Relyea. Special appreciation is due C. Teaf for many hours of field assistance. We thank the Fish and Wildlife Commissions of Texas and Mexico for their co-operation in providing collecting permits. This study was supported in part by a Grant-in-aid of Research from Sigma Xi, and a grant from the Smithsonian Institution L. P. Schultz Fund. Portions of this work were submitted by C, F. Duggins, Jr. to the Florida State University Department of Biological Sciences in partial fulfilment of the requirements for the Ph.D. degree in Biology. References 1. Hubbs, C. L. (1926) Misc. PubL Mus. ZooL Univ. Mich.
13,1. 2. Miller, R. R. (1956) Occas. Pap. Mus. ZooL Univ, Mich. 581, 1.
3. Relyea, K. G. (1975)Sci. BioL J. 1,49. 4. Duggins, C. F., Jr. (1980) Doctoral Dissertation, Florida State University. 5. Hubbs, C. L. (1936) Carnegie Inst Washington Publ. 457, 157. 6. Futuyma, D. J. and G. C. Mayer (1980) Syst. ZooL 29, 254. 7. Arise, J. C. (1974) Syst. Zoo/. 23,465. 8. Arise, J. C~, J. J. Smith and F. J. Ayala (1975) Evolution 29,411. 9. Avise, J. C. and F. J. Ayala (1976) Evolution30,46. 10. Duggins, C. F,, Jr., Kadin, A. A. and Relyea, K. G. (1983) Copeia 564. 11. Turner, B. J. (1973) Evolution28,281. 12. Nei, M. (1972)Am. Nat. 106, 283. 13, Johnson, M. S. (1975) Copeia662. 14, GUnther, A. (1866) Catalog of Fishes of the British Museum Vl, 306. 15. Goode, G. B, and T. H. Bean (1882) Proc. U,S. Nat. Mus. 5, 412. 16 Miller, R, R. (1974)Copeia981. 17. Foster, N. R. (1967) Doctoral Dissertation, Cornell University.
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18. Tabb, D. C. and R. B. Manning (1961) Bull. Mar. Sci. Gulf Caribb. 11,552. 19. Fowler, H. (1917) Copeia 43, 38. 20. Kilby, J. D. (1955) TulaneStud. ZooL Bot. 2, 175. 21. Garman, S. (1895) Mere. Mus. Comp. Zool. 19, 1. 22. GLinter, G. ( 1941 ) Ecology 22, 202. 23. Carr, A. and Goin, C. J. (1969) Guide to the Reptiles, Amphibians and Freshwater Fishes of Florida. 341 pp. Univ. Florida Press, Gainesville. 24. Rosen, D. E. (1973)Mem. Sears Found. Mar. Res. 1,229.
25. Kaill, W. M. (1967) Doctoral Dissertation, Cornell Univer sity. 26. Gosline, W. A. (1949) Occas. Pap. Mus. Zool. Univ. Mich. 591, 1. 27. Starkes, E. C. (1904) Biol. Bull. 7,254. 28. Hubbs, C. L. and Lagler, K. F. (1958) Cranbrook Inst. Sci. Bull. 457, 157. 29. Brewer, G. J. (1970) An Introduction to Isozyme Techniques. 263 pp. Academic Press, New York. 30. Selander, R. K,, Smith, M. H., Yang, S. Y., Johnson, W. E. and Gentry, J. B. (1971) Univ. Tex. Bull. 7103, 49.