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Species interrelationships and evolution in the pliocene endemic faunas of apricena (Gargano Peninsula-Italy)
SPECIES INTERRELATIONSHIPS ENDEMIC
FAUNAS
AND EVOLUTION
OF APRICENA
(GARGANO
IN THE PLIOCENE
PENINSULA
- ITALY)
by CLAUDIO DE GIULI * & DANILO TORRE *
SUMMARY
R.~SUMI~
Preliminary observations allow to advance hypotheses on evolutive strategies of three coexisting species of the murid Microtia in Pliocene fissure fillings of the Gargano Peninsula.
Quelques observations pr61iminaires permettent d'avancer des hypotheses sur les strat6gies ~volutives de trois esl~ces coexistantes du murid6 Microtia dans les remplissages karstiques de la Presqu'~le du Gargano.
KEY WORDS : INSULAR FAUNAS, EVOLUTION, NEOGENE, ITALY. MOTS-CLI~S : FAUNES INSULAIRES, I~VOLUTION, NI~OGI~NE, ITALIE.
* Dipartimento di Scienze della Terra - Universit/L di Firenze, via La Pira, 4, 50121 Firenze, Italia.
Geobios, M6m. sp6cial n ~ 8
p. 379-383, I fig.
Lyon, 1984
- - 380 - -
1. The development of studies on some faunas from the Gargano Peninsula (Foggia-ltaly) pointed out some interesting characters concerning relationships among different taxa and their evolution. Particularly interesting was the association of different species, all of one murid genus. It was possible to recognize dynamic equilibria among at least three species of endemic murids and a species of Prolagus in a relatively short time span. In this preliminary work we used only the most general elements emerging from our own research and from Freudenthal, 1976.
2. Several karst fissures, found during the quarry works widespread in the surroundings of the villages of Apricena and Poggio Imperiale, yielded two types of faunas. Biharian-late Villafranchian faunas occur in fissures and large sinkholes filled with a gray sandy silt (De Giuli & Torre, in press). Older faunas occur in fissures filled with ~ terra rossa >~ (Freudenthal, 1971). The most characteristic element of these faunas is an endemic murid Microtia whose evolutionary trend allowed Freudenthal, 1976, to dress a chronologic order to the various fissures. According to Freudenthal, 1973, and following works the faunal association is : Insectivora :
Deinogalerix, several species of this giant galericine have been described by Freudenthal, 1972, and Butler, 1980. Galericine, a species of normal size. Soricine, a species, poorly represented. Rodentia : Gliridae, two species, one of large size, the second o f normal size. We believe that the small species could be referred to aff. Peridyromys while the large one is a Glis. Circetidae, two species one similar to Kowalskia the other one of larger size. Younger fissures lack Cricetidae. Muridae, Apodemus occurs in all fissures. Microtia is present with several forms of different size and of different evolutionary degree which can be grouped into at least three lineages. Lagomorpha :
Prolagus is a common species. In a fissure we found a single specimen of a Leporid.
Carnivora : A large otterlike mustelid is poorly represented. Artiodactyla : Several species of a dwarf cervid, Oplitomeryx are described by Leinders (in press - personal communication). Ayes : Ballmann, 1973 & 1976 described a rich bird fauna among which Strigiformes and Falconiformes that show size increase along several evolutionary lineages. Amphibians and Reptiles also occur but no better reference is available. We have found one single specimen of a large Varanoidea. The analysis of the fauna with various endemic features and different compositions suggests not only insularity for the area under study but also for nearby areas. We face evidence of an archipelago and this is in accordance with the known caenozoic history of the carbonate platform of the Apulian province.
3. The purpose of this note does not require full taxonomic statements but some elements need to be pointed out. Clear continuous lineages can be identified as chronospecies and therefore caution is necessary in splitting specific names. There are difficulties in using some of the specific names already defined.
Prolagus shows apomorphic characters close to P. michauxi but some plesiomorphies, as small size of the premolar foramen and the completeness of enamel in upper P2 and P3, suggest an independent origin from forerunners belonging to the P. oenigensis group.
Apodemus, as we already pointed out (De Giuli & Torre, in press) can be referred to Apodemus ex gr. occitanus. 4. Freudenthal, 1971, referred the fissures to a Vallesian or Turolian age. Our evidence is for a younger age of the fissure fillings. This age is pointed out by the occurrence since the oldest fissures of Apodemus ex gr. occitanus. This murid could not migrate to
--
Gargano earlier than the upper part of the G. punticuiata biozone according to the affinity with the form found at Cascina Arondelli, a local fauna included in the Triversa Faunal Unit (Azzaroli & alii, 1982). To the same conclusion leads a study of marine sequences bordering the area (G. Valleri, personal communication). Moreover a Pliocene age is strengthened by the occurrence of the Leporid.
Apodemus and the Leporid testify a last immigration event from the mainland and superpose themselves to an endemic association resulting from at least two older immigration events. A first one is suggested by Deinogalerix, Oplitomeryx and Peridyromys, whose ancestors must have migrated around the Lower-Middle Miocene. The forerunners of Prolagus and of Microtia (Occitanomys or Stephanomys) had to migrate in the Uppermost Miocene. The studies on marine sequences furthermore suggest that no fissure filling can be younger than the occtirrence of G. inflata in the Adriatic Sea (G. Vallesi, personal communication). Time span for the documented faunas is therefore of about a million years at most. In terms of standard marine biostratigraphy it can not exceed the interval between the uppermost N 19 and the lower N 21 biozones.
Freudenthal, 1976, observed in a lineage of Microtia, supposed to be documented in all fissures, a continuous increase of size and morphological complexity in M t and M 3. He dressed a chronological sequence of the fissure fillings on the basis of the size. Even if differences are not relevant we prefere to order the fissures according to morphologic evolution. We used only M ~ features and the method of quantifying morphology is the one of Freudenthal, 1976. We will refer to it as morphological evolutionary level, MEL.
5. In the faunal association a subsystem is detectable, composed by the different species of Microtia, the Prolagus and their predators Strigiformes and Falco9niformes. Microtia and Prolagus are the specialized forms that characterize the open environments of the area. Interactions among these forms were such as to determine changements, as extinctions or as development of various evolutive strategies. The general trend in the subsystem, with a few exceptions, is size increase.
381
--
Present knowledge allows us to divide fissures in two groups (fig. 1). A younger one where three lineages of Microtia are generally present and an older one where only one lineage can be detected. The boundary between the two groups can be placed between P8183/D and Chirb 27 fissures. In the older fissures sporadic occurrences of Microtia not referrable to the main lineage according to the size, provide evidence of unsuccessful immigrations. Also, in the lower part of the younger succession there are some miscellaneous forms intermediate in size between the main lineages, that may represent groups not tolerated by the system. Our present goal is to give tentative explanations to the different evolutive strategies of the three Microtia lineages occurring in the younger fissures. According to Freudenthal, 1976, lineages are quoted as n. 1, the smallest size group, as n. 2, the medium size group and as n. 3 largest size one. The earliest evolutive step of Microtia is not documented. The ancestor was possibly related to Occitanomys or Stephanomys, thus already with a tendency to occupy the adaptative zone which will be later typical of voles. Competition under insular conditions is sufficient to explain increase of size. Increase of morphological complexity namely the number of crests and hypsodonty shows a refinement of adaptation made possible by the lack of more specialized competitors, as Mimomys was on the mainland. MEL 5 seems to be a sufficient adaptation to the environment. Actually lineages 1 and 3 do not show any further advance and lineage 2 reaches this level at the boundary between younger and older fissure groups. At the base of younger fissures, Chirb 27 yielded specimens belonging to all the three lineages with the same MEL 5 but differences in size are sharp. We believe, as Freudenthal, 1976, that members of lineage 2 represent the evolution of the indigenous stock while those referred to lineages 1 and 3 are immigrants. The differences in size of these immigrants could be related to the extent of the originating islands. The evolutionary strategies followed by the lineages have been different. Lineage 1 shows only a poor size decrease, lineage 3 only size increase, while lineage 2 shows increase in size and in MEL. Each lineage will be discussed separately.
--
382
--
LINEAGE 1
LINEAGE 3
LINEAGE 2 Pr~
03 LU rr
1
,/,i./ /, , /~,,~
1 1 P77:2
/ /
6
03 03 i
ll
//
/
t/
9
.............
. MEL
, ............
I
................... _ MEL
I
55
rw LU
/
O Z
i m
/
i
B
)
=C27
.~
<
PSI-
830
/"
/
9 )
/
O
9
// (/
03
~
i m
LU re-
/
i p77/4
03 _ MEL
03 1
4.5 _
Freudenthal's
our
LL
samples
samples
LU 9
-O
MEL
Microtia
miscellaneous
0
3
4
5
6
7
8
I
I
I
J
1
i
6
8
10
1=2
I
I
1
Microtia
Prolagus
Fig. 1 -
,.,.I
4
tooth
row
M1
length
length
Variation of the mean length of Microtia Mt in time. The relative chronology of the fissure fillings is inferred by the evolutional increase of the number of M1 crests ( = MEL). The fissure fillings sequence, from the oldest to the youngest, is : Variations chronologiques de la longueur moyenne de la M] de Microtia. La chxonologie relative des remplissages karstiques est inf~r~ par l~ ~volutive du nombre des cretes de Ml ( = MEL). La s~quencr des remplissages, du plus ancien au plus r~cent, est : Biancone, Rinascita 1, Trefossi 1, Cantatore 3 A, Fina D, P 77/4, Chirb 7 A, Nazario bivio, P 77/5, Nazario 4, P 81-83/D, Monte Granata, Pizzicoli 4, Chir6 27, Chir6 5 A, ChirO 9, Chirb 6, C 80/1, Chir6 14 A, P 80/1, P 77/3, Posticchia 1 B, P 77/2, Gervasio 1, Plrro 11 A, Chirb 25, Chirb 24, SG 83/2, San Giovannino, Gervasio 2.
- - 383
Lineage 1 Populations of this lineage seem to be the most stable, means of M 1 length range f r o m 3.69 to 4.13 while the M E L randomly ranges from 4.87 fo 5.20. Slight size reduction occurs in the uppermost fissures. A possible explanation of this size reduction could be an increasing mortality equally interesting young and adult individuals, so that precorious reproduction would be favoured. Rise of undifferentiated mortability can be related to an increase of selective pressure external to the population. We can exclude strong food deficiency in the environment, at least in earlier times, according to the good survival condition of the largest Microtia and Prolagus. Therefore selective pressure must be linked to interspecific are really more efficient competitors while the small size of the members of the lineage males them easy preys in any stage of their development.
Lineage 3 Populations of this lineage increase from mean M J length from 7.55 to 8.36 while M E L randomly ranges between 4.94 and 5.13. Rise of intraspecific competition is sufficient to explain the increase of size. Intraspecific competition tends to inorease infant probability of death favouring a selection of individuals with larger size and a faster body development. External factors could also be invoked but strongly focused interactions must be envisaged.
Lineage 2 This is the lineage that is believed to be indigenous and to be present in all fissures. We think that there are not sufficient reasons in Freudenthal, 1976, to place the smallest form, Microtia parva of the Biancone fissure, at the base of the lineage. Derivation f r o m the largest one, Microtia maiuscola, is equally possible. Mean of M 9 length ranges from 3.15 to 6.75 in the whole sequence, in the younger fissure group it starts from 5.59. M E L reaches the mean value of 6.4. Along this lineage there is not only size increase but also a continuous morphological evolution in M t and M3. Other than in lineage 3 the evolutionary strategy o f lineage 2 must be explained with more complex interrelationships. Along this lineage size increase alone was not a sufficient reward. Evidently increase of chewing efficiency was also needed. Really morphological evolution can not be charged to internal factors as sister lineages stop at M E L 5. Also intraspecific competition does not seem enough. An active external competitors must be envisaged in Prolagus. 6. It is evident that these hypotheses need to be verified and refined with more analysis and field work. It is clear in any case that the Gargano is a wonderful natural l a b o r a t o r y for studying p h e n o m e n a of microevolution and of ecological interrelationships among different species. Also effects of the changing areal extent can be probably tested.
REFERENCES
AZZAROLI A., DE GIUL1 C., FICCARELLI G. & TORRE D. (1982) - Table of the stratigraphic distribution of terrestrial mammalian faunas in Italy from the Pliocene to the early middle Pleistocene. Geogr. Fis. Dinam. Quat., 5, 55-58.
DE GIULI C. & TORRE D. (1983) - A microfauna with Allophaiomys pliocaenicus from Gargano (Southern Italy). Palaeont. It. (in press).
BALLMANN P. (1973) - Fossile VOgel aus deg Neogen der Halbinsel Gargano (Italien). Scripta GeoL, 17, 1-75.
FREUDENTHAL M. (1972) - Deinogalerix koenigswald, nov. gen., nov. sp., a giant insectivore from the Neogene of Italy. Scripta GeoL, 14, 1-19.
BALLMANN P. (1976) - Fossile VOgel aus dem Neogen der Halbinsel Gargano (Italien), zweiter Teil. Scripta Geol., 38, 1-59.
FREUDENTHAL M. (1973) - Ein Riesenigel aus dem Neogen Italiens. Natur u. Museum., 103, 427-430.
BUTLER P.M. (1981) - The giant erinaceid insectivore, Deinogalerix FREUDENTHAL, from the Upper Miocene of Gargano, Italy. Scripta Geol, 57 (1980), 1-72.
FREUDENTHAL M. (1971) - Neogene vertebrates from the Gargano Peninsula, Italy. Scripta Geol., 3, 1-10.
FREUDENTHAL M. (1976) - Rodent stratigraphy of some Miocene fissure fillings in Gargano (prov. Fog#a, Italy). Scripta Geol., 37, 1-23.
FAUNAS
AND EVOLUTION
OF APRICENA
(GARGANO
IN THE PLIOCENE
PENINSULA
- ITALY)
by CLAUDIO DE GIULI * & DANILO TORRE *
SUMMARY
R.~SUMI~
Preliminary observations allow to advance hypotheses on evolutive strategies of three coexisting species of the murid Microtia in Pliocene fissure fillings of the Gargano Peninsula.
Quelques observations pr61iminaires permettent d'avancer des hypotheses sur les strat6gies ~volutives de trois esl~ces coexistantes du murid6 Microtia dans les remplissages karstiques de la Presqu'~le du Gargano.
KEY WORDS : INSULAR FAUNAS, EVOLUTION, NEOGENE, ITALY. MOTS-CLI~S : FAUNES INSULAIRES, I~VOLUTION, NI~OGI~NE, ITALIE.
* Dipartimento di Scienze della Terra - Universit/L di Firenze, via La Pira, 4, 50121 Firenze, Italia.
Geobios, M6m. sp6cial n ~ 8
p. 379-383, I fig.
Lyon, 1984
- - 380 - -
1. The development of studies on some faunas from the Gargano Peninsula (Foggia-ltaly) pointed out some interesting characters concerning relationships among different taxa and their evolution. Particularly interesting was the association of different species, all of one murid genus. It was possible to recognize dynamic equilibria among at least three species of endemic murids and a species of Prolagus in a relatively short time span. In this preliminary work we used only the most general elements emerging from our own research and from Freudenthal, 1976.
2. Several karst fissures, found during the quarry works widespread in the surroundings of the villages of Apricena and Poggio Imperiale, yielded two types of faunas. Biharian-late Villafranchian faunas occur in fissures and large sinkholes filled with a gray sandy silt (De Giuli & Torre, in press). Older faunas occur in fissures filled with ~ terra rossa >~ (Freudenthal, 1971). The most characteristic element of these faunas is an endemic murid Microtia whose evolutionary trend allowed Freudenthal, 1976, to dress a chronologic order to the various fissures. According to Freudenthal, 1973, and following works the faunal association is : Insectivora :
Deinogalerix, several species of this giant galericine have been described by Freudenthal, 1972, and Butler, 1980. Galericine, a species of normal size. Soricine, a species, poorly represented. Rodentia : Gliridae, two species, one of large size, the second o f normal size. We believe that the small species could be referred to aff. Peridyromys while the large one is a Glis. Circetidae, two species one similar to Kowalskia the other one of larger size. Younger fissures lack Cricetidae. Muridae, Apodemus occurs in all fissures. Microtia is present with several forms of different size and of different evolutionary degree which can be grouped into at least three lineages. Lagomorpha :
Prolagus is a common species. In a fissure we found a single specimen of a Leporid.
Carnivora : A large otterlike mustelid is poorly represented. Artiodactyla : Several species of a dwarf cervid, Oplitomeryx are described by Leinders (in press - personal communication). Ayes : Ballmann, 1973 & 1976 described a rich bird fauna among which Strigiformes and Falconiformes that show size increase along several evolutionary lineages. Amphibians and Reptiles also occur but no better reference is available. We have found one single specimen of a large Varanoidea. The analysis of the fauna with various endemic features and different compositions suggests not only insularity for the area under study but also for nearby areas. We face evidence of an archipelago and this is in accordance with the known caenozoic history of the carbonate platform of the Apulian province.
3. The purpose of this note does not require full taxonomic statements but some elements need to be pointed out. Clear continuous lineages can be identified as chronospecies and therefore caution is necessary in splitting specific names. There are difficulties in using some of the specific names already defined.
Prolagus shows apomorphic characters close to P. michauxi but some plesiomorphies, as small size of the premolar foramen and the completeness of enamel in upper P2 and P3, suggest an independent origin from forerunners belonging to the P. oenigensis group.
Apodemus, as we already pointed out (De Giuli & Torre, in press) can be referred to Apodemus ex gr. occitanus. 4. Freudenthal, 1971, referred the fissures to a Vallesian or Turolian age. Our evidence is for a younger age of the fissure fillings. This age is pointed out by the occurrence since the oldest fissures of Apodemus ex gr. occitanus. This murid could not migrate to
--
Gargano earlier than the upper part of the G. punticuiata biozone according to the affinity with the form found at Cascina Arondelli, a local fauna included in the Triversa Faunal Unit (Azzaroli & alii, 1982). To the same conclusion leads a study of marine sequences bordering the area (G. Valleri, personal communication). Moreover a Pliocene age is strengthened by the occurrence of the Leporid.
Apodemus and the Leporid testify a last immigration event from the mainland and superpose themselves to an endemic association resulting from at least two older immigration events. A first one is suggested by Deinogalerix, Oplitomeryx and Peridyromys, whose ancestors must have migrated around the Lower-Middle Miocene. The forerunners of Prolagus and of Microtia (Occitanomys or Stephanomys) had to migrate in the Uppermost Miocene. The studies on marine sequences furthermore suggest that no fissure filling can be younger than the occtirrence of G. inflata in the Adriatic Sea (G. Vallesi, personal communication). Time span for the documented faunas is therefore of about a million years at most. In terms of standard marine biostratigraphy it can not exceed the interval between the uppermost N 19 and the lower N 21 biozones.
Freudenthal, 1976, observed in a lineage of Microtia, supposed to be documented in all fissures, a continuous increase of size and morphological complexity in M t and M 3. He dressed a chronological sequence of the fissure fillings on the basis of the size. Even if differences are not relevant we prefere to order the fissures according to morphologic evolution. We used only M ~ features and the method of quantifying morphology is the one of Freudenthal, 1976. We will refer to it as morphological evolutionary level, MEL.
5. In the faunal association a subsystem is detectable, composed by the different species of Microtia, the Prolagus and their predators Strigiformes and Falco9niformes. Microtia and Prolagus are the specialized forms that characterize the open environments of the area. Interactions among these forms were such as to determine changements, as extinctions or as development of various evolutive strategies. The general trend in the subsystem, with a few exceptions, is size increase.
381
--
Present knowledge allows us to divide fissures in two groups (fig. 1). A younger one where three lineages of Microtia are generally present and an older one where only one lineage can be detected. The boundary between the two groups can be placed between P8183/D and Chirb 27 fissures. In the older fissures sporadic occurrences of Microtia not referrable to the main lineage according to the size, provide evidence of unsuccessful immigrations. Also, in the lower part of the younger succession there are some miscellaneous forms intermediate in size between the main lineages, that may represent groups not tolerated by the system. Our present goal is to give tentative explanations to the different evolutive strategies of the three Microtia lineages occurring in the younger fissures. According to Freudenthal, 1976, lineages are quoted as n. 1, the smallest size group, as n. 2, the medium size group and as n. 3 largest size one. The earliest evolutive step of Microtia is not documented. The ancestor was possibly related to Occitanomys or Stephanomys, thus already with a tendency to occupy the adaptative zone which will be later typical of voles. Competition under insular conditions is sufficient to explain increase of size. Increase of morphological complexity namely the number of crests and hypsodonty shows a refinement of adaptation made possible by the lack of more specialized competitors, as Mimomys was on the mainland. MEL 5 seems to be a sufficient adaptation to the environment. Actually lineages 1 and 3 do not show any further advance and lineage 2 reaches this level at the boundary between younger and older fissure groups. At the base of younger fissures, Chirb 27 yielded specimens belonging to all the three lineages with the same MEL 5 but differences in size are sharp. We believe, as Freudenthal, 1976, that members of lineage 2 represent the evolution of the indigenous stock while those referred to lineages 1 and 3 are immigrants. The differences in size of these immigrants could be related to the extent of the originating islands. The evolutionary strategies followed by the lineages have been different. Lineage 1 shows only a poor size decrease, lineage 3 only size increase, while lineage 2 shows increase in size and in MEL. Each lineage will be discussed separately.
--
382
--
LINEAGE 1
LINEAGE 3
LINEAGE 2 Pr~
03 LU rr
1
,/,i./ /, , /~,,~
1 1 P77:2
/ /
6
03 03 i
ll
//
/
t/
9
.............
. MEL
, ............
I
................... _ MEL
I
55
rw LU
/
O Z
i m
/
i
B
)
=C27
.~
<
PSI-
830
/"
/
9 )
/
O
9
// (/
03
~
i m
LU re-
/
i p77/4
03 _ MEL
03 1
4.5 _
Freudenthal's
our
LL
samples
samples
LU 9
-O
MEL
Microtia
miscellaneous
0
3
4
5
6
7
8
I
I
I
J
1
i
6
8
10
1=2
I
I
1
Microtia
Prolagus
Fig. 1 -
,.,.I
4
tooth
row
M1
length
length
Variation of the mean length of Microtia Mt in time. The relative chronology of the fissure fillings is inferred by the evolutional increase of the number of M1 crests ( = MEL). The fissure fillings sequence, from the oldest to the youngest, is : Variations chronologiques de la longueur moyenne de la M] de Microtia. La chxonologie relative des remplissages karstiques est inf~r~ par l~ ~volutive du nombre des cretes de Ml ( = MEL). La s~quencr des remplissages, du plus ancien au plus r~cent, est : Biancone, Rinascita 1, Trefossi 1, Cantatore 3 A, Fina D, P 77/4, Chirb 7 A, Nazario bivio, P 77/5, Nazario 4, P 81-83/D, Monte Granata, Pizzicoli 4, Chir6 27, Chir6 5 A, ChirO 9, Chirb 6, C 80/1, Chir6 14 A, P 80/1, P 77/3, Posticchia 1 B, P 77/2, Gervasio 1, Plrro 11 A, Chirb 25, Chirb 24, SG 83/2, San Giovannino, Gervasio 2.
- - 383
Lineage 1 Populations of this lineage seem to be the most stable, means of M 1 length range f r o m 3.69 to 4.13 while the M E L randomly ranges from 4.87 fo 5.20. Slight size reduction occurs in the uppermost fissures. A possible explanation of this size reduction could be an increasing mortality equally interesting young and adult individuals, so that precorious reproduction would be favoured. Rise of undifferentiated mortability can be related to an increase of selective pressure external to the population. We can exclude strong food deficiency in the environment, at least in earlier times, according to the good survival condition of the largest Microtia and Prolagus. Therefore selective pressure must be linked to interspecific are really more efficient competitors while the small size of the members of the lineage males them easy preys in any stage of their development.
Lineage 3 Populations of this lineage increase from mean M J length from 7.55 to 8.36 while M E L randomly ranges between 4.94 and 5.13. Rise of intraspecific competition is sufficient to explain the increase of size. Intraspecific competition tends to inorease infant probability of death favouring a selection of individuals with larger size and a faster body development. External factors could also be invoked but strongly focused interactions must be envisaged.
Lineage 2 This is the lineage that is believed to be indigenous and to be present in all fissures. We think that there are not sufficient reasons in Freudenthal, 1976, to place the smallest form, Microtia parva of the Biancone fissure, at the base of the lineage. Derivation f r o m the largest one, Microtia maiuscola, is equally possible. Mean of M 9 length ranges from 3.15 to 6.75 in the whole sequence, in the younger fissure group it starts from 5.59. M E L reaches the mean value of 6.4. Along this lineage there is not only size increase but also a continuous morphological evolution in M t and M3. Other than in lineage 3 the evolutionary strategy o f lineage 2 must be explained with more complex interrelationships. Along this lineage size increase alone was not a sufficient reward. Evidently increase of chewing efficiency was also needed. Really morphological evolution can not be charged to internal factors as sister lineages stop at M E L 5. Also intraspecific competition does not seem enough. An active external competitors must be envisaged in Prolagus. 6. It is evident that these hypotheses need to be verified and refined with more analysis and field work. It is clear in any case that the Gargano is a wonderful natural l a b o r a t o r y for studying p h e n o m e n a of microevolution and of ecological interrelationships among different species. Also effects of the changing areal extent can be probably tested.
REFERENCES
AZZAROLI A., DE GIUL1 C., FICCARELLI G. & TORRE D. (1982) - Table of the stratigraphic distribution of terrestrial mammalian faunas in Italy from the Pliocene to the early middle Pleistocene. Geogr. Fis. Dinam. Quat., 5, 55-58.
DE GIULI C. & TORRE D. (1983) - A microfauna with Allophaiomys pliocaenicus from Gargano (Southern Italy). Palaeont. It. (in press).
BALLMANN P. (1973) - Fossile VOgel aus deg Neogen der Halbinsel Gargano (Italien). Scripta GeoL, 17, 1-75.
FREUDENTHAL M. (1972) - Deinogalerix koenigswald, nov. gen., nov. sp., a giant insectivore from the Neogene of Italy. Scripta GeoL, 14, 1-19.
BALLMANN P. (1976) - Fossile VOgel aus dem Neogen der Halbinsel Gargano (Italien), zweiter Teil. Scripta Geol., 38, 1-59.
FREUDENTHAL M. (1973) - Ein Riesenigel aus dem Neogen Italiens. Natur u. Museum., 103, 427-430.
BUTLER P.M. (1981) - The giant erinaceid insectivore, Deinogalerix FREUDENTHAL, from the Upper Miocene of Gargano, Italy. Scripta Geol, 57 (1980), 1-72.
FREUDENTHAL M. (1971) - Neogene vertebrates from the Gargano Peninsula, Italy. Scripta Geol., 3, 1-10.
FREUDENTHAL M. (1976) - Rodent stratigraphy of some Miocene fissure fillings in Gargano (prov. Fog#a, Italy). Scripta Geol., 37, 1-23.