Reaction of lizard populations to a catastrophic wildfire in a central Arizona mountain range

Biological Conservation 107 (2002) 193–201 www.elsevier.com/locate/biocon

Reaction of lizard populations to a catastrophic wildfire in a central Arizona mountain range Stan C. Cunninghama,*, Randall D. Babba, Thomas R. Jonesb, Bruce D. Tauberta, Raul Vegaa a

Arizona Game and Fish Department, 2221 W. Greenway Road, Phoenix, AZ 85023, USA b Grand Canyon University, 3300 W. Camelback Road, Phoenix, AZ 85061, USA

Abstract In April 1996, the Lone Fire denuded over 90% of the vegetation in 130 km2 around the Four Peaks area of the Mazatzal Mountains in central Arizona. To understand the reaction of a relatively immobile guild of species to a wildfire, we pit-trapped lizards from 1996 to 1999 in both burned and unburned interior chaparral and Madrean evergreen forest. In 26,214 trap nights, we found relative abundance was up to 10 times greater in burned than unburned vegetation. Species richness and diversity values were also greater in burned sites. Our data indicate a rapid settlement of burned areas primarily by individuals that survived the fire. Increased capture rate, diversity and richness values in 1998 and 1999 indicate that many species of lizards may even prefer early successional stages in chaparral and Madrean evergreen forests. Resident species of Teiidae and Sceloporus undulatus were more adapted to disturbed habitats than other resident Phrynosomatidae or Crotophytidae. # 2002 Published by Elsevier Science Ltd. Keywords: Arizona; Crotophytidae; Chaparral; Fire; Lizards; Madrean Evergreen Forest; Phrynosomatidae; Sky Island; Succession; Teiidae

1. Introduction Fire history studies (circa 1650–1900), indicate that forests in southwestern United States mountain ranges burned every 2–10 years, much more frequently than observed today (Swetnam and Betancourt, 1990). This fire regime ensued from an annual cycle of a wet winter (November–February), a normal arid foresummer (April–June), and lightning storms before the onset of summer monsoonal rains (July–September). Baisan and Swetnam (1990) found that in coniferous forests at higher elevations in the Rincon Mountains (sky islands), Arizona, the historical fire regime from 1697 to 1860 was dominated by large scale (> 200 ha), early season (May–July) surface fires every 1 to 13 years. This cycle has changed due to changes in land use, removal of fine fuels by livestock grazing, and fire suppression (Swetnam and Betancourt, 1990). With fire exclusion, dead fuels accumulated continuously, and dense thickets formed in interior chaparral and invaded open ponderosa pine (Pinus ponderosa) stands, which increased hazard for catastrophic crown fires or stand replacing fires (Fule and Covington, 1994). These stand replacing fires are * Corresponding author. Tel.: +1-602-942-3000. E-mail address: [email protected] (S.C. Cunningham).

probably a recent phenomenon (41 century) because constantly accumulating fuels have no other means of elimination (Fule and Covington, 1994). On 28 April 1996 a wildfire (the Lone Fire) started on Four Peaks in the central Mazatzal Mountains, Arizona and burned for 16 days. The Lone Fire burned 130 km2 and destroyed > 90% of the vegetation. The Four Peaks area is typical of southwest desert mountain ranges that are considered sky islands, with ponderosa pine and mixed conifer at higher elevations surrounded by interior chaparral and Sonoran desert scrub at the lowest elevations. This stand replacement fire, resulting in high vegetation mortality, could be considered ‘‘ecologically unnatural’’ considering historically frequent fires burned mountain top forests without mature tree mortality (Fule and Covington, 1994). Many land management agencies support a ‘‘let burn’’ policy without understanding effects of a stand replacing fire on relatively immobile guilds such as reptiles. In Florida sandhill communities, Mushinsky, 1985, found that some species benefited from high fire frequency (i.e. Cnemidophorous sexlineatus), while others were negatively impacted (Eumeces inexpectatus; Mushinsky, 1992). Arizona interior chaparral and forest communities have high lizard species diversity along with historically high fire frequencies, but we have little

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information on post-fire reptile communities in the southwestern United States. Lizard density and community structure can vary widely over short time periods (seasons or years) and according to changes in moisture, food, or other resources (Andrews, 1991; James, 1994; Tinkle et al., 1993). Although we believe our data reflect changes mostly attributable to those associated with fire, other factors acted concurrently. Nonetheless, we address several issues: (1) Were lizard communities (abundance, richness, diversity) different between burned and unburned vegetation types? (2) Are community trends evident? (3) Are changes a result of survival or immigration? (4) Can the natural history of species help explain changes? and (5) can differences be related to vegetation cover changes?

2. Study area The 245 km2 study area was 80 km northeast of Phoenix AZ in the southern portion of the Mazatzal Mountains (Fig. 1). Elevations ranged from 720 to 2300 m, with steep, rocky topography, and many slopes > 45%. Annual precipitation averaged 63 cm and occasional snows usually melted within a week. Temperatures ranged from
5  C in winter to > 39  C in summer. There is a fairly constant precipitation gradient of 1 cm/300 m and 1  C/100 m change in elevation (Sellers and Hill, 1974). The primary vegetative type is interior chaparral (Brown and Lowe, 1974), a complex association of shrubs and low trees. One to two shrub species often dominate locally but > 50 chaparral species were identified during our study. Chaparral intergrades with Arizona upland desert scrub and semi-desert grassland at lower elevations. Both Four Peaks and Mt. Ord have Madrean evergreen woodland and Ponderosa pine montane coniferous types at higher elevations. Major drainages contained riparian communities composed of both deciduous and evergreen trees.

3. Methods We selected four vegetation types to examine possible differences in lizard communities: burned chaparral, unburned chaparral, burned forest, and unburned forest. Within burned chaparral on Four Peaks we established transects located at distances of 0.2, 0.4, 1.3, and 2.8 km from the edge of the burn. In burned forest on Four Peaks, we sampled at 1.0, 4.3, 4.8, and 5.0 km from the burn perimeter. We sampled unburned forest and chaparral on Mt. Ord and unburned sections of both vegetation types on Four Peaks. Lizards were sampled using three to four permanent transects of five arrays each in each of the four treatment

types. Each array consisted of four 13.3-l buckets separated by 5 m in a ‘‘Y’’ pattern, with a 20 cm tall drift fence connecting buckets (Bury and Corn, 1987). Plywood lids were positioned 3 cm above bucket rims, supported by rocks, to protect trapped animals from desiccation and attract animals looking for cover. Buckets were checked a minimum of every 3 days from: 3 September to 1 October 1996, 23 June to 28 September 1997, 7 July to 6 October 1998, and 20 July to 29 October 1999. There were > 8000-bucket days from 1997 to 1999 resulting in 26,214 total trap days. We used linear regression to test if lizard species abundance (No. of lizards captured/100 bucket days) or richness (No. of lizard species) were correlated with distance from burn perimeter or elevation within each vegetation type. Species abundance and richness were computed overall (end of season) and at the end of each 8-day trapping period. We used Shannon’s H 0 to measure diversity and Hill’s N2, which reports the number of ‘‘mathematically’’ abundant species. We used Hill’s E5 to measure evenness of different species distributions within each treatment. A Kruskal–Wallis Test was used to test differences among vegetation types and years with respect to abundance, richness, diversity, and evenness. To test if lizard community characteristics were similar in unburned treatments on Four Peaks versus Mt. Ord, we used a Mann–Whitney U test. Differences were considered significant when P < 0.05. Although we expected some differences we chose a simple null hypothesis, for statistical comparison, that lizard community characteristics did not differ between burned and unburned vegetation. At the first array of each transect we ran a 25 m line intercept vegetation transect, oriented to the landscape contour, in the first week of September each year. Herbaceous cover was sampled at the following height intervals: 0–0.15, 0.16–0.30, 0.31–0.91, 0.9–1.8, 1.9–4.6, and > 4.6 m. Dead or burned vegetation was not recorded. Stepwise multiple linear regression was used to compare overall abundance, abundance of western whiptail lizards (Cnemidophorus tigris) and eastern fence lizards (Sceloporus undulatus), and species richness with cover values at different height intervals.

4. Results Our initial study design assumed lizard community characteristics in unburned vegetation types on Mt. Ord and Four Peaks would be similar. However, Mt. Ord had significantly lower species abundance (U=68.5, P < 0.001) and richness (U=52.5, P < 0.001) in both unburned chaparral and forest. We found no vegetation cover or microsite differences, but lizard abundance on Mt. Ord was less than half that on Four Peaks each year. Mt. Ord species richness was 7, compared to 17 on

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195

Fig. 1. Map of the study area in the Mazatzal Mountains, Arizona, 1997–1999, including the fire boundary, Four Peaks and Mt. Ord sky islands, and the locations of each pitfall trap array.

Four Peaks. Therefore, in comparisons below, we used only Four Peaks data for comparisons of burned and unburned vegetation types. 4.1. Community values among vegetation types Lizard abundance differed significantly (X2=21.6, P < 0.001) among all vegetation types with all years combined. Abundance differed significantly among

vegetation types in 1997 and 1998, but not 1999. Unburned chaparral abundance was 50–75% lower than burned chaparral in 1998 and 1997, respectively. Lizard abundance was greater in burned chaparral (x=14.4%) and burned forest (11.7%) than unburned chaparral (6.1%) and unburned forest (2.8%). Lizard species richness among treatments was significantly different (2=9.6, P=0.02) with all years combined, but did not differ within any year of study.

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Burned chaparral species richness was the highest value each year among vegetation types. Mean species richness in unburned forest (x=5) was less than half that captured in burned chaparral (14.7), burned forest (11.7), or unburned chaparral (12.3; Fig. 2). Diversity (H 0 ) differed (2=8.4, P=0.04) among vegetation types with all years combined and was highest in burned and unburned chaparral, and lowest in unburned forest (Table 1). Number of abundant species (N2) also differed (2=9.3, P=0.02) and was highest in unburned chaparral (x=5.9) and lowest in unburned forest (x=1.7). Evenness was similar in all vegetation types. The ratio of immatures:adults captured increased through September each year, but the difference was never significant. Limited 1996 data, collected in September only, were similar to 1997–1999. Lizard abundance was greatest in burned sites, particulary in burned chaparral. The proportion of immatures was higher in burned vegetation also. Consistent among all vegetation types was the greatest number of captures in 1998. However we found no correlation with vegetation or weather. There were no significant differences in precipitation, maximum and minimum daily temperatures, or monthly averages among years. 4.2. Chaparral Burned chaparral abundance was significantly different (2=14.4, P=0.001) among years (Table 1) and highest in 1998 (18%) and lowest in 1999 (5%). Species richness was similar between years, and 14 species were captured overall. In burned chaparral, correlations between distance from the perimeter of the burned plot

Fig. 2. Histogram of lizard species richness in each of the four treatments in the Mazatzal Mountains, Arizona, 1997–1999.

and abundance and species richness were both significant (P=0.03), but weak (r2=0.08 and 0.16, respectively). C. tigris seemed to benefit most from the burn, as they were the most common species captured in burned chaparral (52%, Table 2), and were 8 times more numerous than in unburned chaparral. Four other Teiidae species, Sonoran spotted whiptail (Cnemidophorus sonorae), Gila spotted whiptail (Cnemidophorus flagellicaudus), plateau striped whiptail (Cnemidophorus velox), and little striped whiptail (Cnemidophorus inornatus) were also considered abundant (N2). S. undulatus was the second most common species, and along with tree lizards (Urosaurus ornatus), were the only Phrynosomatidae considered abundant (N2). U. ornatus was captured 55 times in burned chaparral, only four times in unburned. The numbers of most lizards captured declined in 1999, and the proportion of C. tigris captured declined from 1996 to 1999 (65–32%). Diversity and evenness increased as the proportion of C. tigris declined. Abundance in unburned chaparral differed significantly (2=14.3, P=0.001) among years and was highest in 1998 and lowest in 1997. Unburned chaparral

Table 1 Lizard community values as determined from pitfall captures in burned and unburned chaparral, and burned and unburned forest in the Mazatzal Mountains, Arizona, 1997–1999 Treatment

1997

1998

1999

Burned chaparral N No. lizards/trap day Species richness Species evenness E5 Shannon’s H0 Hill’s N2

2120 0.12 15 0.47 1.5 2.6

2220 0.18 14 0.47 1.4 2.5

2100 0.05 15 0.71 2.1 6.1

Unburned chaparral N No. lizards/trap day Species richness Species evenness E5 Shannon’s H0 Hill’s N2

1570 0.03 13 0.79 2.0 6.6

1640 0.09 12 0.53 1.4 6.6

2100 0.04 12 0.45 1.9 4.5

Burned forest N No. lizards/trap day Species richness Species evenness E5 Shannon’s H0 Hill’s N2

1,900 0.09 13 0.4 1.2 1.9

2160 0.14 12 0.5 1.4 2.5

3064 0.09 10 0.48 1.4 2.4

Unburned forest N No. lizards/trap day Species richness Species evenness E5 Shannon’s H0 Hill’s N2

2220 0.02 4 0.52 0.7 1.5

2140 0.03 4 0.6 0.7 1.5

2980 0.01 7 0.52 1.1 2.1

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Table 2 Number of each lizard species, listed in order of abundance, captured from 1996 to 1999 in burned chaparral post Lone Fire in the Mazatzal Mountains, Arizonaa Species Common name Cnemidophorus tigris Western Whiptail Sceloporus undulatus Eastern Fence Lizard Urosaurus ornatus Tree Lizard Cnemidophorus sonorae Sonoran Spotted Whiptail Cnemidophorus flagellicaudus Gila Spotted Whiptail Cnemidophorus velox Plateau Striped Whiptail Cnemidophorus inornatus Little Striped Whiptail Coleonyx variegates Banded Gecko Holbrookia texana Greater Earless Lizard Crotaphytus collaris Collared Lizard Cnemidophorus uniparens Desert-Grassland Whiptail Eumeces obsoletus Great Plains Skink Sceloporus magister Desert Spiny Lizard Phrynosoma douglassi Short Horned Lizard a

1996

1997

1998

1999

Total captured

25 (23)

148 (79)

250 (136)

34 (6)

357 (244)

6 (6)

39 (30)

62 (38)

17 (11)

124 (85)

1 (0)

4 (4)

37 (32)

3 (1)

45 (37)

2 (0)

1 (1)

15 (7)

16 (7)

34 (15)

0

16 (8)

1 (1)

11 (0)

28 (9)

2 (0)

9 (4)

13 (3)

3 (1)

27 (8)

0

12 (11)

10 (4)

4 (0)

26 (15)

0

5 (0)

9 (9)

8 (0)

22 (9)

1 (1)

4 (4)

2 (2)

3 (1)

10 (8)

1 (1)

2 (2)

5 (5)

0

8 (8)

0

0

0

3 (3)

3 (3)

0

1 (0)

1 (0)

1 (1)

3 (1)

0

1 (0)

0

1 (1)

2 (1)

0

0

1 (1)

0

1 (1)

Numbers in ( )=number of immatures. Numbers in bold represent abundant species as determined from N2 calculations.

was the only vegetation type where species richness differed among years (2=6.1, P=0.005), and 16 species were captured overall. S. undulatus was captured most often each year (48%; Table 3), followed by C. tigris (19%). Collared lizards (Crotaphytus collaris) were abundant (N2) in 1997–1998 in unburned chaparral. Similar to burned chaparral, Teiidae were common. C. tigris, C. inornatus, and C. velox were abundant (N2) each year and overall. Short horned lizards (Phrynosoma douglassi) made up a greater proportion of captures in unburned (3%) than burned chaparral (0.1%). 4.3. Forest The greatest difference in lizard communities was seen in burned forest. Lizard abundance was second highest in burned forest each year, and 4–9 times greater overall than unburned forest. Abundance values differed significantly (2=7.5, P=0.03) among years. The correlation between distance to edge of burn and abundance was significant (P=0.04), but r2 was low (0.18) and the standard error was high (5.3). Fourteen species were captured in burned forest, the most common being S. undulatus (63%) and C. inorna-

tus (13%, Table 4), which were abundant (N2) each year. C. velox was abundant (N2) in 1998. All six Teiidae were captured in burned forest, and C. inornatus and C. velox were the most numerous. S. undulatus, and U. ornatus were the most common Phyrnosomatidae, and U. ornatus were 20 times more common in burned forest than unburned. Lizard species and number captured in burned, but not unburned forest included C. sonorae (16) C. collaris (11), Coleonyx variegatus (7), C. gila (7), C. tigris (7), and Eumeces obsoletus (4). Unburned forest had the lowest values for lizard abundance, richness, and diversity each year and overall. Abundance differed significantly (w2=7.8, p=0.02) among years. S. undulatus (78%) and C. inornatus (9%) were the most frequently captured lizards in unburned forest (Table 5), and both were calculated as abundant. From N2 calculations, P. douglassi were abundant in 1997, and Madrean alligator lizards (Elgaria kingi) were abundant in 1999. 4.4. Correlation with vegetation and topography Vegetation cover was similar each year in both unburned sites, but increased each year within burned

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Table 3 Number of each lizard species, listed in order of abundance, captured from 1996 to 1999 in unburned chaparral post Lone Fire in the Mazatzal Mountains, Arizonaa Species Common name Sceloporus undulatus Eastern Fence Lizard Cnemidophorus tigris Western Whiptail Cnemidophorus inornatus Little Striped Whiptail Cnemidophorus velox Plateau Striped Whiptail Crotaphytus collaris Collared Lizard Phrynosoma douglassi Short Horned Lizard Cnemidophorus flagellicaudus Gila Spotted Whiptail Eumeces obsoletus Great Plains Skink Cnemidophorus sonorae Sonoran Spotted Whiptail Urosaurus ornatus Tree Lizard Cnemidophorus uniparens Desert-Grassland Whiptail Sceloporus magister Desert Spiny Lizard Coleonyx variegates Banded Gecko Heloderma suspectum Gila Monster Holbrookia texana Greater Earless Lizard Elgaria kingi Madrean Alligator Lizard a

1996

1997

1998

1999

Total captured

4 (1)

18 (12)

81 (58)

35 (19)

138 (90)

0

11 (4)

32 (21)

9 (0)

52 (25)

0

6 (2)

7 (2)

6 (4)

19 (8)

0

2 (0)

6 (3)

9 (3)

17 (6)

0

3 (2)

5 (1)

0

8 (3)

1 (0)

1(1)

1 (1)

5 (0)

8 (2)

0

0

0

7 (1)

7 (1)

0

1 (0)

3 (3)

2 (2)

6 (5)

0

0

5 (3)

1 (1)

6 (4)

0

1 (1)

0

3 (2)

4 (3)

0

0

2 (2)

1 (0)

3 (2)

0

2 (1)

0

0

2 (1)

0

0

1 (1)

0

1 (1)

0

0

0

1 (1)

1 (1)

0

1 (0)

0

0

1 (0)

0

1 (0)

0

0

1 (0)

Numbers in ( )=number of immatures. Numbers in bold represent abundant species as determined from N2 calculations.

vegetation as succession increased. In a series of stepwise regression models, independent variables included vegetation cover at each height interval, elevation, and vegetation type. Dependant variables included all species abundance, richness, and C. tigris and S. undulatus abundance. No correlations were found with respect to abundance and richness of all species. In the C. tigris abundance model, we found a significant inverse relationship with elevation (r2=0.92), but no combination of vegetation cover was important. We also found a correlation between S. undulatus abundance and vegetation type (burned forest). A Kruskal– Wallis test determined that S. undulatus abundance differed (2=13.4, P=0.004) among vegetation types.

5. Discussion The Lone Fire temporarily denuded vegetation in chaparral and forest but lizard abundance, richness, and

diversity increased in burned areas. The greatest increase was in burned forest. Among vegetation type variability was greater than among years variability. Natural history characteristics including foraging strategy and diet, home range size, reproductive strategy (number of eggs and clutches, unisexual versus bisexual), habitat, and shelter requirements could all effect lizard species reestablishment rates into a floristically denuded area. In the absence of experimental manipulation, we cannot address many of these relationships, but our data allow insight into initial settlement. Lizard abundance of different species, sexes, and age classes, species richness and diversity has been directly correlated with vertical and horizontal vegetation diversity (Pianka, 1966, 1973), amount of thermal cover (Adolph, 1990), and presence or absence of certain plant species (Szaro and Belfit, 1986). Hence, we expected initial destruction of vegetation to inhibit rather than increase lizard abundance. However, abundance and diversity were highest in burned sites from 3 months

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Table 4 Number of each lizard species, listed in order of abundance, captured from 1996 to 1999 in burned forest post Lone Fire in the Mazatzal Mountains, Arizonaa Species Common Sceloporus undulatus Eastern Fence Lizard Cnemidophorus inornatus Little Striped Whiptail Urosaurus ornatus Tree Lizard Cnemidophorus velox Plateau Striped Whiptail Cnemidophorus sonorae Sonoran Spotted Whiptail Phrynosoma douglassi Short Horned Lizard Elgaria kingi Madrean Alligator Lizard Crotaphytus collaris Collared Lizard Coleonyx variegates Banded Gecko Cnemidophorus flagellicaudus Gila Spotted Whiptail Cnemidophorus tigris Western Whiptail Eumeces obsoletus Great Plains Skink Cnemidophorus uniparens Desert-Grassland Whiptail a

1996

1997

1998

1999

Total captured

13 (12)

122 (96)

179 (105)

136 (91)

450 (304)

0

13 (8)

56 (36)

23 (9)

92 (53)

0

20 (15)

7 (7)

16 (9)

43 (31)

0

1 (0)

15 (5)

18 (5)

34 (10)

0

4 (2)

1 (1)

11 (3)

16 (6)

0

3 (2)

8 (7)

3 (1)

14 (10)

0

2 (1)

12 (1)

0

14 (2)

0

2 (2)

9 (9)

0

11 (11)

0

0

7 (7)

0

7 (7)

0

0

0

7 (1)

7 (1)

0

3 (2)

3 (1)

1 (0)

7 (3)

0

0

4 (4)

0

4 (4)

0

0

0

3 (1)

3 (1)

Numbers in ( )=number of immatures. Numbers in bold represent abundant species as determined from N2 calculations.

post fire to > 3 years later, indicating rapid recovery and a possible preference for disturbed sites. In 1996 there was little to no ground cover, and despite rapid succession, there was still little vegetation cover > 1.9 m above ground through 1999. An increase in food resources (insects) could be expected due to dead wood and increase in grasses and forbs. Lizards in southern California both increased and shifted home ranges to take advantage of post-fire food resources (Kahn, 1960; Lillywhite and North, 1974; Lillywhite, 1977). Food resource increase can directly influence lizard density and species diversity (Pianka, 1973; Vitt et al., 1981) and may override shelter and microsite needs. The lack of relationship between species abundance and vegetation cover may indicate a greater plasticity in microhabitat selection than expected, an insufficient amount of vegetation sampling, or a combination of both. Our vegetation sampling ignored dead material including charred stumps, downed trees, and branches. Arboreal species that use tree or shrub base structures (e.g. Sceloporus spp., Pianka, 1966) were probably able to use charred stumps and they were more numerous than those that use outer branches (e.g. Urosaurus spp.). Obviously, burned areas had enough microsites, food

resources, and cover for more species, both sexes and several age classes to coexist and increase. We expected a fire as destructive as the Lone Fire to kill most resident lizards and colonization to be primarily by immigrants. Both Chew et al. (1959) and Simons (1989) found that small vertebrates were more likely to be killed directly by a fire than larger vertebrates, however, others have documented small animal survival (Kahn, 1960; Lawrence, 1966). However, our data indicate primarily fire survivors were the majority of founders for post-fire lizard communities. The Lone Fire occurred prior to lizard species laying eggs, so the high presence of juveniles in burned sites in 1996 indicates survivorship of adults. We captured more lizards in burned than adjacent unburned sites 3 months after the fire, and many juveniles were captured > 4 km from the edge of the burn. The lack of a strong relationship between distance to fire edge and lizard abundance and richness also suggests high survival. Whiptail lizards (active foragers with large home ranges) were the quickest and most successful group of species post-fire. These widely foraging species should be least limited by vegetation microsites. Whiptail lizards inhabit a wide variety of habitats and show both inter- and intra-specific adaptations to changing

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Table 5 Number of each lizard species, listed in order of abundance, captured from 1996 to 1999 in unburned forest post Lone Fire in the Mazatzal Mountains, Arizonaa Species Common Sceloporus undulatus Eastern Fence Lizard Cnemidophorus inornatus Little Striped Whiptail Elgaria kingi Madrean Alligator Lizard Phrynosoma douglassi Short Horned Lizard Cnemidophorus velox Plateau Striped Whiptail Urosaurus ornatus Tree Lizard Holbrookia maculata Lesser Earless Lizard Cnemidophorus uniparens Desert-Grassland Whiptail Sceloporus clarki Clark’s Spiny Lizard a

1996

1997

1998

1999

Total captured

8 (7)

40 (12)

58 (41)

20 (6)

126 (66)

0

2 (2)

13 (8)

0

15 (10)

0

3 (2)

0

4 (0)

7 (2)

0

5 (3)

0

1 (1)

6 (4)

0

0

2 (1)

0

2 (1)

0

0

1 (1)

1 (0)

2 (1)

0

0

0

1 (1)

1 (1)

0

0

0

1 (0)

1 (0)

0

0

0

1 (1)

1 (1)

Number in ( )=number of immatures. Numbers in bold represent abundant species that period as calculated from N2 calculations.

environmental conditions (Pianka, 1970; Vitt et al., 1997; Eifler and Eifler, 1998). The two most common whiptail lizards (C. tigris and C. inornatus) are bisexual species, and the four less common are unisexual. If mortality during the fire was high, we would have expected unisexual species to have an advantage, if not, we should have seen numbers of bisexual species at least remain stable. C. tigris and C. inornatus were most abundant in burned chaparral and forest, and the increase in adult and juvenile abundance in burned sites indicates little fire mortality and no problem finding mates. Thus, there was no reproductive advantage for unisexual species over species requiring sex to reproduce. In experimental studies, Massot et al. (1992, 1994) found a prior-residence advantage in ability of individuals to face a new environment. Wright and Lowe (1968) pointed out that all-female Cnemidophorus primarily occupied disclimax, perpetually disturbed, marginal, or ecotone habitats. The Lone Fire was not enough of a disturbance to affect bisexual C. tigris and C. inornatus, at least in the short-term. The larger home range of the S. undulatus may enable individuals to find density sinks more frequently (M’Closkey and Hecnar, 1994). Conversely, the small territory size and arboreal nature of the U. ornatus could limit them finding these same density sinks and may explain our abundance differences between the two species. Phrynosomatidae also show a large amount of variation in life history characteristics (size, reproduction, etc.), depending on quality and characteristics of the habitat (Adolph, 1990; Grant and Dunham, 1990).

The reduced lizard numbers and species on Mt. Ord as compared to Four Peaks were an unexpected, but significant finding. Pre Lone Fire, Four Peaks was a larger forested island (51 km2) than Mt. Ord (17.7 km2). Jones et al. (1985) found mountain island size affected lizard species richness and that species richness on smaller islands were subsets of species from similar larger islands, which we also noted. However, since chaparral is contiguous from Four Peaks to Mt. Ord, this would not explain the difference in richness and abundance in chaparral. Another factor could be that Four Peaks is closer to a greater area of Arizona upland desert scrub than Mt. Ord. Many of the species we recorded large numbers of are common in Arizona upland desert scrub (Stebbins, 1966). We stress a careful interpretation of these results, as these are only short-term affects, and other variables could have affected lizards concurrently. We predict that there may be different results for species more common in forests than chaparral. In 4 years since the fire, we have not noted any ponderosa pine reproduction, and the forest may not be able to recover from this type of fire (Swetnam et al., 1999). The long-term effect of reduction in size of a ponderosa pine located on top of the mountain will not be determined for many years. Jones et al. (1985) and our data of reduced lizard abundance, richness, and diversity on a smaller forested sky island (Mt. Ord) may indicate the future for pine forest adapted lizard species on Four Peaks. Germano and Hungerford (1981) found a significant reduction in several species of lizards in an area where mesquite trees

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had been cleared 22 years prior to their surveys. We would expect continued growth of chaparral communities to reduce abundance, but not species richness of lizards. This habitat type and the abundance of species within it could even be classified as ‘‘fire dependent’’ given the history of frequent chaparral burnings. Our data indicate that prescribed burning designed to preserve sky island forests will not negatively affect lizard abundance and richness. In fact, our short-term data indicate it could increase lizard populations. Further research needs to be conducted on effects of cooler prescribed burns on chaparral and forested lizard species.

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