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27 April 2011 



Number 522 



AN ECOMORPHOLOGICAL ANALYSIS OF NATIVE AND INTRODUCED 
POPULATIONS OF THE ENDEMIC LIZARD ANOLIS MA YNARDI OF THE 

CAYMAN ISLANDS 

Anthony Herrel^, Matt DaCosta Cottam^, Kristan Godbeer^, Thomas Sanger^, and 

Jonathan B. Losos^ 

Abstract. Anolis maynardi is an endemic anole from Little Cayman (Cayman Islands) that is characterized by an 
extremely elongated rostrum in males. In the 1980s, this species was discovered on the nearby island of Cayman Brae 
where it was likely introduced. Despite its unusual morphology and endemic status, little is known about the 
abundance, ecology, or natural history of this species. Our data suggest that animals from the two islands are distinct 
in their morphology, performance, and ecology: Cayman Brae lizards utilize more open habitats, have relatively 
longer limbs and shorter heads, but higher bite forces on average. Moreover, a distinct sexual dimorphism is present 
in both populations in which males have relatively larger heads and longer limbs than females. 



INTRODUCTION 

Anolis maynardi is endemic to the small 
(28 km2) island of Little Cayman. Typical of 
other members of the carolinensis species 
group, and of "trunk-crown" ecomorphs in 



'UMR 7179 C.N.R.S/M.N.H.N., Departement d'Eco- 
logie et de Gestion de la Biodiversite, 57 rue Cuvier, 
Case postale 55, 75231, Paris Cedex 5, France; e-mail: 
anthony.herrel@mnhn.fr 

"Department of the Environment, 580 North Sound 
Road, Cayman Islands Environment Centre, P.O. Box 
486, Grand Cayman, Cayman Islands KYI -1106. 
^ Department of Organismic and Evolutionary Biology, 
Harvard University, 26 Oxford Street, Cambridge, Massa- 
chusetts 02138, U.S.A. 



general (Williams, 1983; Losos, 2009), this 
primarily arboreal species is green with the 
ability to change color to brown, and has 
relatively short legs and large toepads. Anolis 
maynardi is notable in one respect, however: 
it has an enormously elongated, pincer-like 
rostrum that is equaled in anoles only by 
Anolis longiceps of Navassa Island, to which 
A. maynardi may be closely related (Glor et 
ah, 2005). Why this unusual rostral mor- 
phology has evolved in these species is 
unknown. 

Indeed, almost nothing is known about the 
natural history of A. maynardi. Chapman 
Grant in "The Herpetology of the Cayman 



The President and Fellows of Harvard College 2011. 



BREVIORA 



No. 522 



Islands" (1940) stated that "It is stealthy in 
movements, apparently stupid... a tree lizard 
occasionally found on the ground; when in a 
tree it faces upwards showing that its prey is 
aboreal (sic)..." Seidel and Franz (1994) 
found that "it appears to be extremely 
arboreal and escapes to the upper portions 
of trees or buildings when pursued... the 
forceps-shaped snout suggests some unique 
feeding adaptation." Henderson and Powell 
(2009) also report that this species is usually 
arboreal and occurs on a wide variety of 
perches, including roadside bushes, cactus, 
and agave. Losos and de Queiroz (1997) 
recorded males perching on average 2.5 m 
above the ground on perches 11 cm in 
diameter. 

The distribution of A. maynardi on Little 
Cayman has also received little attention. 
Grant (1940) reported that this species may 
be more common in thicker vegetation and 
on the northern side of the island. Al- 
though the equally small island of Cayman 
Brae lies only 7.5 km distant from Little 
Cayman, A. maynardi never colonized this 
island. However, Franz et al. (1987) dis- 
covered the species in the vicinity of the 
airstrip on Cayman Brae, and in 1991, this 
was the only location on the island where 
the species was detected (Losos et al, 
1993). No further reports of the fate of 
this introduced population exist in the 
literature. 

Given that so little is known about the 
natural history of this morphologically un- 
usual species, we visited Little Cayman and 
Cayman Brae in April 2009 to collect basic 
data on the occurrence and distribution of 
the species in its native habitat on Little 
Cayman, provide an estimate of its abun- 
dance in optimal habitat patches, and 
compare native and introduced populations 
with respect to morphology, ecology, and 
performance. Finally, we also examined 
differences between the sexes in morphology. 



performance, and ecology to better under- 
stand the potential role of the unique 
elongated rostrum in males. 

MATERIALS AND METHODS 

Field sites 

Data were collected on Little Cayman 
5-10 April 2009 and on Cayman Brae 
10-15 April 2009. Sites throughout the 
island of Little Cayman were surveyed for 
the presence of A. maynardi to estimate its 
distribution across the island. Global 
positioning system coordinates were re- 
corded at all localities where animals were 
observed. 

Temperature 

Animals were caught by noose or by hand 
and body temperature was measured for all 
lizards that were caught immediately using a 
quick-reading thermometer (Miller and We- 
ber, Inc.). The air temperature was then 
measured at the site the lizard was first 
observed. 

Morphometries 

Animals were taken back to the field 
laboratory where they were weighed (Scout 
Pro balance) and measured using digital 
calipers (Mitutuyo). For each individual, 
we measured the following: head length, 
from the back of the parietal to the tip of 
the snout; head width, the width at the 
widest point of the head; head depth, the 
depth at the tallest part of the head; lower 
jaw length, the length of the lower jaw from 
the back of the retroarticular process to the 
tip of the lower jaw; jaw out-lever, the 
distance from the quadrate to the tip of the 
lower jaw; snout length, the distance from 
the back of the jugal to the tip of the lower 
jaw; interlimb length, measured between the 



2011 



ECOMORPHOLOGY OF A. MA YNARDI 



anterior edge of the sternum and the 
posterior edge of the pelvis; body width at 
the widest point; body depth at the shoulder; 
tail length; femur length; tibia length, meta- 
tarsal length; the length of the longest toe on 
the hind foot; humerus length; radius length; 
metacarpal length; and the length of the 
longest toe on the front foot. All measure- 
ments were taken on the left side of the 
animal and by the same observer. On the 
basis of these measures, four additional 
variables were calculated: the in-lever for 
jaw opening by subtracting the distance from 
the quadrate to the tip of the jaw from lower 
jaw length; the in-lever for jaw closing by 
subtracting the distance from the jugal to the 
jaw tip from the distance from the quadrate 
to the jaw tip; hind-limb length, the sum of 
all hind-limb segments; and forelimb length, 
the sum of all forelimb segments. 



(GV HD700) and recorded on tape. Subse- 
quently, clips were digitally transferred to the 
computer, cropped, and exported as jpg 
sequences. The snout tip was digitized on all 
sequences using Didge (A. CuUum, Creighton 
University, Omaha, Nebraska) and scaled 
coordinates were exported to Excel. Raw 
displacement profiles were calculated and 
smoothed using a fourth-order zero phase 
shift butterworth filter with cut-off frequency 
set at 30 Hz (Winter, 2004). Velocities were 
calculated through numerical differentiation 
of the smoothed displacement profile. Finally, 
the average speed over 20-cm intervals was 
calculated. The fastest 20-cm interval of the 
three trials was then considered an individu- 
al's maximal sprint speed. All trials were 
scored as good or bad and only trials that 
were scored as being "good" were retained for 
analysis. 



Bite force 

Bite force capacity was measured using an 
isometric Kistler force transducer (type 9203) 
mounted on a purpose-built holder and 
connected to a charge amplifier (type 5995; 
for details of the setup see Herrel et al., 
1999). Lizards were induced to bite the 
transducer five times, and the highest bite 
force recorded was used as an estimate of an 
individual's maximal bite performance. 

Sprint speed 

Sprint speeds were quantified for individ- 
uals on Cayman Brae only. Animals were 
filmed running up a 2-m-long dowel of 3 cm 
in diameter and placed at 45° using a portable 
Redlake Motion Meter (IDT, Tallahassee, 
Florida) camera set at 250 Hz. Three trials 
were recorded for each individual. In between 
trials, lizards were put in bags placed in half- 
sun, half-shaded conditions, allowing lizards 
to select their preferred temperatures. Video 
chps were streamed to a Sony HDV recorder 



Habitat use 

For every lizard caught, the following 
habitat characteristics were measured: 
perch height; perch diameter; distance to 
the nearest perch, defined as any part of the 
structural habitat upon which an animal 
could perch; and the diameter of this 
nearest perch. For each individual found 
sleeping during night surveys we recorded 
the perch height, perch diameter, and the 
type of substrate on which animals were 
sleeping. 

Population density estimates 

We searched a strip of habitat composed 
of sea grape (Coccoloba uvifera) trees 
between a coastal road and the sea on 
Little Cayman (extending 19.67441 32°N, 
80.0475083°W to 19.6732964°N, 80.0454- 
986°W) for sleeping A. maynardi. Individuals 
were marked with nontoxic paint markers to 
allow identification. On nights 2 and 3, we 
failed to recapture any previously marked 



BREVIORA 



No. 522 



lizards, but on night 4, we recaptured two 
individuals that had been previously marked. 
To make a preliminary population density 
estimate, we treated the first three nights as a 
single sampling session and the fourth night 
as a second sample and calculated popula- 
tion size using the Lincoln-Petersen method. 



green shrubland (Burton, 2008) and least 
abundant in mangroves. On the basis of our 
pilot mark-recapture study, we estimated a 
population density of 314 individuals in the 
surveyed patch of sea grape habitat. This 
leads to a density estimate of 0.06 animals 
per square meter. 



Analyses 

All morphological and habitat use data 
were logio-transformed before analysis to 
meet assumptions of normality and homo- 
scedasticity. To test for differences between 
sexes and populations (Little Cayman versus 
Cayman Brae), we first tested whether there 
were significant differences in body size using 
a two-way analysis of variance (ANOVA). 
Next, we tested for differences in head 
dimensions and bite forces using a multivar- 
iate analysis of covariance (MANCOVA) 
with snout-vent length as covariate. Similar- 
ly, we tested for differences in body and limb 
dimensions using a MANCOVA with snout- 
vent length as a covariate. Differences in 
habitat use and sleep site characteristics were 
tested using multivariate ANOVAs. In all 
cases, nonsignificant interaction effects were 
removed from our final model. An ANOVA 
was used to test for differences in sprint 
speed between the sexes. All analyses were 
performed in SPSS (v. 15.0). 

RESULTS 

Distribution and population density on 
Little Cayman 

We surveyed sites across the entire island 
covering all vegetation types to investigate 
the presence and distribution of A. maymirdi 
on Little Cayman. Animals were observed in 
all vegetation types, but densities appeared 
to differ considerably between the vegetation 
types; animals were most abundant in sea 
grape-dominated hcmisclerophyllous ever- 



Body size 

Males were larger on average than females 
on both islands (F, 52 = 499.89; P < 0.001), 
but lizards from the two islands did not 
differ in size (Fi,62 = 0.16; P = 0.69), nor 
was there an interaction between sex and 
island (Fi,62 = 1-54; P = 0.22; Table 1). 

Head dimensions and bite force 

Both sexes (Wilks' lambda = 0.52; F9 53 = 
2.54; P < 0.001) and islands (Wilks' lambda 
= 0.43; F9,53 = 7.89; P < 0.001) differed with 
respect to head dimensions and bite force, and 
the interaction term was marginally nonsig- 
nificant (Wilks' lambda = 0.74; Fg^ss = 2.06; 
P = 0.05). Subsequent univariate analyses of 
covariance testing for differences in intercept 
indicated significant differences between sexes 
in head length (Fi,6i = 27.90; P < 0.001), 
head width (Fi,6i = 5.61; P = 0.0.02), lower 
jaw length (Fi'gi = 39.84; P < 0.001), the 
distance from the quadrate to the tip of the 
snout (Fi,6i = 23.99; P < 0.001), and snout 
length (Fi,6i = 33.96; P < 0.001), with males 
having relatively longer and wider heads than 
females (Fig. 1; Table 1). No differences in 
slopes were observed. Animals from Little 
Cayman had longer and wider heads, but 
lower bite force, than animals from Cayman 
Brae for a given body size: head length (Fi (,1 
= 1 3.71 ; Z' < 0.001), head width (F,, 61 =7.75; 
P = 0.007), lower jaw length (F,,6i = 4.59; P 
= 0.04), the distance from the quadrate to the 
tip of the snout iF\j,\ = 5.35; P = 0.02), snout 
length (F|,6, = 7.00; P = 0.01), and bite force 
(F,,6i = 26.58; P < 0.001). 



2011 



ECOMORPHOLOGY OF A. MA YNARDI 



Table 1. Morphometric characterization of a native (Little Cayman) and introduced (Cayman Brac) 

POPULATION OF AnOLIS MAYNARDI. 





Little 


Cayman 






Cayman Brac 






Male (« = 14) 


Female (« = 13) 


Male 


[n = 30) 


Female (« = 9) 


Snout-vent length (mm) 


68.9 ± 3.1 


51.3 


± 3.1 


70.3 


± 3.5 


50.6 


± 1.5 


Body mass (g) 


6.6 ± 0.9 


2.5 


± 0.6 


6.5 


± 1.1 


2.8 


± 0.4 


Head length (mm) 


22.2 ± 1.2 


15.3 


± 0.7 


18.3 


± 2.0 


14.6 


± 0.5 


Head width (mm) 


10.0 ± 0.6 


6.9 


± 0.4 


9.9 


± 0.6 


6.7 


± 0.4 


Head depth (mm) 


7.1 ± 0.4 


5.1 


± 0.4 


7.3 


± 0.4 


5.0 


± 0.2 


Lower jaw length (mm) 


23.8 ± 1.5 


15.5 


± 0.9 


24.2 


± 1.5 


15.1 


± 0.5 


Quadrate tip (mm) 


21.7 ± 1.4 


14.2 


± 0.9 


22.0 


± 1.4 


13.7 


± 0.5 


Snout length (mm) 


18.2 ± 1.2 


12.0 


± 0.6 


18.5 


± 1.1 


11.6 


± 0.4 


Open in-lever (mm) 


2.2 ± 0.2 


1.3 


± 0.4 


2.2 


± 0.2 


1.4 


± 0.1 


Close in-lever (mm) 


3.5 ± 0.3 


2.2 


± 0.4 


3.5 


± 0.3 


2.1 


± 0.1 


Bite force (N) 


8.6 ± 1.6 


3.5 


± 0.9 


11.9 


± 2.5 


4.0 


± 0.6 


Body length (mm) 


31.9 ± 1.7 


25.2 


± 2,7 


32.8 


± 1.9 


25.5 


± 1.8 


Body width (mm) 


10.9 ± 0.9 


7.6 


± 0.9 


10.4 


± 1.1 


7.2 


± 0.7 


Body height (mm) 


9.2 ± 0.7 


6.4 


± 0.9 


9.5 


± 0.8 


7.0 


± 0.6 


Femur length (mm) 


13.0 ± 0.6 


9.6 


± 0.7 


13.2 


± 0.7 


9.2 


± 0.4 


Tibia length (mm) 


13.0 ± 0.6 


9.6 


± 0.7 


13.7 


± 0.6 


9.8 


± 0.3 


Metatarsus length (mm) 


8.2 ± 0.4 


6.0 


± 0.4 


8.4 


± 0.3 


5.9 


± 0.2 


Longest-toe hind limb (mm) 


9.7 ± 0.6 


7.4 


± 0.6 


10.4 


± 0.4 


7.3 


± 0.4 


Hind-limb length (ram) 


43.8 ± 1.8 


32.6 


± 2.1 


45.7 


± 1.7 


32.2 


± 0.8 


Humerus length (mm) 


11.4 ± 0.8 


8.1 


± 0.8 


11.4 


± 0.7 


8.0 


± 0.3 


Radius length (mm) 


9.4 ± 0.6 


6.7 


± 0.5 


9.7 


± 0.5 


6.0 


± 1.0 


Metacarpus length (nmi) 


3.6 ± 0.4 


2.8 


±0.3 


3.6 


± 0.3 


2.7 


± 0.3 


Longest-toe forelimb (mm) 


5.7 ± 0.4 


4.1 


± 0.3 


5.8 


± 0.4 


3.9 


± 0.3 


Forelimb length (mm) 


30.2 ± 1.6 


21.6 


± 1.6 


30.5 


± 1.4 


21.4 


± 0.7 


Sprint speed (ms~') 








1.5 


± 0.3* 


1.2 


± 0.2** 



"« = 16; **« = 9. Table entries are means ± standard deviations. 




Figure 1 . A, Picture of an adult male Anolis maynardi from Little Cayman in its native evergreen shrubland 
habitat illustrating the greatly elongated rostrum. (B) Picture of a male A. maynardi in the sea grape habitat where it 
was very abundant on Little Cayman. 



BREVIORA 



No. 522 



E 
E 



(0 

0) 





O 


Uttie Cayman - males 










o 


Little Cayman - females 








25 


• 


Cayman Brae - males 






•^ 




♦ 


Cayman Brae - females 




l^ 


f 


20 






'^ 


^ 




15 


A 


.^ 


k> 







40 



50 60 

snout-vent length (mm) 



70 



80 



0) 

n. 



0) 





A 


r 


40- 






30- 










r 






1 


20- 
























1 
















1 




n . 





















Little Cayman Little Cayman Cayman Brae Cayman Brae 
males females males females 





15 


o 
o 

• 


Little Cayman 
Little Cayman 
Cayman Brae 


males 

females 

males 






^ 


f 


E" 




♦ 


Cayman Brae 


females 




• 


:^W 




c 


10- 








^ 








CD 


9 
8 

7 


B 


o 


O 


o 









40 



50 60 

snout-vent length (mm) 



70 



80 



Figure 2. A, Differences in head dimensions be- 
tween both populations and sexes of Anolis maynardi. 
Whereas in both populations males (circles) have longer 
heads than females (diamonds), animals from Little 
Cayman (open symbols) are characterized by longer 
heads for their body size compared with animals from 
Cayman Brae (filled symbols). B, Differences in limb 
dimensions between populations and sexes. Whereas 
males have longer tibia than females, animals from the 
introduced population on Cayman Brae have longer 
tibia than animals from Little Cayman. 



Limb and body dimensions and sprint speed 

Islands (Wilks' lambda = 0.48; Fi5,47 = 
3.40; P = 0.001) and sexes (Wilks' lambda = 
0.53; F,5,47 = 2.73; P = 0.004) differed in 
limb dimensions, and the interaction between 
the two was also significant (Wilks' lambda 
= 0.61; F,5,47 = 2.04; P = 0.03). Males had 
longer hind-limb dimensions than females: 
(for all hind-limb segments: F| f,i > 1 1.00; all 



E 
o 



gi 

0) 



0) 

E 



gi 



400 



300 



200 



100 



B 


1 

















































































Little Cayman Little Cayman Cayman Brae Cayman Brae 
males females males females 

Figure 3. A, Differences in habitat use of Anolis 
maynardi. Animals on Cayman Brae use more open 
habitats characterized by greater distances to the nearest 
perch. B, Differences in sleep site use. Whereas in both 
populations males sleep higher than females, animals 
from the introduced population on Cayman Brae use 
higher vegetation than animals from Little Cayman. 



P < 0.01) radius length (Fi,6i = 6.12; P = 
0.02), the length of the longest toe on the 
forelimb (Fi,6i = 10.28; P = 0.002), and total 
forelimb length (Fi,6i = 11.34; P = 0.001). 
Animals from Cayman Brae had taller but 
narrower bodies and longer tibia and radii 
than animals from Little Cayman: body 
height (Fi,6i = 6.55; P = 0.01), body width 
(F,.6i = 4.32; P = 0.04), tibia length (F,,6i = 
8.44; P = 0.005), and radius length (F,,6i = 
5.03; P = 0.03) (Fig. 2; Table 1). Sex-by- 
population interaction effects were signifi- 
cant only for body height (Fi ^i = 5.23; P = 
0.03). Sprint speed was measured for animals 



2011 



ECOMORPHOLOGY OF A. MA YNARDI 



Table 2. Habitat use and sleep site characteristics for a native and an introduced population of 

AnOLIS ma YNARDI. 





Little Cayman 


Cayman Brae 




Male (« = 29)* 


Female (« = 24) 


Male (« = 29) 


Female (« = 32) 


Daytime perch height (cm) 


163 ± 118 


139 ± 87 


218 ± 95 


158 ± 75 


Daytime perch diameter (cm) 


4 ± 3 


6 ± 6 


8 ± 8 


9 ± 23 


Distance to nearest perch (cm) 


14 ± 10 


10 ± 5 


25 ± 22 


16 ± 10 


Diameter of nearest perch (cm) 


2 ± 2 


2±2 


4 ± 9 


3 ± 7 




« = 16 


« = 20 


« = 7 


« = 10 


Nighttime perch height (cm) 


214 ± 110 


153 ± 55 


258 ± 119 


171 ± 48 


Nighttime perch diameter (cm) 


5 ± 6 


9 ± 6 


1 ± 1 


8 ± 15 




« = 22 


« = 15 


« = 24 


« = 30 


Body temperature (°C) 


31.5 ± 1.7 


32.0 ± 1.4 


32.4 ± 2.0 


33.0 ± 1.8 


Air temperature (°C) 


29.2 ± 2.4 


30.5 ± 1.6 


29.8 ± 2.2 


30.5 ± 2.2 



*Table entries are means ± standard deviations. 



on Cayman Brae only and differs between 
the sexes (Fi,23 = 5.85; P = 0.02), with males 
being faster than females. 

Habitat use 

Populations (Wilks' lambda = 0.90; F4,96 
= 2.54; P = 0.045), but not sexes (Wilks' 
lambda = 1.08; F8,i92 = 1.08; P = 0.38), 
were different in habitat use. The interaction 
between population and sex was also not 
significant (Wilks' lambda = 0.95; F495 = 
1.28; P = 0.28). Populations differed in the 
distance to the nearest perch (Fi 99 = 8.27; P 
= 0.005), with animals from Cayman Brae 
being characterized by a greater distance to 
the nearest perch than animals from Little 
Cayman (Fig. 2, Table 2). Sexes (Wilks' 
lambda = 0.86; F2,6i = 4.92; P = 0.01) and 
populations (Wilks' lambda = 0.88; F2,6i = 
4.34; P = 0.02) also differed in their sleep 
sites. The interaction effect was, however, 
not significant (Wilks' lambda = 0.99; F2,6i 
= 0.43; P = 0.65). Differences between sexes 
and populations were significant for both 
perch height (sex: Fi,63 = 4.77; P = 0.03; 
population: F],63 = 4.79; P = 0.03) and 
perch diameter (sex: Fi 53 = 6.03; P = 0.02; 
population: Fj^s = 4.49; P = 0.04), with 



males sleeping higher but on narrower 
substrates than females and animals on little 
Cayman sleeping lower and on broader 
substrates than animals from Cayman Brae 
(Fig. 3; Table 2). 

Temperature 

Populations (Fi,85 = 5.47; P = 0.02) but 
not sexes (Fi,85 = 2.33; P = 0.13) differed 
significantly in body temperature, with ani- 
mals from Cayman Brae having higher body 
temperatures on average than animals from 
Little Cayman (Table 2). This difference 
was, however, not a consequence of variation 
in air temperature as no differences were 
observed in air temperature between popu- 
lations (F135 = 0.46; P = 0.50). 

DISCUSSION 

Anolis maynardi is a typical "green anole," 
as trunk-crown species are often called. 
Rarely found on the ground, it uses a wide 
variety of arboreal habitats (only 15% of the 
animals were observed at a height lower than 
1 m) — including trunks, narrow branches, 
twigs, and leaves — from eye level to the top 
of the canopy. Often locally abundant, the 



BREVIORA 



No. 522 



species is found everywhere where appropri- 
ate vegetation — primarily trees or human 
structures — occurs. 

Our surveys of animals on Little Cayman 
showed that they are relatively abundant and 
can be found throughout the island in a 
variety of vegetation types and habitats. 
However, animals were clearly most abundant 
in sea grape-dominated hemisclerophyllous 
evergreen shrubland along the southern edge 
of the island and in the relatively dense but low 
forest on the northern part of the island. Very 
few animals were observed in the mangroves. 
The wind-swept vegetation on the northeast 
coast of the island was also characterized by a 
lower abundance of individuals. On Cayman 
Brae animals were abundant in man-modified 
parkland near the airport and in the forested 
central part of the island. 

Differences between sexes 

Our data for both populations indicate a 
clear sexual dimorphism in body size, with 
males being larger than females (Grant 1940; 
Franz and Seidel, 1994). This has been 
observed for a closely related species, Anolis 
carolinensis (Irschick et al, 2005), and is 
characteristic for trunk-crown anoles in 
general (Butler et al., 2000). In addition to 
being dimorphic in body size, male A. 
maynardi also have relatively longer heads 
and snouts (Franz and Seidel, 1994) and 
have relatively longer hind limbs than 
females, patterns that are also exhibited by 
A. carolinensis (Irschick et al, 2005). The 
wider and overall larger heads of males give 
them a performance advantage and conse- 
quently males have greater relative bite 
forces than females (Table 1). Finally, our 
data suggest that at least for the animals 
from Cayman Brae, males also have higher 
sprint speeds than females, which may be 
related to the intersexual difference in limb 
length (Macrini and Irschick, 1998). 



Differences between populations 

Lizards on the two islands differed in 
ecology, morphology, and performance. For 
example, individuals from Little Cayman 
have longer heads and snouts and lower bite 
forces. Although it remains unclear why 
individuals on Little Cayman have relatively 
lower bite forces despite their relatively wider 
heads, we suggest that subtle shape differ- 
ences in the adductor chamber (e.g., see 
Herrel et al., 2007) may lie at the base of this 
result. Beyond differences in head size and 
shape, our data suggest that animals from 
the introduced population on Cayman Brae 
also have relatively longer limbs. This 
accords well with the use of generally (but 
not significantly so) wider perches on Cay- 
man Brae (Table 2), which is known to be 
correlated to the evolution of greater limb 
lengths in Greater Antillean anoles (Losos, 
2009). The use of wider perches is reflective 
of the overall habitat structure on Cayman 
Brae, which is characterized by a more open, 
less densely forested habitat with larger and 
taller trees. Indeed, Cayman Brae's tilted, 
elevated plateau (where we caught the 
majority of the Uzards included in our 
sample) is dominated by xeromorphic semi- 
deciduous forest. This is reflected in the 
significantly greater distance to nearest perch 
for animals on Cayman Brae compared with 
Little Cayman. As a result of the more open 
habitat structure on Cayman Brae, animals 
on that island are more exposed with less 
cover, which may explain why Cayman Brae 
lizards had higher body temperatures on 
average (but note that air temperatures did 
not differ between Cayman Brae and Little 
Cayman). However, our visit to Cayman 
Brae came only 5 months after the island was 
severely affected by Hurricane Paloma in 
November 2008. Paloma stripped the foliage 
off many trees and felled many others, 
opening up the canopy (God beer et al. 



2011 



ECOMORPHOLOGY OF A. MA YNARDI 



2008). Consequently, the differences in hab- 
itat structure and attendant lizard ecology 
may have been a result of these differences 
and possibly may disappear as the vegetation 
on Cayman Brae recovers. 

The morphological differences between A. 
maynardi on Little Cayman and Cayman Brae 
could have three explanations. First, the 
differences may represent rapid evolutionary 
adaptation to different environmental condi- 
tions experienced by the introduced popula- 
tion. Alternatively, second, the differences 
may represent phenotypic plasticity; anoles 
growing in different environments may devel- 
op different phenotypic characteristics. Al- 
though plasticity has not been much studied 
in anoles, laboratory experiments have shown 
that A. carolinensis and Anolis sagrei both 
develop longer hind limbs if they are raised on 
broader surfaces (Losos et al, 2000; Kolbe 
and Losos, 2005). Finally, third, the Cayman 
Brae population may not have changed at all, 
but rather may be derived from a population 
on Little Cayman that we did not sample. If 
this is the case, it would indicate an interesting 
extent of geographic variation on a relatively 
small island like Little Cayman. 

Much still remains to be learned about the 
biology of this little-known but fascinating 
species. The adaptive significance, if any, of 
the extraordinarily elongated snout of males 
of the species is unclear. Biomechanics of jaw 
movement suggest that long jaws would give 
an individual a performance advantage in 
capturing mobile, flying prey items (Herrel et 
al., 2007). Why this trait is so dimorphic also 
requires explanation; sexual selection is one 
obvious possibility, with long snouts poten- 
tially benefitting males during male-male 
contests involving jaw locking. In addition, 
the impact of the introduction of A. may- 
nardi on the native fauna of Cayman Brae 
also merits investigation, as well as the extent 
to which this species may be adapting to 
local conditions. 



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