Hormones, sexual signals, and performance of green anole lizards (Anolis carolinensis)

The evolutionary processes that result in reliable links between male signals and fighting capacity have received a great deal of attention, but the proximate mechanisms underlying such connections remain understudied. We studied a large sample of male green anole lizards (Anolis carolinensis) to determine whether testosterone or corticosterone predicted dewlap size and/or bite-force capacity, as dewlap size is known to be a reliable predictor of bite-force capacity in territorial males. We also examined whether these relationships were consistent between previously described body size classes ("lightweights" and "heavyweights"). Heavyweights had 50% higher testosterone concentrations than lightweights during the breeding season, suggesting a mechanism for the disproportionately larger heads and dewlaps and higher bite-forces of heavyweights. Plasma testosterone concentrations were positively correlated with dewlap size and bite-force performance in lightweights (but not heavyweights) but only because of mutual intercorrelation of all three variables with body size. We suggest two possibilities for the relationship between testosterone levels and body size: (1) testosterone promotes growth in this species or (2) smaller sexually mature males are unable to compete with larger males such that the benefits of elevated testosterone do not outweigh the costs. Corticosterone levels did not differ between the male morphs, and lightweights, but not heavyweights, showed an inverse relationship between testosterone levels and corticosterone levels. Our results suggest that testosterone is important for traits related to dominance in adult male green anoles and may influence the ability to compete with rivals via fighting ability or through the use of signals.     

Intraspecific correlations among morphology, performance and habitat use within a green anole lizard (Anolis carolinensis) population

We examined habitat use, morphology, jumping and clinging ability for 403 juvenile, female and male green anole lizards, Anolis carolinensis, in a population in south‐eastern Louisiana. We sought to answer three questions: (1) Do age/sex classes differ in habitat use, morphology and performance ability? (2) Do habitat use, morphology and performance correlate among all individuals across three age/sex classes (juveniles, females and males)? (3) Do juveniles compensate for their poor absolute performance capacities by being better performers on a relative scale? The three age/sex classes were found to differ significantly in size‐adjusted morphology, habitat use and size‐adjusted performance capacity. Juveniles tended to occupy perches which were closer together than those of adult males and females. The distal elements of the hindlimb (femur, tibia) were significantly longer in males than in females and juveniles, while females were more stocky than males and juveniles. The only significant overall ecomorphological relationship detected was between the lengths of the distal hindlimb elements and maximum jump acceleration. Our hypothesis that juveniles should be better performers (relative to size) compared to adults was disproved, as adult females were always the best performers relative to size. Our analysis of a mainland anole population presents a different view of population structure compared to similar studies involving Caribbean Anolis lizards, which show more ecological differentiation among age/sex classes, and also show that juveniles are relatively good performers. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 211–221.     

A comparison of habitat use, morphology, clinging performance and escape behaviour among two divergent green anole lizard (Anolis carolinensis) populations

We measured available and actual habitat use, morphology, escape behaviour and clinging ability in a large sample ( N  = 242) of green anoles, Anolis carolinensis , in a habitat consisting primarily of segregated dense clumps of broad leaves, Aspidistra elatior (Tulane University campus, LA) to compare against similar data collected previously from a more typical habitat c. 30 km away, consisting of continuous strands of bushes and trees (Good Hope Field, St. Charles Parish, LA). At Tulane the anoles perched primarily on the broad, smooth leaves of broad leaves, whereas in Good Hope Field (GHF) they predominantly perched on branches and tree trunks. The two populations differed significantly in morphology. In Tulane, the anoles tended to have shorter distal hindlimb elements, longer forelimb elements, and were more 'slender' than those at GHF. A comparison of escape behaviour showed population and sex differences. In both populations, females had significantly longer approach distances (i.e. were more 'wary') than males. These distances were, in addition, significantly longer at GHF than at Tulane for both sexes; this may be due to the potentially higher diversity and abundance of predators at GHF, although habituation to humans may also play a role. Anoles at Tulane had significantly larger toepads and higher clinging abilities than those at GHF. The enhanced clinging abilities of anoles at Tulane may have arisen due to their propensity to use smooth leaves as their primary substrate. Overall, our data reveal substantial ecological, behavioural, morphological, and functional differences among populations, some of which may be adaptive.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 223–234.     

Development of microsatellite markers in the St Lucia anole, Anolis luciae

Anolis lizards are important models in studies of ecology and evolution. Here we describe 13 polymorphic microsatellites for use in population screening in the St Lucia anole, Anolis luciae, that can be used as a natural replicate to Anolis roquet on Martinique to study processes involved in population differentiation and speciation. Genotyping of 32 individuals using M13 tails and FAM-labelled universal M13 primers showed that all loci were polymorphic with high genetic diversity, averaging at 16.8 alleles per locus. Genotypic frequencies conformed to Hardy-Weinberg expectations, and there were no instances of linkage disequilibrium between loci.     

Morphological variation in the tropical anole, Anolis casildae (Squamata: Polychrotidae)

We describe morphological variation (scalation and coloration) observed among eight individuals of the Panamanian lizard species Anolis casildae. This variation was not observed in the holotype and aids in identification of this recently described species (originally described on the basis of a single, male specimen). This species occurs only in the Reserva Forestal Fortuna (Chiriquí Province) and the adjacent Bosque Protector Palo Seco (Bocas del Toro Province) in western Panama. Anolis casildae can be distinguished from all other Panamanian anole species via six features: (1) two enlarged superciliary scales (the first larger than the second); (2) an anterior nasal scale in contact with the rostral scale or separated from the rostral by one scale; (3) 6-8 sublabial scales to the center of the eye; (4) 3-4 scales between the supraobital semicircles; (5) unique coloration (4-6 oblique brown bands interspersed by blue-outlined yellow patches; dewlap is a dirty cream color with broad yellow scale rows irregularly interspersed with smaller emerald green scales) and (6) A. casildae occurs from 1,050 to 1,400 m in the Cordillera Central. We also compare our natural history observations of A. casildae to a similar large anole, A. frenatus, a species which we believe A. casildae to be closely related.     

Habitat light, colour variation, and ultraviolet reflectance in the Grand Cayman anole, Anolis conspersus

Data from a diversity of sources are consistent with the hypothesis that the Grand Cayman anole, Anolis conspersus, is descended directly from Anolis grahami of Jamaica. Although the two species have remained morphologically similar, coloration in A. conspersus has changed considerably from that of its ancestor. The most dramatic difference is seen in dewlap colour, where A. conspersus has evolved a blue and highly UV-reflective dewlap from the ancestral orange-and-yellow colour state. In addition, variation in normal (non-metachrosis) dorsum coloration in A. grahami populations is limited to shades of green (olive, emerald, teal), whereas in A. conspersus dorsum coloration varies from green to blue and to brown. This increased colour variation occurs despite Grand Cayman being a small, relatively featureless island only 35 km in length. Results of this study suggest that ambient light differences associated with precipitation-related vegetation structure may have played an important role in the evolution of A. conspersus body colour variation. Evidence is presented to show how geological, ecological, and physiological factors could have interacted to select for a short wavelength-reflective dewlap from a long wavelength-reflective precursor following the colonization of Grand Cayman from Jamaica by A. grahami between 2 and 3 Mya.     

Factors restricting the range expansion of the invasive green anole Anolis carolinensis on Okinawa Island,Japan

The green anole Anolis carolinensis invaded the Ogasawara Islands in Japan, drove various native species to extinction, and its distribution expanded 14 years after initial establishment. A. carolinensis invaded Okinawa Island, but it has not expanded its distribution in more than 25 years, although its density is extremely high in the southern region. To determine whether A. carolinensis has the potential to expand its distribution on Okinawa Island, we performed phylogenetic analysis of mitochondrial ND2 DNA sequences to study the origin of A. carolinensis that invaded Okinawa Island. We further used a species distribution model (MaxEnt) based on the distribution of native populations in North America to identify ecologically suitable areas on Okinawa Island. Nucleotide sequence analysis shows that the invader A. carolinensis originated in the western part of the Gulf Coast and inland areas of the United States and that a portion of the anoles on Okinawa was not introduced via the Ogasawara Islands. The MaxEnt predictions indicate that most areas in Okinawa Island are suitable for A. carolinensis. Therefore, A. carolinensis may have the potential to expand its distribution in Okinawa Island. The predictions indicate that habitat suitability is high in areas of high annual mean temperature and urbanized areas. The values of precipitation in summer in the northern region of Okinawa Island were higher compared with those of North America, which reduced the habitat suitability in Okinawa Island. Adaptation to low temperatures, an increase in the mean temperature through global warming, and an increase in open environments through land development will likely expand the distribution of A. carolinensis in Okinawa Island. Therefore, we must continue to monitor the introduced populations and be alert to the possibility that city planning that increases open environments may cause their range to expand.     

Assessment of the mass,length, center of mass,and principal moment of inertia of body segments in adult males of the brown anole (Anolis sagrei) and green,or carolina,anole (Anolis carolinensis)

This study provides a morphometric data set of body segments that are biomechanically relevant for locomotion in two ecomorphs of adult male anoles, namely, the trunk‐ground Anolis sagrei and the trunk‐crown Anolis carolinensis. For each species, 10 segments were characterized, and for each segment, length, mass, location of the center of mass, and radius of gyration were measured or calculated, respectively. The radii of gyration were computed from the moments of inertia by using the double swing pendulum method. The trunk‐ground A. sagrei has relatively longer and stockier hindlimbs and forelimbs with smaller body than A. carolinensis. These differences between the two ecomorphs demonstrated a clear relationship between morphology and performance, particularly in the context of predator avoidance behavior, such as running or jumping in A. sagrei and crypsis in A. carolinensis. Our results provide new perspectives on the mechanism of adaptive radiation as the limbs of the two species appear to scale via linear factors and, therefore, may also provide explanations for the mechanism of evolutionary changes of structures within an ecological context. J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.     

Transport of helminths to Hawaii via the brown anole, Anolis sagrei (Polychrotidae)

Sixty-two brown anoles, Anolis sagrei, from Oahu, Hawaii were examined for helminths. Anolis sagrei was introduced to Hawaii, presumably from the Caribbean. Two species of trematodes, Mesocoelium monas and Platynosomum fastosum, 3 species of nematodes, Atractis scelopori, Physaloptera squamatae, and Physocephalus sp., 1 acanthocephalan, Acanthocephalus bufonis, and 1 pentastome, Raillietiellafrenatus, were found. Atractis scelopori and P. squamatae, previously unknown in Hawaii, are widely distributed in the Caribbean and were most likely transported to Hawaii with the introduced anoles. Mesocoelium monas, P. fastosum, Physocephalus sp., A. bufonis, and R. frenatus have been previously reported from Hawaiian herptiles; A. sagrei most likely acquired infections of these parasites from Hawaiian populations. This study indicates that helminths can be transported with their introduced hosts and become established in the colonized areas and that introduced lizards may quickly acquire species of previously established helminthes.     

Effect of locomotor approach on feeding kinematics in the green anole (Anolis carolinensis)

Squamates are well-known models for studying to examine locomotor and feeding behaviors in tetrapods, but studies that integrate both behavioral activities remain scarce. Anolis lizards are a classical lineage to study the evolutionary relationships between locomotor behavior and complex structural features of the habitat. Here, we analyzed prey-capture behavior in one representative arboreal predator, Anolis carolinensis, to demonstrate the functional links between locomotor strategies and the kinematics of feeding. A. carolinensis uses two strategies to catch living insects on perches: Head-Up Capture and Jump Capture. In both cases, lizards use lingual prehension to capture the prey and the kinematic patterns of the trophic apparatus are not significantly influenced by the selected strategies. Therefore, to capture one prey type, movements of the trophic structures are highly fixed and A. carolinensis modulates the locomotor pattern to exploit the environment. Predation behavior in A. carolinensis integrates two different behavioral patterns: locomotor plasticity of prey-approach and biomechanical stereotypy of tongue prehension to successfully capture the prey.     

Habitat use and ecological interactions of an introduced and a native species of Anolis lizard on Grand Cayman,with a review of the outcomes of anole introductions

Since its introduction ten years ago, Anolis sagrei has spread over much of Grand Cayman and is now more common in some habitats than the native anole, A. conspersus. Interspecific differences in body size, perch height, and microclimatic preference may have facilitated the colonization. Nonetheless, competition may be occurring between the species; comparisons with studies of habitat use prior to the arrival of A. sagrei indicate that in open habitats, where A. sagrei is now abundant, A. conspersus perches higher, but in closed habitats, where A. sagrei is absent, no change in perch height is evident. Review of data concerning 23 Anolis introductions indicates that the presence or absence of an ecologically similar native species may be an important determinant of colonization success or failure.     

The incredible shrinking dewlap: signal size,skin elasticity,and mechanical design in the green anole lizard (Anolis carolinensis)

The expression of male secondary sexual traits can be dynamic, changing size, shape, color, or structure over the course of different seasons. However, the factors underlying such changes are poorly understood. In male Anolis carolinensis lizards, a morphological secondary sexual signal called the dewlap changes size seasonally within individuals. Here, we test the hypothesis that seasonal changes in male dewlap size are driven by increased use and extension of the dewlap in spring and summer, when males are breeding, relative to the winter and fall. We captured male green anole lizards prior to the onset of breeding and constrained the dewlap in half of them such that it could not be extended. We then measured dewlap area in the spring, summer, and winter, and dewlap skin and belly skin elasticity in summer and winter. Dewlaps in unconstrained males increase in area from spring to summer and then shrink in the winter, whereas the dewlaps of constrained males consistently shrink from spring to winter. Dewlap skin is significantly more elastic than belly skin, and skin overall is more elastic in the summer relative to winter. These results show that seasonal changes in dewlap size are a function of skin elasticity and display frequency, and suggest that the mechanical properties of signaling structures can have important implications for signal evolution and design.     

Evolutionary correlations among morphology, habitat use and clinging performance in Caribbean Anolis lizards

A central issue in evolutionary biology concerns whether morphology, performance and habitat use have coevolved. We investigated evolutionary relationships among the size of the subdigital toepad, clinging ability and perch height in 12 species of Caribbean Anolis lizard. Specifically, we predicted that: (1) because larger anole species tend to perch high in the canopy, both toepad area and clinging ability should scale with positive allometry to enable small and large lizards to possess approximately similar ratios of both variables relative to mass; (2) anole species with relatively larger toepads (i.e. size-adjusted) should be relatively better clingers compared with species with relatively small toepads; (3) species that perch high in the canopy should possess relatively large clinging abilities (either on an absolute or a size-adjusted basis). Our first hypothesis was refuted, as both toepad area and clinging ability scaled close to isometry (0.67) relative to mass, indicating that large lizard species have low ratios of clinging ability to mass compared with small lizard species. However, our second and third predictions were confirmed. Anole species with relatively larger toepads were relatively better clingers compared with species with relatively smaller toepads. Anole species that perched high in the canopy (either on an absolute scale or relative to size) tended to have relatively larger toepads and greater clinging capacities compared with species that perched lower in the canopy. These data provide indirect comparative evidence that the evolution of increased toepad size in some anole species is adaptive, by facilitating the occupation of perches high in the canopy.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 389–398.     

Both sexes suffer increased parasitism and reduced energy storage as costs of reproduction in the brown anole,Anolis sagrei

Sexual selection theory proposes that males suffer reduced immune function and increased parasitism as costs of expressing sexual signals. Life‐history theory proposes that females suffer the same costs because of inherent trade‐offs between reproduction and self‐maintenance. Mechanistically, each theory invokes an energetic trade‐off, although few experiments have directly compared these costs of reproduction between the sexes as a result of fundamental sex differences in the nature of reproductive investment and a tendency for each theory to focus on a single sex. To test whether males and females experience comparable costs of reproduction in terms of energetics, immune function, and parasitism, we used gonadectomy to eliminate most aspects of reproductive investment in wild brown anole lizards (Anolis sagrei) of both sexes. We compared these nonreproductive males and females with intact, reproductive controls with respect to stored energy (fat bodies), immune function (swelling response to phytohemagglutinin), and the prevalence and intensity of infection by four types of parasite (gastric nematodes, intestinal nematodes, faecal coccidia, and ectoparasitic mites). Gonadectomized anoles experienced dramatic increases in fat storage that were accompanied by decreases in the prevalence of intestinal nematodes and in the intensity of coccidia infection. These costs of reproduction were comparable between males and females, although neither sex exhibited the predicted increase in immune function after gonadectomy. Our results suggest that, despite fundamental sex differences in the nature of reproductive investment, both male and female anoles experience similar costs of reproduction with respect to energy storage and some aspects of parasitism.     

Performance capacity, fighting tactics and the evolution of life-stage male morphs in the green anole lizard (Anolis carolinensis)

The evolution of alternative male phenotypes is probably driven by male-male competition for access to reproductive females, but few studies have examined whether whole-organism performance capacities differ between male morphs, and if so whether any such differences affect fighting ability. We show how ontogenetic changes in performance and morphology have given rise to two distinct life-stage male morphs exhibiting different fighting tactics within the green anole lizard (Anolis carolinensis). Field studies show a bimodal distribution of adult males within a single population: larger 'heavyweight' males have relatively large heads and high bite forces for their size, whereas smaller 'lightweight' males have smaller heads and lower bite forces. In staged fights between size-matched heavyweight males, males with greater biting ability won more frequently, whereas in lightweight fights, males with greater jumping velocity and acceleration won more often. Because growth in reptiles is indeterminate, and the anole males examined are sexually mature, we propose that the heavyweight morph arose through selection against males with small heads and poor bite forces at the lightweight-heavyweight size transition. Our findings imply that one may not be able to predict male fighting success (and hence potential mating success) by examining aspects of male 'quality' at only one life stage.     

Microhabitat use and diet of 0+ cyprinid fishes in a lentic, regulated reach of the River Great Ouse, England

In the River Great Ouse, 0+ roach, bream, chub, bleak and gudgeon were each divided into three' ecospecies' on the basis of their morphology: young larvae, old larvae and juveniles. Ecologically similar species were positively associated and dissimilar species were negatively associated. All ecospecies, except juvenile bleak preferred water < 1 m deep, within 6 m of the bank with some plant cover. Habitat use was similar for all species. It is suggested that this habitat offers increased growth rate, reduced predation risk and increased food abundance to all species, and that species overlap is due to complementary habitat use rather than aggregation. During the early larval period all species fed predominantly upon rotifers and diatoms. During the late larval period there was a switch to Cladocera, primarily Chydoridae and Ceriodaphnia sp., and chironomid larvae. Species-specific dietary selection was evident during the juvenile period, with roach feeding primarily upon aufwuchs, bream upon Cladocera, chub upon Diptera, and gudgeon upon Copepoda.