Anolis Sagrei Research Articles

ECOLOGICAL RELEASE ANALYZED AMONG INDIVIDUALS, ACROSS TWO GENERATIONS, AND ALONG MULTIPLE NICHE AXES IN ANOLIS CAROLINENSIS

A population freed from a constraining interspecific interaction (e.g., competition or predation) may experience niche shifts and expansions. This phenomenon, termed ecological release, is an eco-evolutionary process driven by individual behaviors and interindividual interactions. However, empirical studies of these interactions seldom observe them directly, instead inferring process from pattern. Here, we set up experimental conditions for ecological release of the lizard Anolis carolinensis (green anole) from constraining interactions with its congener, Anolis sagrei (brown anole), by constituting populations of lizards on small islands. We monitored individual and population habitat use along three niche axes (perch height, perch diameter, and lateral movement between perches) on one experimental (one-species) and one control (two-species) island, for three time periods: 1) preremoval, when both islands had both species; 2) postremoval, shortly after A. sagrei were cleared from the experimental island; and 3) delayed postremoval, 7 months later, when long-lived lizards were joined by a second generation born in the intervening months. We found that green anole perch height decreased on the one-species island and increased on the two-species island. These shifts did not occur during postremoval but were evident by delayed postremoval, when both generations on the one-species island were perching nearly 130 cm lower than their counterparts on the two-species island. We also documented correlated changes in perch diameter at both the individual and population level but no changes in the extent of individuals' lateral movement. Lastly, changes in population-level niche width (i.e., perch height and diameter variances) occurred without detectable changes in niche overlap among individuals. Our results demonstrate that that the dynamics of ecological release in nature need not be inferred, because experiments can observe them directly in individuals, across generations, and along multiple niche axes.

Propagule size and sex ratio influence colonisation dynamics after introduction of a non-native lizard.

The composition of founding populations plays an important role in colonisation dynamics and can influence population growth during early stages of biological invasion. Specifically, founding populations with small propagules (i.e. low number of founders) are vulnerable to the Allee effect and have reduced likelihood of establishment compared to those with large propagules. The founding sex ratio can also impact establishment via its influence on mating success and offspring production. Our goal was to test the effects of propagule size and sex ratio on offspring production and annual population growth following introductions of a non-native lizard species (Anolis sagrei). We manipulated propagule composition on nine small islands, then examined offspring production, population growth and survival rate of founders and their descendants encompassing three generations. By the third reproductive season, per capita offspring production was higher on islands seeded with a relatively large propagule size, but population growth was not associated with propagule size. Propagule sex ratio did not affect offspring production, but populations with a female-biased propagule had positive growth, whereas those with a male-biased propagule had negative growth in the first year. Populations were not affected by propagule sex ratio in subsequent years, possibly due to rapid shifts towards balanced (or slightly female biased) population sex ratios. Overall, we show that different components of population fitness have different responses to propagule size and sex ratio in ways that could affect early stages of biological invasion. Despite these effects, the short life span and high fecundity of A. sagrei likely helped small populations to overcome Allee effects and enabled all populations to successfully establish. Our rare experimental manipulation of propagule size and sex ratio can inform predictions of colonisation dynamics in response to different compositions of founding populations, which is critical in the context of population ecology and invasion dynamics.

A summary of reports of the Cuban Brown Anole (Anolis sagrei) in Texas, USA

A summary of reports of the Cuban Brown Anole (Anolis sagrei) in Texas, USA

Male-male aggression in the introduced Cuban Brown Anole, Norops sagrei (Reptilia: Dactyloidae), in Honduras

Male-male aggression in the introduced Cuban Brown Anole, Norops sagrei (Reptilia: Dactyloidae), in Honduras

First report of the Southern Gulf Coast Toad (Incilius valliceps Wiegmann), Common House Gecko (Hemidactylus frenatus Duméril and Bibron), Schmidt’s Black-Striped Snake (Coniophanes schmidti Bailey), and Cozumel Whiptail (Aspidoscelis cozumela Gadow), on Turneffe Atoll, Belize

Each year from 2012 to 2019, during a 12-day period in November or December, we photographed common herpetofauna on Calabash Caye, a small mangrove-dominated island on the eastern edge of Turneffe Atoll, Belize. Turneffe Atoll is home to the newest, largest, and most biodiverse marine protected area in Belize. Calabash Caye exemplifies the islands on Turneffe’s eastern edge whose elevated beach ridges enable the development of coastal strand plain and littoral forest habitats, which are among the most threatened habitats in the world. As no herpetofaunal survey has been published for Turneffe in over twenty years, and as the herpetofauna is a conspicuous indicator of the health of terrestrial ecological communities on islands, we leveraged our annual field excursions to Calabash Caye to compile a photographic record of the island’s reptiles and amphibians. In multiple years, we documented the presence of five lizards (Anolis sagrei mayensis, Aspidoscelis cozumela, Ctenosaura similis, Phyllodactylus tuberculosus, and the invasive species Hemidactylus frenatus), three snakes (Boa imperator, Leptophis mexicanus hoeversi, and Coniophanes schmidti), and one amphibian (Incilius valliceps). This represents the first report of A. cozumela, H. frenatus, C. schmidti, and I. valliceps on Calabash Caye or on any island in Turneffe Atoll; H. frenatus, C. schmidti, and I. valliceps have never been reported on any of the Belizean cayes. We did not observe four species that have previously been reported on Calabash Caye: Brown Basilisk (Basiliscus vittatus), Mesoamerican Cane Toad (Rhinella horribilis), Mayan Skink (Marisora lineola; formerly Mabuya unimarginata), or a blindsnake, provisionally identified as Indotyphlops braminus. We also include photos of Anolis allisoni, Ctenosaura similis, and Anolis sagrei mayensis obtained during four single-day excursions to Half Moon Caye on Lighthouse Atoll; this represents three of four species reported from that location during the 1990s.

Environmental Thermal Stress Induces Neuronal Cell Death and Developmental Malformations in Reptiles.

SynopsisEvery stage of organismal life history is being challenged by global warming. Many species are already experiencing temperatures approaching their physiological limits; this is particularly true for ectothermic species, such as lizards. Embryos are markedly sensitive to thermal insult. Here, we demonstrate that temperatures currently experienced in natural nesting areas can modify gene expression levels and induce neural and craniofacial malformations in embryos of the lizard Anolis sagrei. Developmental abnormalities ranged from minor changes in facial structure to significant disruption of anterior face and forebrain. The first several days of postoviposition development are particularly sensitive to this thermal insult. These results raise new concern over the viability of ectothermic species under contemporary climate change. Herein, we propose and test a novel developmental hypothesis that describes the cellular and developmental origins of those malformations: cell death in the developing forebrain and abnormal facial induction due to disrupted Hedgehog signaling. Based on similarities in the embryonic response to thermal stress among distantly related species, we propose that this developmental hypothesis represents a common embryonic response to thermal insult among amniote embryos. Our results emphasize the importance of adopting a broad, multidisciplinary approach that includes both lab and field perspectives when trying to understand the future impacts of anthropogenic change on animal development.

Predation of Cuban Brown Anoles, Anolis sagrei (Squamata: Dactyloidae), by House Sparrows, Passer domesticus (Aves: Passeriformes), and an annotated list of lizards preyed upon by House Sparrows

Predation of Cuban Brown Anoles, Anolis sagrei (Squamata: Dactyloidae), by House Sparrows, Passer domesticus (Aves: Passeriformes), and an annotated list of lizards preyed upon by House Sparrows

Impacts of an invasive species (Anolis sagrei) on social and spatial behaviours of a native congener (Anolis carolinensis)

Interspecific aggression has important fitness consequences across the animal kingdom and can be especially important during species invasions, where asymmetric interactions between native and invasive species can lead to native species declines. We investigated the immediate behavioural consequences of interspecific interactions for a native species, the green anole lizard, Anolis carolinensis , after an invasion by a closely related invasive species, the Cuban brown anole, Anolis sagrei . We housed captive populations of green anoles (6 males, 6 females) in large outdoor enclosures and recorded their display behaviours (displays/min), activity levels (movements/min) and habitat use (2D and 3D home range size, perch height) for 10 days. We then introduced brown anoles and recorded the green anoles' behaviours for another 10 days, seeking differences between pre- and post-invasion behaviours. We recorded behavioural interactions between individuals (i.e. headbob and dewlap displays, chases, mating attempts, fights and copulations) throughout the study. To serve as a density control, we duplicated the experiment in a second enclosure using green anoles as ‘invaders’. We performed the experiment eight times with two densities of invaders: high (4 males, 4 females) and low (2 males, 2 females). We found that green anoles have smaller two-dimensional and three-dimensional home ranges and higher average perch heights after invasions but that these changes resulted from increased population densities rather than aggression from brown anole invaders. Furthermore, although green and brown anoles did display to each other, both species preferentially interacted with conspecifics and escalated aggressive behaviours between the two species (e.g. lock-jawed fights) rarely occurred. Taken together, these findings indicate that high brown anole population densities, rather than direct interference competition, could be driving green anole displacement across the brown anole's invasive range. • Invasive brown anoles are thought to be aggressive towards native green anoles. • We ‘invaded’ captive populations of green anoles with brown anoles. • Changes in green anole behaviours after invasions were linked to invader density. • Green and brown anoles engaged in few escalated aggressive interactions. • High brown anole densities, not aggression, may be driving green anole declines.

First Report on Detection and Molecular Characterization of Adenoviruses in the Small Indian Mongoose (Urva auropunctata).

Using a broad-range nested PCR assay targeting the DNA-dependent DNA polymerase (pol) gene, we detected adenoviruses in 17 (20.48%) out of 83 fecal samples from small Indian mongooses (Urva auropunctata) on the Caribbean island of St. Kitts. All 17 PCR amplicons were sequenced for the partial pol gene (~300 bp, hereafter referred to as Mon sequences). Fourteen of the 17 Mon sequences shared maximum homology (98.3–99.6% and 97–98.9% nucleotide (nt) and deduced amino acid (aa) sequence identities, respectively) with that of bovine adenovirus-6 (species Bovine atadenovirus E). Mongoose-associated adenovirus Mon-39 was most closely related (absolute nt and deduced aa identities) to an atadenovirus from a tropical screech owl. Mon-66 shared maximum nt and deduced aa identities of 69% and 71.4% with those of atadenoviruses from a spur-thighed tortoise and a brown anole lizard, respectively. Phylogenetically, Mon-39 and Mon-66 clustered within clades that were predominated by atadenoviruses from reptiles, indicating a reptilian origin of these viruses. Only a single mongoose-associated adenovirus, Mon-34, was related to the genus Mastadenovirus. However, phylogenetically, Mon-34 formed an isolated branch, distinct from other mastadenoviruses. Since the fecal samples were collected from apparently healthy mongooses, we could not determine whether the mongoose-associated adenoviruses infected the host. On the other hand, the phylogenetic clustering patterns of the mongoose-associated atadenoviruses pointed more towards a dietary origin of these viruses. Although the present study was based on partial pol sequences (~90 aa), sequence identities and phylogenetic analysis suggested that Mon-34, Mon-39, and Mon-66 might represent novel adenoviruses. To our knowledge, this is the first report on the detection and molecular characterization of adenoviruses from the mongoose.

Niche lability mitigates the impact of invasion but not urbanization.

Native species can coexist with invasive congeners by partitioning niche space; however, impacts from invasive species often occur alongside other disturbances. Native species' responses to the interactions of multiple disturbances remain poorly understood. Here we study the impacts of urbanization and an invasive congener on a native species. Using abundance (catch-per-unit effort) and vertical distribution of native green anoles (Anolis carolinensis) and invasive brown anoles (Anolis sagrei) across a gradient of natural-to-urban forests, we ask if niche shifting (lability) is occurring, and if it can mitigate impacts from one or both disturbances. We use generalized linear models to relate species abundances across the landscape to urbanization, forest structural complexity, and congener abundances (i.e., A. sagrei); and test for an interaction between urbanization and congener abundance. Our data show that A. sagrei presence results in a 17-fold upward shift in vertical niche of A. carolinensis-an 8.3m shift in median perch height, and models reveal urbanization also drives an increase in A. carolinensis perch height. A. carolinensis and A. sagrei abundances negatively and positively correlate with urbanization, respectively, and neither species' abundance correlate with congener abundance. Despite a positive correlation between A. sagrei abundance and urbanization, our results do not show evidence of this interaction affecting A. carolinensis. Instead, niche lability appears to enable the native species to mitigate the impact of one driver of decline (invasive competition) while our data suggest it declines with the second (urbanization).

Spatial and temporal variation in phenotypes and fitness in response to developmental thermal environments

AbstractPhenotypic variation within populations is influenced by the environment via plasticity and natural selection. How phenotypes respond to the environment can vary among traits, populations and life stages in ways that can influence fitness.Plastic responses during early development are particularly important because they can affect components of fitness throughout an individual's life. Consequently, how natural selection shapes developmental plasticity could be influenced by fitness consequences across different life stages. Moreover, spatial variation in selection pressures could generate differences in plastic responses among populations.To gain insight into sources of variation in phenotypes and survival, we used a laboratory egg incubation experiment using brown anole lizardsAnolis sagreifrom mainland (ancestral) and island (descendent) populations, combined with a mark–release–recapture experiment in the field. Our study was designed to (a) quantify the effects developmental temperature on embryo development and offspring morphology, (b) assess how developmental temperature influences offspring survival across different life stages and (c) quantify how thermal reaction norms vary among ancestral and descendant populations.Developmental temperature influenced offspring morphology, but thermal reaction norms of embryos showed little variation among populations. Developmental temperature influenced offspring survival, but the patterns differed between embryo and hatchling stages; the optimal temperature for embryos was about 5℃ lower than that for hatchlings. High temperatures were thermally stressful to embryos, but they reduced incubation duration and led to early hatching. In turn, earlier hatching increased the probability of survival to adulthood. Moreover, the effect of developmental temperature on hatchling survival was most pronounced for offspring that hatched late in the season.The difference in optimal developmental temperatures between life stages may be driven by physiological tolerance for embryos and by ecological factors for hatchlings. Moreover, the fitness consequences of the developmental environment depend on the phenology of hatching. Overall, these results highlight how the developmental environment can differentially affect fitness across life stages and show that temporal thermal heterogeneity can influence survival of embryos, but the consequences on post‐hatching stages may vary at different times of the season.A freePlain Language Summarycan be found within the Supporting Information of this article.

Reproductive trade-offs and phenotypic selection change with body condition, but not with predation regime, across island lizard populations.

Trade-offs between reproduction and survival are central to life-history theory and are expected to shape patterns of phenotypic selection, but the ecological factors structuring these trade-offs and resultant patterns of selection are generally unknown. We manipulated reproductive investment and predation regime in island populations of brown anole lizards (Anolis sagrei) to test (1) whether previously documented increases in the survival of experimentally non-reproductive females (OVX=ovariectomy) reflect the greater susceptibility of reproductive females (SHAM=control) to predation and (2) whether phenotypic selection differs as a function of reproductive investment and predation regime. OVX females exceeded SHAM controls in growth, mass gain and body condition, indicating pronounced energetic costs of reproduction. Although mortality was greatest in the presence of bird and snake predators, differences in survival between OVX and SHAM were unrelated to predation regime, as were patterns of natural selection on body size. Instead, we found that body condition at the conclusion of the experiment differed significantly across populations, suggesting that local environments varied in their ability to support mass gain and positive energy balance. As mean body condition improved across populations, the magnitude of the survival cost of reproduction increased, linear selection on body size shifted from positive to negative, and quadratic selection shifted from stabilizing to weakly disruptive. Our results suggest that reproductive trade-offs and patterns of phenotypic selection in female brown anoles are more sensitive to inferred variation in environmental quality than to experimentally induced variation in predation.

Selection on Sperm Count, but Not on Sperm Morphology or Velocity, in a Wild Population of Anolis Lizards

Sperm competition is a widespread phenomenon that shapes male reproductive success. Ejaculates present many potential targets for postcopulatory selection (e.g., sperm morphology, count, and velocity), which are often highly correlated and potentially subject to complex multivariate selection. Although multivariate selection on ejaculate traits has been observed in laboratory experiments, it is unclear whether selection is similarly complex in wild populations, where individuals mate frequently over longer periods of time. We measured univariate and multivariate selection on sperm morphology, sperm count, and sperm velocity in a wild population of brown anole lizards (Anolis sagrei). We conducted a mark-recapture study with genetic parentage assignment to estimate individual reproductive success. We found significant negative directional selection and negative quadratic selection on sperm count, but we did not detect directional or quadratic selection on any other sperm traits, nor did we detect correlational selection on any trait combinations. Our results may reflect pressure on males to produce many small ejaculates and mate frequently over a six-month reproductive season. This study is the first to measure multivariate selection on sperm traits in a wild population and provides an interesting contrast to experimental studies of external fertilizers, which have found complex multivariate selection on sperm phenotypes.

Hormonal pleiotropy structures genetic covariance.

Quantitative genetic theory proposes that phenotypic evolution is shaped by G, the matrix of genetic variances and covariances among traits. In species with separate sexes, the evolution of sexual dimorphism is also shaped by B, the matrix of between‐sex genetic variances and covariances. Despite considerable focus on estimating these matrices, their underlying biological mechanisms are largely speculative. We experimentally tested the hypothesis that G and B are structured by hormonal pleiotropy, which occurs when one hormone influences multiple phenotypes. Using juvenile brown anole lizards (Anolis sagrei) bred in a paternal half‐sibling design, we elevated the steroid hormone testosterone with slow‐release implants while administering empty implants to siblings as a control. We quantified the effects of this manipulation on the genetic architecture of a suite of sexually dimorphic traits, including body size (males are larger than females) and the area, hue, saturation, and brightness of the dewlap (a colorful ornament that is larger in males than in females). Testosterone masculinized females by increasing body size and dewlap area, hue, and saturation, while reducing dewlap brightness. Control females and males differed significantly in G, but treatment of females with testosterone rendered G statistically indistinguishable from males. Whereas B was characterized by low between‐sex genetic correlations when estimated between control females and males, these same correlations increased significantly when estimated between testosterone females and either control or testosterone males. The full G matrix (including B) for testosterone females and either control or testosterone males was significantly less permissive of sexually dimorphic evolution than was G estimated between control females and males, suggesting that natural sex differences in testosterone help decouple genetic variance between the sexes. Our results confirm that hormonal pleiotropy structures genetic covariance, implying that hormones play an important yet overlooked role in mediating evolutionary responses to selection.

Natural nest substrates influence squamate embryo physiology but have little effect on hatchling phenotypes.

Vertebrate embryos require access to water; however, many species nest in terrestrial habitats that vary considerably in moisture content. Oviparous, non-avian reptiles have served as models to understand how environmental factors, like moisture availability, influence development because eggs are often exposed to prevailing environments in the absence of parental care. Though much research demonstrates the importance of water absorption by eggs, many ecological factors that influence moisture availability in natural nests have received little attention. For example, the type of substrate in which nests are constructed is understudied. We experimentally incubated eggs of the brown anole lizard (Anolis sagrei) in 2 naturally occurring nest substrates that were treated with varying amounts of water to determine how natural substrates influence development at different moisture concentrations. One substrate consisted of sand and crushed seashells and the other was mostly organic material (i.e. decayed plant material). Both are common nesting substrates at our field site. When controlling for water uptake by eggs, we found that egg survival and hatchling phenotypes were similar between substrates; however, embryos developed more quickly in the sand/shell substrate than the organic substrate, indicating substrate-specific effects on embryo physiology. These results demonstrate that different natural substrates can result in similar developmental outcomes if the water available to eggs is comparable; however, some aspects of development, like developmental rate, are affected by the type of substrate, independent of water availability. Further study is required to determine how natural substrates influence embryo physiology independent of water content.

FIRST RECORD OF Gonatodes albogularis DUMÉRIL & BIBRON, 1836 (SQUAMATA: SPHAERODACTYLIDAE) FOR THE DEPARTMENT OF ATLÁNTIDA, HONDURAS, WITH COMMENTS ON THE INTERACTIONS WITH OTHER LIZARDS

We recorded the first population of Gonatodes albogularis for the Departmento de Atlántida, being the most northwestern record in Honduras and we comment on its possible origin. In addition, in the same locality, we found Hemidactylus frenatus and Norops sagrei, species not native to Honduras. We observe certain behaviors of individuals of these three species and discuss them with respect to previous information on their possible interactions, with the intent to encourage future research on the interactions of these three species.

Tails of reproduction: Regeneration leads to increased reproductive investment.

Trade-offs between life-history traits are due to limited resources or constraints in the regulation of genetic and physiological networks. Tail autotomy, with subsequent regeneration, is a common anti-predation mechanism in lizards and is predicted to trade-off with life-history traits, such as reproduction. We utilize the brown anole lizard with its unusual reproductive pattern of single-egg clutches every 7-10 days to test for a trade-off in reproductive investment over 8 weeks of tail regeneration on a limited diet. In contrast to predictions, we found that investing in tissue regeneration had a positive effect on reproduction in terms of egg size (11.7% relative to controls) and hatchling size (11.5% relative to controls), and no effect on egg number or survival, with the increase in reproduction starting at peak regeneration. We discuss mechanistic hypotheses that the process of regeneration may cause increased energetic efficiency or utilized shared physiological pathways with reproductive investment.

Habitat structure mediates vulnerability to climate change through its effects on thermoregulatory behavior

AbstractTropical ectotherms are thought to be especially vulnerable to climate change because they are thermal specialists, having evolved in aseasonal thermal environments. However, even within the tropics, habitat structure can influence opportunities for behavioral thermoregulation. Open (and edge) habitats likely promote more effective thermoregulation due to the high spatial heterogeneity of the thermal landscape, while forests are thermally homogenous and may constrain opportunities for behavioral buffering of environmental temperatures. Nevertheless, the ways in which behavior and physiology interact at local scales to influence the response to climate change are rarely investigated. We examined the thermal ecology and physiology of two lizard species that occupy distinct environments in the tropics. The brown anole lizard (Anolis sagrei) lives along forest edges in The Bahamas, whereas the Panamanian slender anole (Anolis apletophallus) lives under the canopy of mature forests in Panama. We combined detailed estimates of environmental variation, thermoregulatory behavior, and physiology to model the vulnerability of each of these species. Our projections suggest that forest‐dwelling slender anoles will experience severely reduced locomotor performance, activity time, and energy budgets as the climate warms over the coming century. Conversely, the forest‐edge‐dwelling brown anoles may use behavioral compensation in the face of warming, maintaining population viability for many decades. Our results indicate that local habitat variation, through its effects on behavior and physiology, is a major determinant of vulnerability to climate change. When attempting to predict the impacts of climate change on a given population, broad‐scale characteristics such as latitude may have limited predictive power.

Ocular elongation and retraction in foveated reptiles.

Pronounced asymmetric changes in ocular globe size during eye development have been observed in a number of species ranging from humans to lizards. In contrast, largely symmetric changes in globe size have been described for other species like rodents. We propose that asymmetric changes in the three-dimensional structure of the developing eye correlate with the types of retinal remodeling needed to produce areas of high photoreceptor density. To test this idea, we systematically examined three-dimensional aspects of globe size as a function of eye development in the bifoveated brown anole, Anolis sagrei. During embryonic development, the anole eye undergoes dynamic changes in ocular shape. Initially spherical, the eye elongates in the presumptive foveal regions of the retina and then proceeds through a period of retraction that returns the eye to its spherical shape. During this period of retraction, pit formation and photoreceptor cell packing are observed. We found a similar pattern of elongation and retraction associated with the single fovea of the veiled chameleon, Chamaeleo calyptratus. These results, together with those reported for other foveated species, support the idea that areas of high photoreceptor packing occur in regions where the ocular globe asymmetrically elongates and retracts during development.

Sex-Specific Population Differences in Resting Metabolism Are Associated with Intraspecific Variation in Sexual Size Dimorphism of Brown Anoles.

AbstractSexual size dimorphism can vary in direction and magnitude across populations, but the extent to which such intraspecific variation is associated with sex and population differences in underlying metabolic processes is unclear. We compared resting metabolic rates (RMRs) of brown anole lizards (Anolis sagrei) from two island populations in the Bahamas (Eleuthera and Great Exuma) that differ in the magnitude of male-biased sexual size dimorphism. Whereas females from each population exhibit similar growth rates and body sizes, males from Great Exuma grow more quickly and attain larger body sizes than males from Eleuthera. We found that these population differences in growth of males persisted in captivity. Therefore, we predicted that males from each population would differ in RMR, whereas females would not. Consistent with this prediction, we found that RMR of males from Eleuthera was higher than that of males from Great Exuma, particularly at higher temperatures. As predicted, RMR of females did not differ between populations. Despite this apparent sex-specific trade-off between growth rate and RMR at the population level, we found a positive relationship between growth rate and RMR at the individual level. The fact that Great Exuma males maintain lower RMR than Eleuthera males, despite their greater absolute growth rates and the positive relationship between RMR and growth rate across individuals, suggests that Great Exuma males may have lower baseline metabolic demands and/or greater growth efficiency than Eleuthera males. Our results call attention to sex-specific divergence in metabolism as a potential mechanism for intraspecific divergence in sexual size dimorphism.