The island–mainland species turnover relationship

Many oceanic islands are notable for their high endemism, suggesting that islands may promote unique assembly processes. However, mainland assemblages sometimes harbour comparable levels of endemism, suggesting that island biotas may not be as unique as is often assumed. Here, we test the uniqueness of island biotic assembly by comparing the rate of species turnover among islands and the mainland, after accounting for distance decay and environmental gradients. We modelled species turnover as a function of geographical and environmental distance for mainland (M–M) communities of Anolis lizards and Terrarana frogs, two clades that have diversified extensively on Caribbean islands and the mainland Neotropics. We compared mainland–island (M–I) and island–island (I–I) species turnover with predictions of the M–M model. If island assembly is not unique, then the M–M model should successfully predict M–I and I–I turnover, given geographical and environmental distance. We found that M–I turnover and, to a lesser extent, I–I turnover were significantly higher than predicted for both clades. Thus, in the first quantitative comparison of mainland–island species turnover, we confirm the long-held but untested assumption that island assemblages accumulate biodiversity differently than their mainland counterparts

Do the relationships between hindlimb anatomy and sprint speed variation differ between sexes in Anolis lizards?

The ability of an animal to run fast has important consequences on its survival capacity and overall fitness. Previous studies have documented how variation in the morphology of the limbs is related to variation in locomotor performance. Although these studies have suggested direct relations between sprint speed and hindlimb morphology, few quantitative data exist. Consequently, it remains unclear whether selection acts in limb segment lengths, overall muscle mass or muscle architecture (e.g. muscle fiber length and cross-sectional area). Here, we investigate whether muscle architecture (mass, fiber length and physiological cross-sectional area), hindlimb segment dimensions, or both, explain variation in sprint speed across 14 species of Anolis lizards. Moreover, we test whether similar relationships exist between morphology and performance for both sexes, which may not be the case given the known differences in locomotor behavior and habitat use. Our results show that the main driver of sprint speed is the variation in femur length for both males and females. Our results further show sexual dimorphism in the traits studied and, moreover, show differences in the traits that predict maximal sprint speed in males and females. For example, snout vent length and overall muscle mass are also good predictors of sprint speed in males, whereas no relationships between muscle mass and sprint speed was observed in females. Only a few significant relationships were found between muscle architecture (fiber length, cross-sectional area) and sprint speed in male anoles, suggesting that overall muscles size, rather than muscle architecture, appears to be under selection

Stumped by trees? A generalized null model for patterns of organismal diversity

Journal ArticleEvolutionary biologists increasingly have become interested in the factors determining the structure of phylogenetic trees. For example, highly asymmetric trees seem to suggest that the probability of extinction and/or speciation differs among lineages

Evolutionary biology for the 21st century

New theoretical and conceptual frameworks are required for evolutionary biology to capitalize on the wealth of data now becoming available from the study of genomes, phenotypes, and organisms - including humans - in their natural environments.Molecular and Cellular BiologyOrganismic and Evolutionary Biolog

Anolis Newsletter VII

Newsletter for the 7th Anolis Symposium, Fairchild Tropical Botanic Gardens, Miami, Florida, 17-18 March 2018. It had been nearly a decade since the previous Anolis symposium was held in Cambridge, MA, at the Museum for Comparative Zoology, Harvard. A reunion of anole biologists en masse was long past due and it was decided that this symposium would be slightly different – we were going to hold it somewhere with anoles! And so, on the weekend of 17-18th March, 2018, nearly 70 anole biologists traveled to sunny south Florida to attend the 7th Anolis Symposium held at the beautiful Fairchild Tropical Botanic Gardens in Miami. In the grounds of the botanical gardens, attendees were presented with a diverse community of six (!) species of anole, both native and non-native, representing four distinct ecomorphs

Adaptation, Speciation, and Convergence: A Hierarchical Analysis of Adaptive Radiation in Caribbean Anolis Lizards

This is the publisher's version, also available electronically from http://www.bioone.org/doi/abs/10.3417/0026-6493%282006%2993%5B24%3AASACAH%5D2.0.CO%3B2.Caribbean Anolis lizards are a classic case of adaptive radiation, repeated four times across islands of the Greater Antilles. On each island, very similar patterns of evolutionary divergence have occurred, resulting in the evolution of the same set of ecological specialists—termed ecomorphs—on each island. However, this is only part of the story of the Caribbean anole radiations. Indeed, much of the species diversity of Caribbean Anolis occurs within clades of ecomorphs, which contain as many as 14 ecologically-similar species on a single island. We ask to what extent the classic model of ecological interactions as the driving force in adaptive radiation can account for this aspect of anole evolutionary diversity. Our answer is that it can in part, but not entirely. More generally, the most complete understanding of evolutionary diversification and radiation is achieved by studying multiple hierarchical evolutionary levels from clades to populations

Predator-driven natural selection on risk-taking behavior in anole lizards

Biologists have long debated the role of behavior in evolution, yet understanding of its role as a driver of adaptation is hampered by the scarcity of experimental studies of natural selection on behavior in nature. After showing that individual Anolis sagrei lizards vary consistently in risk-taking behaviors, we experimentally established populations on eight small islands either with or without Leiocephalus carinatus, a major ground predator. We found that selection predictably favors different risk-taking behaviors under different treatments: Exploratory behavior is favored in the absence of predators, whereas avoidance of the ground is favored in their presence. On predator islands, selection on behavior is stronger than selection on morphology, whereas the opposite holds on islands without predators. Our field experiment demonstrates that selection can shape behavioral traits, paving the way toward adaptation to varying environmental contexts

Head Size of Male and Female Lizards Increases with Population Density Across Island Populations in the Bahamas

In polygynous lizards, male–male competition is an important driver of morphologic and behavioral traits associated with intraspecific dominance. The extent to which females engage in aggressive behavior and thus contribute to competition-driven morphologic variation is not well studied. We used injury frequencies of brown anoles (Anolis sagrei) in 16 island populations to test the hypothesis that injury-inducing aggressive encounters increase with population density in both male and female lizards. We further asked whether intraspecific competition is a potential driver of phenotypic traits related to dominance by using population density as proxy for intraspecific competition. We found that the proportion of individuals with injuries was greater in populations with higher densities, suggesting that agonistic competitive interactions increase with population density. Size-adjusted head length of male and female lizards increased with population density, suggesting that larger heads might be advantageous when intraspecific competition is strong. We detected differences in morphology and injury frequency among islands for both males and females, which suggests that agonistic competitive interactions among females may be stronger than previously appreciated. Further research is needed to determine whether aggressive encounters involving females are restricted to intrasexual competition or whether they also involve males, and how morphologic traits of females are related to competitive dominance and reproductive success

A second Anolis lizard in Dominican amber and the systematics and ecological morphology of Dominican amber anoles.

A fossil Anolis lizard in the collections of the American Museum of Natural History is the second anole preserved in amber from the Dominican Republic (Miocene epoch) to be studied..

Favorable Climate Change Response Explains Non-Native Species' Success in Thoreau's Woods

Invasive species have tremendous detrimental ecological and economic impacts. Climate change may exacerbate species invasions across communities if non-native species are better able to respond to climate changes than native species. Recent evidence indicates that species that respond to climate change by adjusting their phenology (i.e., the timing of seasonal activities, such as flowering) have historically increased in abundance. The extent to which non-native species success is similarly linked to a favorable climate change response, however, remains untested. We analyzed a dataset initiated by the conservationist Henry David Thoreau that documents the long-term phenological response of native and non-native plant species over the last 150 years from Concord, Massachusetts (USA). Our results demonstrate that non-native species, and invasive species in particular, have been far better able to respond to recent climate change by adjusting their flowering time. This demonstrates that climate change has likely played, and may continue to play, an important role in facilitating non-native species naturalization and invasion at the community level