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One of the few known Anolis roosevelti specimens.

Anole stalwart Greg Mayer gave a wonderful talk discussing the distribution and morphology of the large and maybe-extinct Anolis roosevelti. A. roosevelti, commonly known as the Culebra Island giant anole, was first described in 1931 by Chapman Grant, a US Army Major and practising herpetologist, from a single adult male specimen collected on Culebra. Although Reinhardt and Lutken, in 1863, had already provided an accurate description of A. roosevelti, but under an alternative name of A. velifer.

Reinhardt and Lutken’s specimens were collected from Vieques, Tortola, and St. John, although Greg having the opportunity to study them meant tracking them down to natural history collections in both Copenhagen and Stockholm. In total, this entire species is known from eight specimens, only six of which are still in existence (Greg had the opportunity to study all six, meaning he’s now seen more roosevelti than any other anolologist?). Greg explains that roosevelti based on the limited information provided by Dimas Villanueva, who collected the holotype, and his own investigations, roosevelti can be classified as a “crown-giant” ecomorph. This means that the eastern islands of the Puerto Rico bank had a series of four ecomorphs, with roosevelti being what Ernest Williams termed a climatic vicariant of cuvieri, occuring in (and presumably being adapted to) the more xerophytic forests of the eastern bank islands.

The known distribution of Anolis roosevelti.

Greg went on to describe the morphological features which distinguish A. roosevelti from a A. cuivieri, an ecologically and morphologically similar species from neighbouring Puerto Rico. Roosevelti is a larger, brownish gray rather than green as is seen in cuvieri (although check out these gray cuvieri preveiously mentioned on AA). Roosevelti generally has larger head scales, and a more elongate and deeply grooved head – these differences are confirmed in the ANCOVA analyses below.

So, what chances are there of seeing roosevelti in the wild? Low, probably. No specimens have been collected since 1932, and several researchers, including Greg, have recently scoured both Vieques, St. John and Tortola but with no success. By far the most extensive searches have been conducted by Ava Gaa, who exhaustively searched Culebra (totalling 1500 hours of looking!) as well as short visits to Vieques and St. John all with no success. Tantalising reports of potential candidates turned out to be juvenile green iguanas. Greg concludes by recommending that the long-protected and relatively poorly explored eastern half of Vieques may hold the secret to if any populations remain.

The gold dust day gecko was introduced to Hawaii in the 1980s. It is ecologically similar to the green anole, which was introduced to Hawaii in the 1950s.

Hawaii has no native herpetofauna, aside from sea turtles. Human-mediated introductions between the 1950s and 1980s have created an interesting new guild of arboreal and diurnal lizards: the green anole (Anoles carolinensis), the gold dust day gecko (Phelsuma laticauda) and the brown anole (A. sagrei ).

Amber Wright next to her poster on Saturday

Phelsuma laticauda belongs to a genus that is endemic to Madagascar with almost 50 species, that are known for their incredible color patterns. Anolis carolinensis and P. laticauda are thought to be ecologically similar and thus potential competitors.

Amber Wright’s research investigates whether and how the three species partition their habitat when they occur in sympatry and how that might affect species abundance. Using field observations and morphological data, she found that the three species overlap in body size and habitat use, which suggests that they are potential competitors for food resources and perch sites.

Enclosure experiment.

Preliminary data show that abundance decreases when ecologically similar species are present.

In a pilot study, Amber used seven 10x10m plots to simulate different community scenarios: only one species, two species and all three species. Anolis carolinensis and A. sagrei seem to be interacting similarly to populations outside of Hawaii: coexistence with reduced densities and increased perch heights of A. carolinensis. When all three species were present, P. laticauda perched higher than usual, presumably to avoid competition with A. carolinensis. Future work will focus on long term effects of species composition on resource partitioning and abundance of each species.

Reptiles are often thought of as solitary and not social animals. However, all of us who study anoles know that Anolis are anything but solitary animals. Spend a few minutes observing an anole and you might see it dewlapping, doing push-ups, tail wagging, and fighting with other males or even other anoles species.  James Stroud, a Ph.D. candidate from the Feeley lab @ Florida International University, presented on Saturday about the exploratory results of a new research method he and Robert Heathcote have started to construct social networks of A. sagrei and A. cristatellus in Miami, Florida. A. sagrei and A. cristatellus are similar in morphology and ecology and they wanted to learn how patterns of social interactions between these two species allow them to coexist outside of their native range.

Individual social behavior manifests itself collectively at the population level and interactions between populations (within and between species) might act as a basis for evolutionary processes. James and Robert tagged both male and female anoles in their study to track and recapture the animals in the future for a long term study. They measured the distance between every two anoles observed and inferred the strength of interaction as stronger if the anoles were closer to each other. Both species show a great web of interactions both within and between species. Some individuals are also much more “bold,” interacting with many males and females of either species, while others show fewer social interactions. These preliminary data are exciting since so little is known about Anolis social behavior. James also mentioned that they will be including additional data such as the types of interactions that will add great complexity and insight to this story.

Kristin Winchell, my fellow lab mate at the Revell lab, presented her work on the habitat use of two urban dwellers in Puerto Rico. Past studies have shown that Anolis cristatellus and Anolis stratulus vary in abundances and use different portions of the natural habitat. As early as 1964, Rand showed that A. stratulus was less abundant and perched higher on trees in forest habitat. However, we know very little about whether these patterns are maintained in urban areas where species have access to novel manmade structures. To address this, Kristin evaluated the habitat use of these two species across seven urban replicates and contrasted it to the available habitat. She found that urban A. stratulus uses more isolated perches with greater vegetative canopy and perches at higher portions of the habitat. Anolis cristatellus uses perches that are less isolated, shaded mostly by manmade canopy (i.e. buildings and houses) and at lower heights. When examining these patterns in a multidimensional space, she showed that A. cristatellus has expanded its urban niche through the use of manmade structures, while A. stratulus uses a subset of the natural portion of the habitat that A. cristatellus also uses.

Her research shows that these two urban dwellers interact with the novel portions of the habitat differently. Anolis cristellus has expanded its niche towards manmade structures which has implications for adaptation to enhance stability and locomotion when using these structures as shown in some of her previous work (Winchell, et al, 2016).  Anolis stratulus uses the less available remnants of the natural habitat which may have implication for conservation if they become sparser as urbanization expands.

Alexandra Herrera presented on using genetic population structure to understand how geographical processes have shaped genetic isolation of three widespread Anolis species on the Puerto Rican Bank. Geographical processes are an important event in shaping current populations and can lead to interesting patterns of diversification. However, these processes may not necessarily affect species similarly. In this study, Alexandra used a combination of nuclear genes and one mitochondrial gene to examine the population structure of these three anoles.

Evidence strongly suggests that populations of Anolis pulchellus were separated into two major clades through the formation of mountains. These two clades are made up of one cluster from south Puerto Rico and a cluster that includes both Northeast Puerto Rico and the Virgin Islands.

The diversification of the other two species corresponds with tectonic and sea level changes. For Anolis stratulus, divergence between populations in PR, Culebra, Vieques and the Virgins Islands occurred at the end of the Pliocene after the formation of the Virgin Passage.  These populations formed five clusters east PR, south PR, Virgin Islands, Vieques-Culebra and Peter-Norman islands.

For Anolis cristatellus the divergence between east PR and south PR with the Virgin Islands was estimated around the late Miocene-Pliocene transition when the Mona and Virgin Island passages formed. These populations formed 4 clusters east PR, south PR,  Virgin Islands and Carrot Rock-Peter-Culebra-Piñeiro.

This research shows that each species had a different diversification pattern and that they all occurred around the middle of late Pleistocene. Furthermore, geographical processes may affect species differently, leading to various patterns of population structures.

For many years, biologists believed that evolution was a process that played out over vast stretches of geological time and would not be observable during field studies. More recent research, however, has begun to show that evolution can occur very quickly and that experiments in the field can address evolution in action. Tom Schoener, eminent professor at the University of California, Davis, shed light on our evolving view of how evolution occurs in his talk, “Eco-evolutionary Aspects of the Lizard Anolis sagrei in an Island Metapopulation” at JMIH 2016.

By introducing a novel predator, the curly-tailed lizard (Leiocephalus carinatus), which devours anoles, to a series of small islands in the Bahamas, Schoener and colleagues were able to observe evolutionary responses in A. sagrei in fewer than 10 years. By preying on A. sagrei, curly-tailed lizards induced behavioral changes in perch height, and created selection for relatively longer limbs that increase anoles’ ability to escape this predator. Curly-tailed lizards also caused a variety of ecological effects, including reducing anole populations and changing arthropod abundance, which may affect the future evolution of anoles on these islands. Ongoing monitoring shows that these anole populations seem to be rebounding and that different types of selection may be acting on hindlimb length.

A curly-tailed lizard (Leiocephalus carinatus) displays its namesake in Florida. Photo by Ianaré Sévi.

Perhaps not surprisingly, many of the experimental islands were occasionally devastated by hurricanes which are becoming more frequent and more powerful in the Caribbean. While these extreme weather events interrupted some of Schoener’s planned research, they also provided a unique opportunity to study how hurricanes may cause natural selection. Schoener found that anoles which survived hurricanes had longer hindlimbs, and these lizards were better able to hold onto trees and other perches at high wind speeds, likely increasing survival of hurricanes by preventing lizards being blown out to sea! Taken together this body of research suggests that novel environmental changes, such as invasive species or increasingly extreme weather, exert selection on organisms and that we can observe these organisms evolving rapidly on ecological timescales.

Previous research in the Warner lab has shown that temperature during egg development influences fitness and performance in Anolis sagrei. In particular, a warmer incubation temperature increases sprint speed. The breeding season of A. sagrei spans from March through October, with lower temperatures early in the season and higher temperatures late in the season. Phil Pearson, a masters student in the Warner Lab, conducted an experiment to test whether embryos are developmentally adapted to their incubation temperature. He collected eggs from two temporally-separated cohorts and incubated them under two different temperatures, simulating seasonal temperature differences. He found that late season hatchlings had higher egg survival when incubated under late season temperature. Regardless of incubation temperature, late season embryos had higher sprint speed, larger body size and longer tails. This might compensate for the late start, since they are competing with early cohort individuals in the population.

Late season hatchlings have higher sprint speed regardless of incubation temperature

Overall, this suggests that timing of oviposition has greater effect on morphology and performance than incubation temperature. Future analysis will show whether timing of oviposition affects survival. Phil released the hatchlings on small islands to measure fitness using a mark-recapture approach and will hopefully present his findings at future meetings.