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Sure, they mostly live on the other side(s) of the world, they use sounds rather than dewlaps, and you mostly see them at night.

But some anoles you could only spot at night!

And geckos are mostly tropical! And there are a lot of them! And they don’t like to lay many eggs at a time – heck, some of them even have dewlaps! And they have radiated like crazy (1860 species and counting).

Want to know more? Want to tell us more?

See you in Tel Aviv, Israel, at the end of May 2019 at Gekkota Mundi II: the second conference for gecko biologists from around the world

For more details write us:  gekkotamundi19@gmail.com

or see: https://gekkotamundi-ii.weebly.com/

In a study hot off the press, Gilles de Meester and colleagues examine the phylogenetic distribution of brain size across squamates (lizards and snakes; you can find a reference and a link to the study at the bottom). In it, the authors explore the hypothesis that larger brains evolved to allow organisms to better manage environmental complexity, through enhanced cognition and behavioral flexibility. Despite years of hypothesis testing on the subject, there is no clear consensus about its validity. De Meester et al. join the quest and investigate the relationship of brain size in 171 squamate species (including 8 anoles!) to habitat type and degree of sociality. The punchline is that snakes are the pea-brains of the squamate world. Unexpectedly, there was a strong positive relationship between degree of sociality and brain size, such that solitary species had the largest brains. And, perhaps less supported but still a trend; arboreal species generally have the largest brains, while fossorial species (those that burrow and live in the leaf litter) have the smallest.

From De Meester et al.: Ancestral state reconstruction of relative brain size (residuals of the brain to body mass regression) along the nodes and branches of the phylogenetic tree of 171 species of Squamata. Sphenodon punctatus is included as an outgroup. Species with positive residuals (blue) have large brains relative to their body size, whereas species with negative residuals (yellow–red) have small brains relative to their body size. Results were visualized using the contMap function in R (package phytools; Revell, 2012) 

But, I hear you say, what of the anoles? Well, Neotropical species had the largest brains of any biogeographical region, and anoles specifically are exceptionally big brained. In fact, on delving into the supplementary material — in which De Meester et al. provide wonderful access into the brain size data that they accumulated — it reveals that Anolis stratulus, the Puerto Rican trunk-crown spotted anole, has the relatively largest brain size of any squamate!

Here is a crude figure I just whipped up from the De Meester et al. dataset. As it shows, anoles perform very well in the brain size department relative to both all squamates and within lizards specifically. Although the American green anole (A. carolinensis) does let the team down slightly…

You can read the study in full following the link below!

Gilles De Meester, Katleen Huyghe, Raoul Van Damme. 2019. Brain size, ecology and sociality: a reptilian perspective. Biological Journal of the Linnean Society, bly206.
https://doi.org/10.1093/biolinnean/bly206

From the archives. One of the greatest <i>Anole Annals</i> posts of all times, because why not?

“You’ve gotta see this!” my fiancé Mark called to me one morning.  He was outside, which could mean only one thing: a wildlife encounter was underway.  Living in a semi-rural neighborhood in Florida, you never knew what you would see, from a mated pair of Sandhill Cranes walking down the street with their young, to Gopher Tortoises excavating burrows in the front yard.

I walked downstairs to the concrete area under our elevated house where Mark was staring at something on the ground.  I looked down to see a frog (Cuban Treefrog) with the tail of an A. carolinensis protruding from its gullet.

“I knew that lizard,” Mark said forlornly.

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I wanted to share an observation of communal basking of the Green Anole (Anolis carolinensis) from the western Highland Rim of Tennessee. The locality is near the northern extent of their range in middle Tennessee. On a warm January day this winter, I observed six (6) individuals basking in close proximity along an exposed tree branch. The overwintering habitat was a south-facing road cut.

Has anyone else observed this type of “communal” basking of anoles, either in the Green Anole (Anolis carolinensis) or other species?

Shelby Irwin, a junior in Michele Johnson’s lab at Trinity University, presented a poster on her summer research in Thomas Sanger’s lab at Loyola University examining hatchling behavior in Anolis sagrei after incubation in thermally stressful conditions. In the lab, Irwin and colleagues incubated A. sagrei eggs under a standard (27°C) and elevated (34°C) thermal regimes to investigate impacts on hatchling phenotype and behavior.

It has been previously noted that thermal stress during development can affect craniofacial development, but Shelby was interested in if there was also an impact on behavior of hatchlings. After hatching, lizards from both the standard and elevated thermal regimes were run through a gambit of exploratory (prey interactions, novel object, and open-field test) and social trials (conspecific and predator interactions). They found that “hot” hatchlings were less aggressive and exhibited less exploratory behaviors. Their findings add to the growing body of research investigating the impacts of a warming world, particularly with regards to sensitive periods in thermally sensitive species.

Recent increases in non-native species introductions by humans have spurred a flurry of research examining the subsequent impacts of species invasions. However, often times non-native species introductions go unnoticed until the species is already established. When predicting the effects of a species invasion, it is important to understand how population demographics change during the colonization and establishment stages. Amélie Fargevieille addressed this issue in her talk entitled “Population demographics of an invasive lizard following experimental introduction on small islands.”

Fargevieille and colleagues released adult Anolis sagrei onto islands off the northeast coast of Florida prior to the reproductive season and monitored survival and reproduction over the first reproductive season. The total density of lizards introduced to islands were the same, but four of their islands were introduced with male-biased populations and four with female-biased populations. They then examined the survival and reproduction of the descendants of the founding populations over the next two years. They found that male-biased and female-biased founding populations did not differ in survival rates. In addition, across all islands, juveniles had the highest mortality, which suggests that the ecological factors facilitating or deterring colonization in the earliest stages following an introduction play an important role in invasion biology. Looking forward to future work from Fargevieille and colleagues in the Warner lab!

Anolis shrevei. Photograph by Miguel Landestoy.

Post-doc Vincent Farallo presented work, co-authored by Martha Muñoz, in the behavioral physiology session on the importance of incorporating physiology and behavior when assessing how species, especially montane endemics, will be impacted by climate change. Vincent and Martha compared correlative models and mechanistic niche models to better understand how climate change may impact three anoles from the island of Hispaniola, Anolis shrevei, A. armouri, and A. cybotes. When predicting future ranges of these species using correlative modeling, Farallo and Muñoz saw that the ranges of the mountain-top endemics A. shrevei and A. armouri shrink, whereas the range of the widespread species A. cybotes remains the same under future climate change predictions. Comparing these findings to mechanistic niche modeling, which uses organismal physiology and behavior to help predict future activity times within current ranges, they found that all three species will increase activity times within the mountain-top endemic ranges.

To reiterate their findings, they showed that when incorporating behavior and physiology, montane endemic species will increase potential activity time under climate change.  However, their widespread competitor will also see increased activity, indicating the montane endemics are still likely at risk, but not directly from warming temperatures.  Understanding the mechanism of species decline will be critical for mitigating the impacts of climate change.

Despite the widespread use of anoles as model species for ecology, evolution, and behavior, we still have a relatively poor understanding of their nesting behavior and the factors that contribute to egg survival. This is unfortunate because past research demonstrates that egg survival can drive important measures of population demography (e.g. adult population density, Andrews 1982). Andrew DeSana, an undergrad from Seton Hill University, teamed up with the Warner lab to explore the possibility that marsh crabs (Armases cinereum) might serve as predators for brown anole eggs (Anolis sagrei). Because nest site selection by females may shield developing eggs from predators, he also wanted to know how several common nesting microhabitats might influence the depredation of eggs. He used both a lab and a field study to assess how the density of crab predators (no crabs, low crab density, and high crab density) and the nesting microhabitat of females (open sand, under palm fronds, and under leaf litter) might influence egg survival. He collected eggs from a breeding colony of anoles and placed them in these microhabitats in the presence of varying densities of crabs.

He found that marsh crabs readily prey upon anole eggs and that variation in egg survival was best explained by both crab density and the microhabitat where eggs develop. In both the lab and field study, eggs had the highest survival when placed under leaf litter and lower survival in the open and under palm fronds. Anecdotal data of crab behavior suggests that they don’t forage in the leaf litter and this may explain these results. Egg survival also decreased with increasing crab density. Thus, females nesting in leaf litter in habitats with low crab density would have greater reproductive success than those nesting in other microhabitats, especially if crab density is high. Future research will determine how the presence/absence of crabs influences female nesting behavior.

Andrews, R.M., 1982. Spatial variation in egg mortality of the lizard Anolis limifrons. Herpetologica, pp.165-171.

Many biologists are interested in understanding how temperature affects animals throughout ontogeny. Egg incubation experiments are often done to examine how nest temperatures influence embryo development. However, the information gleaned from these experiments are only useful when comparing ecologically relevant thermal regimes.

Mallory Turner, an undergraduate researcher in the Warner lab at Auburn University, examined how embryo development differs between incubator thermal regimes in Anolis cristatellus and A. sagrei. Nest temperatures peak at different times of the day due to differences in the local environment (e.g., habitat structure, shade, etc.). Turner examined how incubator thermal regimes that were uncentered and peak-centered influenced development. Nest temperature data were used to create two 24-hour diel cycles. Anole eggs were incubated in incubators programmed to mimic hourly nest temperature data with temperatures either uncentered (uncentered regime), or with hourly nest temperature data aligned temporally at thermal peaks (peak-centered regime). She examined how thermal regimes impacted incubation duration and offspring phenotype. Incubator thermal regime did not impact incubator duration, mass, or SVL in either anole species. Uncentered thermal regimes have lower maximum incubation temperatures compared to peak-centered regimes, although interestingly enough these differences do not appear to influence development.

Frequently phenotypic evolution is rapid on islands, resulting in many ecologically diverse species. Most of what we know about the faster evolution on islands has been through the examination of morphological diversity. By utilizing species-rich Anolis lizards, Dr. Martha Muñoz and collaborators were able to examine the island effect with regards to rates and patterns of evolution through a different lens: thermal physiological trait diversity. Muñoz et al. examined the evolutionary dynamics of cold tolerance, body temperature, and heat tolerance in island and mainland anoles. They discovered faster heat tolerance evolution in the mainland lineages, and that island and mainland anoles are evolving towards separate trait optima with island lizards having a higher upper thermal limit. A higher optima and slower evolutionary rates are consistent with the Bogert Effect, in which organisms are shielded from selection because of behavioral buffering such as thermoregulatory behavior. Cold tolerance did not differ between habitats, not surprisingly due the fact that lower physiological limits cannot be behaviorally buffered against selection. Despite island and mainland anoles occurring in similar thermal environments, island lizards thermoregulate more. Consequently, the ecological opportunity (fewer predators and/or competitors) provided on islands may be reducing the costs of thermoregulation and slowing down, rather than accelerating evolution of certain traits. This study highlights the importance of other phenotypic axes that organisms diversify along in an adaptive radiation, such as physiological diversification, and that behavior can elucidate or drive patterns shaping evolution.