The Lonely Clouded Anole on a Pacific Island

Anolis nebulosus

Anolis nebulosus. Photo by Hugo Siliceo-Cantero.

By H. Hugo Siliceo-Cantero and A. Garcia

In the late 1980´s, the scientists Bradford C. Lister and Andrés García discovered an interesting population of clouded anoles inhabiting the small 3.3 ha island of San Agustin located just off the Pacific coast of Jalisco, Mexico. This island was also close to the actual protected area of tropical dry forest on the mainland in the Chamela-Cuixmala Biosphere Reserve. Lister and García reported that the abundant anole population on San Agustin was maintained a decade later at much higher densities than the mainland population. We began to study this population in 2007 as a graduate student. Since then, we have studied several aspects of the ecology of this island population comparing this with the ecology of anoles on the mainland.

The existence of such island populations enables scientists to carry out natural experiments that provide invaluable information helping us to understand ecological and evolutionary processes.

This Clouded Anole (Anolis nebulosus) species that is on San Agustin Island is endemic to Mexico, and is of particular interest as this population has evolved in the absence of similar species of the same genus, or congeners. The species on the island also occupies a broad niche of perch height and a low number of lamellae, and is one of the most sedentary anoles known. Our work demonstrated that San Agustin population of the Clouded Anole has distinct morphological and genetic traits compared to conspecifics on the mainland.

Recently, we found that the insular population also presents distinct ecologic traits compared to those of the mainland population. In our manuscript “Assessing the relative importance of intra- and interspecific interactions on the ecology of Anolis nebulosus lizards from an island vs. a mainland population”, we suggest that the processes that drives the ecology and evolution of this insular population (intraspecific competition) differs from those that are important in the mainland (interspecific competition).

We believe that the results of our research on the insular population of anoles on San Agustin Island complement the scenario of Caribbean anoles, where congeneric competition is the key evolutionary driver. Furthermore, in our study, we used video cameras to provide direct evidence of predation, interspecific and intraspecific encounters and aggression, which was possible because the Clouded Anole is a sedentary lizard.

It has been a pleasant and rewarding experience for me to study the Clouded Anole. Although spending hours in the field observing a largely sedentary lizard may seem a little boring and tedious, the data from our studies have revealed a fascinating adaptation to the natural and social environment with unique physical, genetic, and ecological characteristics.

Currently, the population of Clouded Anoles on San Agustin has been dramatically reduced, almost to the point of extirpation. We think that two natural events, the hurricanes Jova in 2011 and Patricia in 2015, as well as invasive studies such as Hernández-Salinas et al. (2016) where they extracted 77 anoles from this small island, are the cause of the dramatic reduction in the Clouded Anole of San Agustin Island. As ecologists, we believe that research should not be done at the expense of the species or population under study, but should ensure that the population remains intact to continue along its evolutionary path, and further elucidate our understanding of the natural world around us.

We are currently monitoring both insular and mainland populations in order to understand and evidence the ecological implications of such natural and anthropogenic reduction on anole populations.

SICB 2018: Heat Stress and Deformed Faces

EmbryosIncubation temperature is an important factor in development for anoles (and other ectotherms). Thom Sanger, a professor at Loyola University in Chicago, IL, presented his research on how high temperatures affect brain formation in developing anole embyros. With the help of undergraduates and a high school summer intern, Dr. Sanger found that when developing eggs were heat-shocked, many embryos were lost (75%), but for those that survived, forebrains became smaller (In the figure, A is normal and B is deformed). Interestingly, malformation of the forebrain affects the size and shape of the face, and so surviving heat-shocked embryos exhibit cranial malformations. As Sanger continues his research, he will follow a neural degeneration hypothesis, which boils down to (no pun intended) the idea that thermal stress increases the rate of cell death, and the amount of cell death affects facial shape. While the effects of high temperature may seem alarming, Sanger notes that this does not happen very often in nature; females are generally pretty good at selecting suitable nest sites. But, because development is similar across reptile taxa, anoles can be an excellent model system to inform predictions about what may happen to species that are in danger.

Origins and Biogeography of the Anolis crassulus Subgroup

Anolis morazani. Photo by Josiah Townsend from iNaturalist.

The Anolis crassulus subgroup contains ten morphologically-conserved highland anole species found throughout Nuclear Central America. Its members have long been a source of headache for region’s systematists. To quote Meyer & Wilson (1971): “…specimens of the crassulus group from Guatemala and Mexico have a bewildering array of admixtures of the distinctive characters observed in Honduras… The inter-relationships of the populations… [of the crassulus group] are exceedingly complex, and… we are unable to suggest a satisfactory arrangement.” This was followed up 21 years later by McCranie, Wilson, & Williams (1992): “Clearly, a thorough analysis of crassulus-like specimens from throughout their range… is sorely needed”, and repeated by McCranie & Köhler (2015) 13 years after that.

Despite the need for a thorough investigation into this group, our understanding of the relationships and validity of these taxa has not improved much. This is partly because this subgroup has been poorly represented without broad sampling in larger-scale molecular phylogenies. Two samples in particular, an A. crassulus (from Chiapas, Mexico) and an A. sminthus (from Olancho, Honduras), have been continuously utilized, without additional samples from these species. Most recently, Nicholson et al. (2017; six species) and Poe et al. (2017; three) expanded the molecular sampling for this group, using single exemplars as part of broader analyses.

In a study published last month in BMC Evolutionary Biology, Josiah Townsend and I examined the evolutionary relationships of the majority of this subgroup, in order to provide a starting point for resolving some of the confusion surrounding these taxa.

Figure 4 from Hofmann & Townsend, 2017. Species tree of the Anolis crassulus subgroup. Inset photo: Anolis heteropholidotus (2) by JHT.

Fig. 4 from Hofmann & Townsend, 2017: Species tree of the Anolis crassulus subgroup. Black nodes indicate PP > 0.95; PP < 50 not shown. Inset photo: Anolis heteropholidotus (2) by JHT.

The results of our multilocus phylogenetic investigation gave us some interesting new insights into the subgroup. We found support for the monophyly of the A. crassulus subgroup relative to other Anolis (as opposed to its paraphyly, as recovered in Poe et al. 2017), and the validity of all of its species (excepting the two we could not sample). Additionally, we recovered considerable overlooked diversity within this subgroup. Anolis crassulus itself represents at least four lineages corresponding to distribution: the Chortis Highlands of Honduras, the Salvadoran Cordillera, Guatemala, and Chiapas, Mexico. Surprisingly, the sample from Chiapas previously used in many phylogenies was recovered as an undescribed lineage sister to A. anisolepis, not conspecific with any of the four A. crassulus lineages, including another Chiapan lineage. We also recovered the widely-used “A. sminthus” sample (which was previously hypothesized by McCranie and Kohler (2015) as representing an undescribed lineage more closely related to A. crassulus) as an undescribed lineage sister to A. morazani, and found additional mitochondrial lineages within A. heteropholidotus and A. rubribarbaris. Diversification within the group was estimated to have started in the early Miocene in the Chortis Highlands (supporting the results of Nicholson et al. 2017), with the Honduran population of A. crassulus diverging from the other three lineages approximately 13 MYA.

Figure 5 from Hofmann & Townsend, 2017. Chronogram showing results from divergence dating and ancestral area reconstruction analyses. PP shown when < 1.

Fig. 5 from Hofmann & Townsend, 2017: Chronogram showing results from divergence dating and ancestral area reconstruction analyses. PP shown when < 1.

Given the relatively deep divergence times within this group when compared with the apparent lack ecological and morphological diversification, we hypothesized that this subgroup represents a non-adaptive radiation, though extensive study is necessary to determine if these traits are as conserved as they appear. A taxonomic revision of the Chortis Highland population of Anolis crassulus is being finalized, but a great deal of work remains in order to improve our understanding of these highland anoles.

SICB 2018: Evo-Devo of Anole Digits


One more update from the SICB conference in San Francisco last week!

Across vertebrates, the ratio of lengths of the second and fourth digits of the hand are influenced by testosterone and estrogen. This could be of particular importance in species such as anoles, in which the fourth digits of the hindlimbs are extremely long and critically important in locomotion, but previous studies of the 2D:4D ratio in anoles have produced varying results. In the final poster session at SICB, undergraduate Griffin McNamara, working with Bonnie Kircher in Marty Cohn’s lab at the University of Florida, presented preliminary results from a study of cleared and stained brown anole (Anolis sagrei) hind feet. Griffin has big plans for continuing this work, so watch for future publications with these findings!

SICB2018: Density and Timing of Hatching Impact Survival and Growth in Anolis sagrei

Dan Warner (left) and Tim Mitchell (right) beside their poster on impacts of population density and time of hatching on survival and early life phenotypes of Anolis sagrei

Dan Warner (left) and Tim Mitchell (right) beside their poster on impacts of population density and time of hatching on survival and early life phenotypes of Anolis sagrei

Tim Mitchell a post-doctoral researcher at University of Minnesota with Emilie Snell-Rood presented his work from his prerious post doc in Dan Warner’s lab where he investigated the impacts of density and timing of hatching on the survival and growth of Anolis sagrei hatchings. Seeking to specifically address these questions:

How does investment in offspring size and number shift seasonally?

Does the timing of hatching influence survival or growth in the field?

And does adult density influence survival or growth of hatchlings in the field?

Adult anoles were brought into the lab on three different dates and breeding was split into three corresponding windows of time: Cohort 1 (February 23rd – April 27th), Cohort 2 (June 18th – July 30th), and Cohort 3 (September 5th – October 15th).  On experimental islands, adult densities were manipulated to create high and low lizard densities. Hatchlings from cohorts 1, 2, and 3 were released onto high and low adult density islands in June, August, and October, respectively, and researchers returned the following spring to recapture the marked lizards.

Breeding in the lab revealed a seasonal shift from producing more smaller offspring early to producing fewer larger offspring later in the season. Adult densities on the islands did not affect hatchling survival, but there was a substantial survival advantage to being an early-hatched lizard. Size and growth of hatchlings were influenced both by timing of hatching and the adult densities. So happy to catch up with my academic family and see the cool research they are doing!

Clipped Claws and Consequences for Anolis Adhesive Performance

Figure 1. Differences in claw clipping used in Bloch and Irschick (2005) and our study. (A) The entire claw was clipped after the distal end of the toe pad. (B) In our study, we partially clipped the distalmost portion of the claw.

Figure 1. Differences in claw clipping used in Bloch and Irschick (2005) and our study. (A) Bloch and Irschick (2005) clipped the entire claw after the distal end of the toe pad. (B) In our study, we partially clipped the distalmost portion of the claw.

Toe and claw clipping are common techniques used to identify individuals in mark and recapture studies, but their impacts on whole organism performance are unclear (Dunham et al., 1988). Anoles have not only developed subdigital adhesive toe pads to promote adhesion on relatively smooth substrates, but have also retained claws to enhance attachment to rough substrates (Irschick et al., 1996; Zani, 2000). Thus, clipping entire toes or claws may have drastic effects on the clinging ability of anoles or other adhesive pad-bearing lizards. In our recent article published in Acta Herpetologica, my co-authors and I investigated how partially removing the claws of brown anoles affects their adhesive performance.

Figure 2. Mean maximum clinging force of Anolis sagrei with intact and partially clipped claws. Overall, partial claw clipping had no significant effect on maximum clinging ability.

Figure 2. Mean maximum clinging force of Anolis sagrei with intact and partially clipped claws. Overall, partial claw clipping had no significant effect on maximum clinging ability.

Bloch and Irschick (2005) removed entire claws from Anolis carolinensis (Fig. 1A) and measured its impact on their clinging ability. Not surprisingly, claw removal resulted in a significant decrease in the clinging ability of A. carolinensis, likely a consequence of the severing of flexor tendons that are critical in adhesive toe pad engagement. In an effort to test this hypothesis and preserve these tendons, we used a motorized force sensor (Niewiarowski et al., 2008) to measure the maximum clinging ability of 19 Anolis sagrei before and after their claws were partially clipped (Fig. 1B).

Overall, we found that partial claw clipping did not significantly impact maximum clinging ability (Figure 2). This suggests that clipping the entire claws of anoles may indeed sever the flexor tendons crucial to toe pad engagement. Furthermore, we expected clinging ability to increase after partial claw clipping because claws should theoretically interfere with the contact the subdigital adhesive pads are capable of producing. However, this did not appear to be the case, suggesting that claws may not inhibit the engagement of subdigital pads or that morphological features and/or behavioral traits reduce the effect of this interaction.

Anolis sagrei

Anolis sagrei

Although permanent marking solutions would be most beneficial for mark and recapture studies, partial claw clipping may be a useful alternative for shorter-term studies because it does not appear to reduce adhesive performance on smooth substrates. Future work should further consider the interactions between subdigital adhesive toe pads and claws, and determine the possible ramifications for adhesion and adhesive locomotion, particularly on rough substrates. Be sure to check out our full article for more details!


Bloch, N., Irschick, D.J. (2005): Toe-clipping dramatically reduces clinging performance in a pad-bearing lizard (Anolis carolinensis). J. Herpetol. 39: 288-293.

Dunham, A.E., Morin, P.J., Wilbur, H.M. (1988): Methods for the study of reptile populations. In: Biology of the Reptilia, pp. 331-386. Gans, C. Huey, R.B., Eds, Alan R. Liss, Inc., New York.

Irschick, D.J., Austin, C.C., Petren, K., Fisher, R.N., Losos, J.B., Ellers, O. (1996): A comparative analysis of clinging ability among pad-bearing lizards. Biol. J. Linn. Soc. 59: 21-35.

Niewiarowski, P.H., Lopez, S., Ge, L., Hagan, E., Dhinojwala, A. (2008): Sticky gecko feet: the role of temperature and humidity. PLoS ONE 3: e2192.

Zani, P. (2000): The comparative evolution of lizard claw and toe morphology and clinging performance. J. Evol. Biol. 13: 316-325.


SICB 2018: Bigger Testes Don’t Produce Bigger Sperm


In the face of mate competition, sperm morphology can vary in a way that can enhance an individual’s chances of siring offspring of females. Studies in the past have attributed increased relative testis size as an approximate measure of an individual’s response to sperm competition. However, this does not take into account the internal architecture of the male testes that may contribute to changes in sperm morphology.

This was the focus of a poster presented by Hanna Hall titled “The evolution of sperm and testis morphology in Anolis lizards” in collaboration with Ariel Kahrl and Michelle Johnson. The authors sampled 2-20 individuals of different species of anoles in Puerto Rico and the Dominican Republic. They compared body size, sperm length ( 15 cells per individual), and the composition and size of various layers of the testis, by conducting a phylogenetic least squares regression on the average values obtained for each species.

The authors found that larger body size was associated with a larger testis size, which was in turn correlated with presence of large seminiferous tubules and a larger luminal area, where mature sperm are stored. Contrary to their expectation though, none of these aspects were associated with producing longer sperm. Further the Gonado-Somatic index (GSI), a common metric that serves as an indicator of relative testis size, was not correlated with any aspects of the internal testis architecture.

An interesting finding in this study was that species with a higher proportion of epithelial cells in the testis produced longer sperm. This result was surprising because larger number of epidermal cells may be associated with smaller spermatogonal cells, which would be predicted to form shorter sperm. The authors suggest that the correlation between lumen area and testis size may result because investment in sperm storage is more important, and that species may be producing large number of sperm which may be longer in length. Nevertheless, more data is needed to understand how changes in sperm morphology affect fertilization success and, further, under what circumstances does size and count of epithelial cells vary. The lack of correspondence of these results with that  shown in birds by Lupold et al. 2008 suggests that the mechanisms underlying sperm competition may be taxa or species-specific. We will be eyeing the Johnson Lab for more details on the same in the coming years.

SICB 2018: Role of Testosterone in Mediating Female Aggression in Anolis Lizards

An example of an aggressive display by a lizard. Photo Credits: Neil Losin Photography

An example of an aggressive display by a lizard. Photo Credits: Neil Losin Photography

Testosterone has long been though to influence male aggression behaviors. But can this same hormone influence aggressive behaviors in females too? Ellee Cook addressed this question in her talk titled “Investigating the potential for testosterone to mediate territorial aggression in female Anolis lizards.”

Ellee focused on studying a population of Anolis gundlachi in the forests of Puerto Rico. Ellee studied the response of focal females to a staged territorial intrusion by another female who was placed on a cage lid, and compared it to a scenario where she directly approached the lizard. She captured the focal females after twenty minutes of the trial and measured their size and took a blood sample to estimate the circulating levels of testosterone. Her prediction was that higher levels of aggression would be correlated with higher levels of testosterone.

Her data showed that females were indeed aggressive towards intruding females and had much higher displays of aggression in comparison to when they were presented only a lid or were directly approached. Surprisingly (or not so surprisingly), testosterone was not a significant predictor of female aggression. In fact, none of the hormonal measures corresponded to female aggression. This finding could have resulted for several reasons: A) the amount of testosterone detected in females was much lower than that found in males, making variation in testosterone  almost impossible to detect; B) High aggression may be caused by spontaneous spikes in testosterone that may be hard to detect; C) Female aggression may be governed by a completely different mechanism.

This study raises an important question about the relevance and drawbacks of existing paradigms which are male-centric and thus cloud our understanding when it comes to female behaviors. Cheers to more feminist paradigms in biology!

SICB 2018: Anoles and Undergrads: A New Kind of Science Lab

This post was written by Brittney Ivanov, research technician in the Johnson Lab.


PhD candidate, Abby Beatty, from Auburn University presented a poster entitled Integrating research into the classroom: causal effects of IGF1 and IGF2 on growth in the brown anole. The poster focused on an enhanced method of teaching science, particularly labs. The program, called C.U.R.E (Course-based Undergraduate Research Experience), allows students to experience teaching labs in a way that is more authentic and typical of the research experiences of graduate students. In most science labs, students are provided with different protocols and methods as well as a predetermined set of goals and results that explains how the experiment should turn out. The teaching method Abby proposed gives students the opportunity to learn from their failed attempts, before receiving the correct answers.

The course lasted for 2 semesters, consisted of undergraduate and graduate students, and began with a pre-survey that assessed student’s current knowledge as well as their ability in certain cognitive skills: analyzing, applying, creativity, evaluating, understanding, and memory. The students then chose a topic (related to Abby’s dissertation work) to be the focus of the labs. From this, they were able to develop methods and design their labs.

Specifically, the first semester class cloned and expressed IGF1 and IGF2 (insulin-like growth factors) using a bacterial vector. Similarly, the second semester class cloned IGFBP2. Abby then used these proteins to optimize methods for studying the growth rate of eggs and hatchling brown anoles. Hatchlings were monitored for 10 weeks following an injection with either IGF1, IGF2, or vehicle (NaCl + 15% Gelatin). Two trials were performed on the hatchlings and one on the eggs. In the first hatchling trial, IGF1 and IGF2 treatments had significantly higher death rates than control groups, but there was no association with body size. In the second trial, which used refined and updated methods, there was no significant effect on survival or body size, when compared to control groups. Finally, egg treatment did not correlate with survival or body size.

As the class completed each step in this process, they reviewed their work and if their methods were unsuccessful, discussed a better approach. Following completion of the course, the students received a post-survey assessing the same skills and knowledge as the pre-survey.

Abby found the class gained significantly in these skills, particularly receiving higher survey scores in the areas of creativity and understanding. She also found that the average score on the knowledge assessment was higher in the classes post-assessment survey than in the pre-assessment, indicating that the students may be gaining from this method of teaching. Control surveys from a class taught using a typical lab curriculum are not available, but there are plans to include this over the course of coming school semester.

These data, while still preliminary, highlight the benefit of implementing this kind of teaching strategy. When students are able to explore the process of asking and answering questions they generally become more engaged in their work and better prepared for more authentic research experiences.

SICB 2018: Local density of conspecifics affects sperm phenotypes in wild Anolis sagrei lizards

Theory predicts that males should invest more in ejaculate production when the likelihood of sperm competition is high, thereby increasing the chance of fertilization. However, ejaculates can be energetically costly, and increased investment into sperm production should only occur if there are fitness benefits associated with that increased investment. Growing experimental evidence suggests that sperm traits respond plastically to social environment. However, it is not known whether fine-scale spatial variation in the local density of male competitors or potential female mates corresponds to individual variation in ejaculate production.

Island population with capture records of males (blue) and female (red) anoles.

Island population with capture records of males (blue) and female (red) anoles.

Matt Kustra of the Cox lab examined a wild population to test the prediction that, as the risk of sperm competition increases (i.e., higher local density of male competitors), males will increase their total investment in their ejaculates (sperm count). He also tested for correlations between sperm morphology, specifically midpiece size and local density.

To do this, he and the Cox lab collected wild adults from an island population in Florida. They generated a map of each tree on the island using ArcGIS, then marked the location of males and females on this map. Using the kernel density function, they estimated the local density of individual males by taking into account all conspecific adults that were captured within a 5.8 m radius of an individual’s own capture location.

Matt found that length of the sperm midpiece increased with local density, whereas length of the sperm head and sperm count decreased with local density. Contrary to his predictions, he found that total investment in sperm count decreased with local density. This could be because males in high density environments have depleted their sperm stores because they have more opportunities to mate, or it could be because males are investing less per ejaculate if mating frequency is higher.

These findings indicate that fine-scale differences in local density within a wild population can affect sperm count and various sperm phenotypes. In the future, the Cox lab hopes to measure fitness in this populations to understand how sperm phenotypes shape individual reproductive success.

SICB 2018: Variation in metabolic rate among Anolis oculatus ecotypes on Dominica

Whereas in the Greater Antilles islands anoles evolved ecomorphs and live in communities with up to 11 species in sympatry, islands in the Lesser Antilles support only one or two species each. However, islands such as Dominica have populations of anoles that experience selective pressures resulting in different ecotypes.

Dominican Ecotypes

Figure from Thorpe et al. 2004

While Dominica is relatively small, the mountainous topology results in highly variable environmental conditions across the island with cool mountainous regions and warm coastal regions and thermal vents. The single endemic anole species present on the island, Anolis oculatus, exhibits four morphologically distinct ecotypes (Montane, Atlantic, North Caribbean and South Caribbean) and despite levels of gene flow between these ecotypes are high, adaptive differentiation in this system is maintained.

Photo by Aurélien Miralles

Photo by Aurélien Miralles

Tricia Neptune, a graduate student in the Watson lab, at Midwestern State University, explored whether these ecotypes also show any differences in metabolic rate (by measuring oxygen consumption) and its sensitivity to temperature (Q10) at ecologically-relevant temperatures.

Results show that size differences between ecotypes are reflected in their physiology with the south Caribbean ecotype exhibiting higher oxygen consumption and Q10 compared to the other three ecotypes. Tricia hypothesize that these differences in metabolism and temperature sensitivity are in part responsible for maintaining relaxed geographic segregation among ecotypes.

Tricia plans to incorporate data on sprint speed, bite force as well as investigate thermoregulation strategies in this species. It will also be interesting to see a comparative study between the A. oculatus ecotypes and the introduced Puerto Rican crested anole, A. cristatellus.

Figure from Thorpe et al. 2004

SICB 2018: Ecomorph Claws in Greater Antillean Anoles

The cover slide of Michael Yuan's talk at SICB 2018.

The cover slide of Michael Yuan’s talk at SICB 2018.

Convergent forms of anoles can be found across the Greater Antilles, with similar phenotypic and ecological morphs filling similar microhabitats from island to island.  Anole ecomorphs are in part defined by the extent of arboreality, as most species in the Greater Antilles spend a lot of time in trees.  Crandell et al. 2014 found arboreality to be associated with significant differences in claw characteristics in Costa Rica and Panama.  In Greater Antillean anoles, similar research into claw morphology has yet to investigate if this relationship holds across ecomorphs. Michael Yaun, a PhD student in the Wang lab at UC Berkeley, set out to investigate the patterns of variation of claw morphology in the Greater Antillean anoles.

Anolis barbouri is shown as an outlier in a PCA. The flattened claws of this ground-dwelling anole are illustrated in black to the right.

Anolis barbouri is shown as an outlier in a PCA. The flattened claws of this ground-dwelling anole are illustrated in black to the right.

Michael sampled 566 individuals, which included 55 species of anoles, all 6 ecomorphs, and another 8 species without any ecomorph designations.  His results suggest that perch height and diameter produced differential effects on claw characteristics.  Performance traits like toepad lamellae number and area were not correlated with claw height and length.  Michael’s study uncovered only one anole that conformed to previous research: Anolis barbouri, the only truly terrestrial species in the data set, possessing flattened claws.  Intriguingly, twig anoles have the most divergent claws, an inspiring result for future directions!

SICB 2018: Unraveling Natural and Human-Mediated Founder Events in Anolis carolinensis

Photo by Andrea Westmoreland

Photo by Andrea Westmoreland

Human-mediated range expansion is rapidly forming novel populations of anoles. The ancestry of these new populations typically traces back to a handful of individuals, and with repeated invasions the genetic history can be complex. These scenarios may be common in non-native populations of Anolis carolinensis, but what does the genetic history look like in such a system? In Sozos Michaelides’ talk at SICB 2018, he discussed his recently published findings.

Michaelides et al., 2017 tackled the question by inferring colonization history using mitochondrial haplotypes from Hawaiian Islands (Oahu, Hawaii, Maui, and Lanai) and some western Pacific islands (Guam, Palau, Saipan, Yap, and Rota). After genotyping 576 anoles, population genetic diversity and differentiation was assessed between native and non-native ranges. Results indicated geographically disparate haplotypes were identical (Hawaii to Brownsville, Texas), demonstrating that source populations may be from Texas or Louisiana. And a minimum of two introductions to Hawaii and Guam were uncovered, with subsequent within-population stepping-stone model colonization.

Overall, lower genetic diversity was found in non-native island populations as distance increased from the southeastern United States source population, and between the two archipelagos, genetic differentiation was high. Persistence of these non-native populations is not guaranteed because they are isolated, small in population size, and low in genetic diversity. It will be interesting to study the adaptive response of these introduced populations to stochastic climatic events!

SICB 2018: Insulin-Like Growth Factors and Anole Cells


The insulin signaling network has an essential role in growth, reproduction, and aging. Insulin-like growth factors, or IGFs, are important protein hormones within this network and are typically conserved across vertebrates. However, some proteins in the insulin signaling network have experienced selection in reptiles. Also, not a whole lot is known about the specific functions of components of this network within reptiles.

Amanda Clark, a PhD student in Dr. Tonia Schwartz‘s lab at Auburn University,  investigated the the function of purified IGFs on cell function for brown anoles (Anolis sagrei) and crested anoles (Anolis cristatellus). She had five different treatments for cell plates from both species: brown anole (BA) IGF-1, BA IGF-2, green anole IGF-1, a positive control, and a negative control. Cell proliferation was not different among all of the treatments, possibly due to incorrect protein folding or low concentrations of IGF. As expected, cell viability was also not affect by the IGFs. In the future, this experiment will be conducted again with increased sample size and an improved positive control.

SICB 2018: When the Lights Go Up in the City

Chris Thawley at a crossroads.

Chris Thawley at a crossroads.

Plants and animals across the globe are dealing with increasingly changing environments resulting from urbanization. One such habitat alteration is artificial light at night (ALAN) that may affect how animals acquire or use energy. Because brown anoles (Anolis sagrei) are common invaders of urban habitats, they make good models to examine the consequences associated with ALAN. Thus, Chris Thawley of Jason Kolbe’s lab at University of Rhode Island altered the level of ALAN on female brown anoles to examine how ALAN might affect morphology, reproduction, and stress.

If this sounds familiar, Chris talked about this work at the 2017 JMIH meeting, which caught Anole Annals press. To recap, Chris found that ALAN increased female growth, advanced the start of egg laying to earlier in the season, and increased the reproductive output of smaller females. However, he hypothesized that such beneficial effects would be countered by negative effects on other traits. Thus, Chris measured levels of the stress hormone corticosterone in the blood of females, hypothesizing that those exposed to ALAN would have higher stress. Although marginally non-significant, females actually tended to have lower corticosterone levels. Chris presented new data for this presentation showing that male corticosterone levels were unaffected by ALAN too, suggesting neither adult male nor female brown anoles have a stress response to artificial light.

Thus, it appears ALAN exposure over this 7-week study was beneficial for brown anole reproduction. However, Chris cautioned that there may be negative consequences on other traits such as immunity or HPA function. ALAN might also induce negative consequences for reproduction later in life, such as a reduced lifespan. I recommend keeping an eye on the Kolbe lab to find out!

SICB 2018: Moms Help Embryos Beat the Heat

Putter, Austin, and a real big tree they visited while travelling to the meeting.

Putter, Austin, and a real big tree they visited while travelling to the meeting.

The effect of urbanization on animals was the topic of many presentations at this year’s SICB meeting. One difference in the abiotic environment of urban areas is that they are often hotter than neighboring natural areas. Sarin “Putter” Tiatragul and colleagues (Josh Hall, Nathaniel Palik, and Dan Warner) at Auburn University are interested in whether urban environments might influence the nesting ecology and development of anoles. Thus, they set to the field to search for nest sites of the Puerto Rican Crested Anole (Anolis cristatellus).

Putter predicted females would choose warm, open-canopied nest sites at both urban and forested habitats, but that the availability of such locations would not be equal between sites. As predicted, randomly available areas in urban habitat had less tree cover and were warmer than randomly available locations in the forest. In the forest, females nested in locations that were similar to what was randomly available (no preference) in terms of distance to the nearest tree, canopy cover, and nest temperature. However, urban anoles nested in less open areas and closer to trees than what was randomly available in the urban habitat. This resulted in female-chosen nests sites being cooler than what was randomly available.

These findings suggest female anoles in forested areas are not choosing nest sites, probably because the forested habitat is homogenous and provides little variation to choose amongst. However, females in urban areas search out cooler microhabitats possibly to achieve favorable incubation conditions for their offspring. Putter also suggested these females may be simply nesting close to where they normally occur, which is close to trees. Either way, females are using the habitat differently in urban areas and such variation will likely have consequences for offspring during development.

SICB 2018: Revisiting the Fitch-Hillis Hypothesis in Mexican Anoles

A small sample of anole dewlap diversity. Image from Nicholson et al. (2007).

A small sample of anole dewlap diversity. Image from Nicholson et al. (2007).

Dewlaps are pretty dazzling, ranging in size, coloration, and sexual dimorphism substantially among the 400+ species of anole currently recognized. Levi Gray, a doctoral candidate at the University of New Mexico is fascinated by Anolis dewlaps, and has spent many years studying them. One of the classic hypotheses surrounding dewlap evolution in anoles is that its size follows a clinal pattern with environment (Fitch and Hillis 1984). In their formulation, Henry Fitch and David Hillis proposed that, due to a relatively short breeding season, anoles in more seasonal habitats have larger dewlaps than anoles in more aseasonal habitats. This hypothesis makes an explicit connection between the intensity of sexual selection and the size of a conspicuous ornament.

Levi set out to test the Fitch-Hillis hypothesis in 40 species of Mexican anoles distributed across environmental gradients, with some species found in aseaonal cloud forests and rainforests and others found in more seasonally dry habitats. Contrary to the Fitch-Hillis hypothesis, he found no relationship between seasonality and dewlap size in the Mexican anoles. He did detect a few clade effects: for example, a group of closely related western Mexican anoles all have large dewlaps. He then examined the Fitch-Hillis hypothesis within a single widespread species of anole, A. sericeus, to see if the pattern holds up within species, even if it doesn’t hold up among species. Again, he didn’t detect a pattern. Levi suspects that the relatively limited sampling of the original study might have led to a pattern that doesn’t hold up when a broader sampling within and among species is employed. It is possible that seasonality impacts a different aspect of the dewlap, such as coloration, but this remains untested. Levi’s results suggest that the processes impacting dewlap size might be complex, and promises more to come. Stay tuned!

Levi Gray presents his research on dewlap size evolution in Mexican anoles at SICB 2018 in San Francisco.

Levi Gray presents his research on dewlap size evolution in Mexican anoles at SICB 2018 in San Francisco.

SICB 2018: How Many Neurons Are in An Anole Brain?

Across species, bigger brains usually mean better cognition. But, this relationship rarely holds when considering individual differences within a species. Within species, the number of neurons in the brain may be a better proxy for cognitive ability than brain size. Further, the number of neurons may be independent of brain size.  But how to measure neuron number?


Levi Storks, a graduate student in Manuel Leal’s lab at the University of Missouri, set out to do just that. He adapted a protocol that has previously been used in mammals, birds, and crocodiles, but never before in lizards. In brief, he dissected the telencephalon, cerebellum, and other regions of the brain of an Anolis cristatellus and used the isotropic fractionator method to determine neuron number in each of the three. After homogenizing each tissue, he used a double-labeling technique with DAPI to stain each nucleus and neuronal nuclei antibody to stain each neuron, and used a hemocytometer to count the cells under magnification. Now that this protocol is working, look out for Levi’s future results on anole brain structure and cognition!