It’s been a long time since we’ve updated our Meet the Anole Scientists section of Anole Annals, so we’re going to do that now! The last time we did this was back in 2020, so we figured it was about time to put some new faces up on our website. You can see the Meet the Scientists section of our webpage here.

If you are interested in being featured, please fill out the attached Google form here. Thank you for your participation, and we look forward to getting your profile up on the website shortly!

Mr. Wayne Wang from Tulane University.

It’s no surprise that reproductive traits are important for the survival and fitness of species- particularly in the face of changing environments. What I learned from Mr. Wayne Wang’s talk at SICB 2022, though, was that male fertility is often more heat-sensitive than female fertility and even adult thermal tolerance! Wayne is a 3^rd year Ph.D. student at Tulane University under Dr. Alex Gunderson and at SICB this year, he discussed his preliminary results on Cuban brown anole (Anolis sagrei) sperm thermal tolerance and mobility.

In some species, the temperature associated with infertility in males is often a better determinant of population distribution than adult thermal tolerance. Additionally, sperm are under strong selection because only few make the journey to fertilize an egg (which means that they are also one of the most highly diverse cell types). Mr. Wang noticed that in the literature, there is a large focus on sperm morphology, rather than physiological traits like mobility or speed. In his talk, he sought to 1) test thermal tolerance of sperm, 2) test repeatability of thermal tolerance, and 3) identify any correlations between sperm and adult thermal tolerance in A. sagrei. He began by rounding up some lizards and copulating them until they ejaculated sperm, which he states is a lot easier process than one might imagine. Sperm were diluted and incubated at various temperatures until videos were recorded to measure sperm motility.

Mr. Wang found that A. sagrei sperm motility did not differ much between 33°C and 41°C; however, at approximately 43°C, there is a steady decline where approaching 48-50°C, none survive. In fact, 50% of sperm stop moving at about 43°C. This experiment was repeated with the same group of lizards during a second week following a seven-day acclimation period. Similar patterns were observed and during week 2, more individuals had a higher percentage of sperm motility. Lastly, no correlations between sperm and adult thermal tolerance were identified–Mr. Wang speculates that this might be because these traits are not linked or his sample size did not allow for enough resolution.

Be sure to check out Wayne Wang’s awesome talk here!

This site has all kinds of useful information! Here’s the site’s story (“about us”):

Our Story

Esri created the Caribbean GeoPortal Program to support an open mapping community across the Caribbean. As a global company, Esri’s distributors and employees have been working across the countries and territories in the Caribbean for many years.

The Caribbean GeoPortal is a comprehensive cloud-based platform that is focused on advancing three main goals for the region:

• increasing the capacity of organizations in the region through GIS training and education
• improving collaboration and information sharing among organizations in the region
• providing organizations in the region with the necessary GIS capabilities to support their work

The Society for Integrative and Comparative Biology (SICB) conference is a national gem for highlighting research from biologists across the country. This year, over a thousand researchers shared their work in Phoenix, AZ and on online platforms for the 2022 SICB conference. Fourth-year Ph.D. Candidate, Annelise Blanchette, from Tulane University in New Orleans, LA under Drs. Alex Gunderson and Jordan Karubian was one of these presenters. Like Phoenix, New Orleans is a bustling city with everything from high-rise skyscrapers soaking in the Louisiana sun to paved neighborhoods polluted with anthropogenic waste (e.g., Mardi Gras beads). Ms. Blanchette discussed this idea of pollution, particularly the contaminant lead, at SICB 2022 and wanted to know more about the influence of lead on physiological performance of her study species, the Cuban brown anole (Anolis sagrei).

Ms. Annelise Blanchette and her study organism, the brown anole (Anolis sagrei).

Ms. Blanchette’s previous work showed that anoles from areas in New Orleans with high soil lead levels had over 10X the toxicity threshold of lead (in comparison to birds and mammals) in their bloodstreams. She wanted to know how these lizards were influenced physiologically by lead exposure and how that translates to physiological performance by measuring sprint speeds and balancing ability of anoles from these regions. She predicted that there would be an overall negative effect of high bloodstream lead levels and that lizards from these high exposure areas would 1) not be as fast as their counterparts in terms of sprint speed, and 2) have decreased balance, measured by counting the number of times they slipped on a wooden beam.

Measuring balance of anoles by counting number of times individuals slip from the wooden beam.

From her results, she found that there is no correlation between lead exposure and sprint speeds; however, there is a negative effect of lead on balance that may be sex-dependent. In fact, male anoles exposed to low levels of lead had fewer slips (i.e., better balance) than males exposed to high levels of lead. She states “It’s surprising given the incredibly high levels of lead in their bloodstream that the brown anole is coping with the exposure so well.” This work is particularly fascinating because it begins to uncover ways urbanization can influence wildlife in nearby regions though pollution of heavy metals. “… if we don’t find an obvious or devastating affect behaviorally or cognitively in the brown anole, perhaps we’ll find that they have adapted and are less resistant to lead’s detrimental effects – which would be so cool!” Ms. Blanchette says. She hopes that next year, like many other virtual SICB members, she will be able to present her work in person!

You can check out Annelise’s talk from SICB 2022 here! Follow her on Twitter @basicbiologist!

The Society for Integrative and Comparative Biology annual conference is happening next week, January 3-8 2022! With a return to in-person events, we are aiming to highlight the breadth of research talks and posters on anoles given by all the amazing junior researchers at the conference!

This post is a call-to-arms: we can’t cover all the presentations without your help! We are looking for interested folks attending the conference that can help the Annals by contributing blog posts featuring these researchers and their anoles. Folks that elected to do the virtual SICB+ option instead of attending in-person are also encouraged to get involved. If you’re interested, please contact Anthony for any additional details or information.

Below is a list of anole presentations happening at SICB 2022- please reach out if I missed any of any of these peaks both your scientific and blogging interests!

Anolis cristatellus (pictured; Wikimedia Commons) continues to prove itself as a model organism for examining thermal biology evolution, particularly in a comparative context of forest versus city-dwelling populations. Recent research by Campbell-Staton et al. (2021) aims to uncover how differential gene expression modulates adaptive and maladaptive plasticity in these populations.

In a recently published study, Shane Campbell-Staton and company continue their comparative investigation of urban-forest anole thermal biology. Employing a combination of wild-caught and common-garden-reared urban and forest populations of Anolis cristatellus, Campbell-Staton et al. (2021) tease apart the role of selection in mediating adaptive and maladaptive thermal tolerance plasticity using a fine-toothed transcriptomic comb.

New literature alert!

Selection on adaptive and maladaptive gene expression plasticity during thermal adaptation to urban heat islands

In Nature Communications

Campbell-Staton, Velotta, and Winchell

Abstract

Examples of embryos with normal and abnormal craniofacial development

Embryos are not just little organisms encapsulated within their eggs. Embryonic development is dynamic; the embryo transitions from one to a few undifferentiated cells to a stage where the various parts like arms, legs, and faces become apparent to a form that resembles the species that will eventually emerge. A panoply of signaling events and rapid rates of cell division are all tightly choreographed to make sure that development proceeds in a predictable, species-specific fashion.

But this dynamism of development also makes the embryo susceptible to environmental perturbation. Heat, chemical exposure, and pathogens can all disrupt normal embryonic development, sending the embryo down paths that may lead to fatality or reduced fitness. In our recently published study, my colleagues, students, and I demonstrate that heat stress, paralleling what will likely be experienced during the 21st century, can induce structural malformations to the brain and face of lizard embryos.

In 2014 and 2015 I was a post-doc in the Cohn Lab at the University of Florida. At the time, I had been dissecting and observing anole embryos for approximately 14 years. Throughout those 14 years I had observed only a handful of malformed embryos, maybe on the order of 10-20 embryos after collecting thousands of embryos from numerous anole species. Yet, in the summers of 2014 and 2015, while working alongside then graduate student Bonnie Kircher, I collected more malformed Anolis sagrei embryos than I had in all of my previous years. I certainly didn’t realize it in the moment as malformed embryos were still relatively rare compared to the total number of embryos we were collecting. But, by the end of my time in Florida the number jumped out at me. Sometimes the rate of development seemed to depart from the normal sequence of development. Other times the embryo was clearly not well and would likely not survive to hatching. Even as other projects accelerated, my interest in these malformed embryos remained piqued.  When I began my faculty position Loyola University Chicago, I decided to invest the lab’s time and resources into determining whether this pattern was real or just a chance observation.

In spite of other options­–unique genetic mutation running rampant in Gainesville populations of brown anoles seems highly unlikely–I decided to investigate the effects of heat stress on embryonic development. The effects of global warming had been widely discussed as a threat to ecotherm populations and anoles have been at the center of both field and lab observations since the outset. A number of studies have also shown reduced hatching success from lizards incubated at relatively high temperatures. Relating this back to my observations in Florida, it also occurred to me that Bonnie and I used a different collection strategy for our breeding colony those years; we would regularly replenish or add to the colony from field-caught lizards throughout the summer. This raised the possibility that the embryos developing within the gravid females were exposed to the environmental heat stress before being deposited into our waiting hands. Luckily, brown anoles are prolific egg producers, providing my lab with the ability to test whether heat stress induces embryonic malformations under different incubation regimes.

Embryos incubated under conditions reflecting those observed in shady nest sites exhibit malformations in only one to two embryos out of every 100 live embryos. These nest sites tend to be relatively stable in temperature, rarely rising about 30 degrees Celsius. However, embryonic heat stress induces malformations in 10-30% of embryos exposed to incubation conditions that parallel nest sites that would be located in sunny locations. These putative nest sites reach temperatures above 36 degrees Celsius, the critical thermal temperature for the embryos, for up to eight hours per days. The malformations we observed were not evenly spread across the body. Instead, we saw the greatest concentration in the brain and face of the developing lizards. Most malformations included a change in facial proportion, from subtle changes in facial length to pronounced brachycephaly and/or clefting. In one case, the entire face and forebrain were ablated in the embryo! When it comes to the induction of structural malformations, the most sensitive period of development is around oviposition, including the time that the egg is still within the female. Although we do not yet know how many of these embryos would successfully hatch, our experiments do raise concerns about the long-term impacts of global warming on ectotherm development.

Examples of extreme, but rare malformations observed in eggs reared at elevated temperatures.

The consistent pattern of thermal-induced neural and facial anomalies made us think that there may be a common underlying cause of these changes, leading us to create and test a new model of embryonic thermal stress. Based on our understanding of amniote craniofacial development, we predicted that disruption to Hedgehog signaling, one of the earliest signaling pathways needed for facial development, could create the full spectrum of observed malformations. After measuring processes up and downstream of Hedgehog signaling (e.g., cell death and signaling within the presumptive facial cells respectively), it does, in fact, appear that Hedgehog signaling is disrupted in the face of embryos experiencing thermal stress. Depending on the degree of response by a particular embryo, everything from normal to extremely malformed embryo could be induced. At this time, it appears that our model holds for brown anoles and may be applicable in species far beyond anoles and lizards.

In our proposed model, heat stress affects Hedgehog signaling, causing a disruption to normal facial morphogenesis.

There remains much to learn about normal and abnormal facial development in lizards. We do not yet know what other signaling pathways are equally disrupted during thermal stress or whether there are endogenous buffering mechanisms that help to maintain normal development in the face of external stress. Perhaps one of the most important discussions that needs to occur is how we study rare events. These events could be uncommon, but extreme heat events that exceed the “normal” conditions typically observed in the wild. These are increasing in regularity and may have significant impacts on ectotherms later in the 21^st century. Alternatively, the rare events could be the emergence of malformed embryos which occur in only a fraction of individuals, even when the average phenotype is not dramatically altered. For species such as the brown anole, this may not be alarming. But for species with relatively few viable hatchings each season, embryonic heat stress could have dramatic impacts on their long-term viability. These developmental perspectives  are needed to fully understand the ways that global change will affect the lives and longevity of lizards and other ectotherms.

Embryos are impacted by a range of challenges associated with anthropogenic change. See more in Sanger 2021, Integrative developmental biology in the age of anthropogenic change

An illustration from Gosse (1851) depicting Jamaica’s crown-giant, Anolis garmani (note that Gosse used the old name, “Dactyloa Edwardsii”), adjacent to a West Indian boid (Chilabothrus).

Jamaica’s six endemic Anolis species–A. garmani, A. reconditus, A. valencienni, A. lineatopus, A. grahami, and A. opalinus–have long captured the fascination of Caribbean naturalists. And how could they not? Although only six, these lizards are among the Caribbean’s most eye-grabbing. Take it from Phillip Henry Gosse, who recounted his experience catching one of these six species using a twine lasso in A Naturalist’s Sojourn in Jamaica (1851):

“The mode in which I formed an acquaintance with the species may be worthy of being related. One day in February, having ascended the ridge with a companion, my attention was arrested by a Lizard about a foot long, and of a lively green colour, on the trunk of a small tree, head downward, intently watching our motions as we stood near. My young friend suggested the possibility of capturing it by slipping a noose over its head, while its attention was engaged by whistling. I laughingly proceeded to try the spell; and having made a noose of small twine, which I tied to the end of a switch, I gently walked towards him, whistling a lively tune. To my astonishment he allowed me to slip the noose over his head, merely glancing his bright eye at the string as it passed. I jerked the switch; the music ceased; and the green-coated forester was sprawling in the air, dangling, greatly to his annoyance, at the end of my string. He was very savage, biting at every thing near; presently his colour began to change from green to blackish, till it was of an uniform bluish black with darker bands on the body, and a brownish black on the tail: the only trace of green.”

Since Gosse’s work on West Indian reptiles (including formal designation of the Jamaican anole radiation as Placopsis), much has changed in our understanding of Jamaica’s Anolis diversity and evolution. In 2002, Todd Jackman and colleagues published a study aiming to estimate the phylogenetic relationships among Jamaica’s anoles.

The authors found support for the following topology (Jackman et al. 2002; Fig. 7): A. lineaotopus and A. reconditus form a clade that is sister to the remaining Jamaican anoles, followed by A. valencienni, A. garmani, and, ultimately, A. grahami + A. opalinus. Jackman et al. would continue in the same paper to discuss phylogeography and intraspecific divergences. Notably, a single A. opalinus from Hardwar Gap (Blue Mountains) appeared to be more closely allied to A. valencienni than to other sampled A. opalinus individuals. This diverse array of mitochondrial haplotypes recovered from A. opalinus then raises the question, does the history of Anolis on Jamaica involve hybridization, or is it merely a result of incomplete lineage sorting we may expect from a rapid adaptive radiation?

Nearly twenty years went by without an answer. Was the phylogenetic hypothesis posited by Jackman et al. correct? What’s going on with A. opalinus? Separately, in the two decades since the work by Jackman and colleagues, a revolution has occurred in phylogenetic biology. In the study of phylogeny, if introgression (e.g., ancient mitochondrial capture as a result of hybridization) has played a role in shaping the evolutionary history of the relevant group, it’s important that we test if such events have occurred, and subsequently be able to disentangle and ultimately account for them in our phylogenetic estimations. Failure to do so can lead to misleading topologies, inaccurate reconstructions of evolutionary histories and parameter estimates, as well as shortcomings in accurately describing and recognizing biodiversity.

Luckily, resolution to this issue has been afforded by several folks (Claudia Solís-Lemus and Cécile Ané, to name just two) who have developed statistical methods to detect and account for both incomplete lineage sorting (ILS) and reticulate patterns of evolution (introgression). So, how does this relate to those oh-so-cool Jamaican anoles? This is where Myers et al. (2021) come in.

In a new study in the Spotlight section of Systematic Biology, Myers and colleagues re-open the investigation into Jamaican Anolis phylogeny using the aforementioned suite of novel methods. For those in attendance at the Joint Meeting of Herpetologists and Ichthyologists in 2018, the early stages of this work were presented by students conducting research at the American Museum of Natural History, previously featured on Anole Annals. Using genotyping-by-sequencing (an approach that has been applied elsewhere in Anolis research), the authors generate swaths of SNP data from the nuclear genome. To be exact, the total dataset comprised 257,317 base pairs (just over 2,900 loci). Restriction-site-associated approaches (i.e., RAD-Seq) to sequencing DNA have made it feasible to capture large, representative samples of the nuclear genome at low cost.

Armed with data from both the nuclear and mitochondrial genomes, Myers et al. (2021) found dramatically different relationships and evolutionary histories among species between the two sources. Figure 3 demonstrates this disparity well, and further hammers home the general dangers of violating model assumptions in phylogenetic inference (in this case, the multi-species coalescent [MSC] model, which assumes a lack of gene flow among sampled taxa).

First, when using solely the mtDNA data in a MSC framework, the authors find A. opalinus from the Blue Mountains to be polyphyletic, a result concordant with the inference of Jackman et al. (2002). Specifically, one A. opalinus lineage (Blue Mountains) is sister to A. valencienni, whereas the other A. opalinus lineage is sister to A. grahami. Notably, the time calibrated mtDNA gene-tree suggests the two A. opalinus mtDNA genomes are more than 30 million years divergent!

The authors then infer a species tree using the GBS data in an MSC framework (one that assumes gene-tree species-tree discordance can be attributed to incomplete lineage sorting and accounts for such). With this tree, the two A. opalinus lineages form a clade sister to A. grahami and A. garmani. Finally, with SnaQ (a modeling program developed by Solís-Lemus and colleagues to infer reticulation events across a tree), the authors recovered an identical topology to the nuclear DNA based species-tree, but with high support for a single introgression event (and hence, reticulate evolution) between A. opalinus and A. grahami. Using simulations, Myers and colleagues provide evidence against ILS as the causative agent for gene-tree species-tree discordance, favoring hybridization as the culprit.

I won’t spoil the Discussion, but much of Jamaican Anolis evolution remains open-ended (including the role of adaptive introgression in shaping Anolis communities). It’s probably safe to say Gosse wasn’t pondering the possibility of adaptive introgression in shaping Jamaican Anolis phylogeny. However, resolution of the outstanding questions identified by Myers et al. (2021) will come primarily through Gosse’s philosophy–getting out in the field, catching lizards, and getting a more-fine scale, phylogeographic picture of the variation over space and time in Jamaican Anolis.

I thank Ed Myers and Kevin de Queiroz for feedback on this blog post.

Literature Cited:

Jackman, T. R., Irschick, D. J., De Queiroz, K., Losos, J. B., & Larson, A. 2002. Molecular phylogenetic perspective on evolution of lizards of the Anolis grahami series. Journal of Experimental Zoology 294(1) 1-16.

New literature alert!

Interspecific Gene Flow and Mitochondrial Genome Capture During the Radiation of Jamaican Anolis Lizards (Squamata; Iguanidae)

In Systematic Biology

Myers, Mulcahy, Falk, Johnson, Carbi, de Queiroz

Gene flow and reticulation are increasingly recognized as important processes in the diversification of many taxonomic groups. With the increasing ease of collecting genomic data and the development of multispecies coalescent network approaches, such reticulations can be accounted for when inferring phylogeny and diversification. Caribbean Anolis lizards are a classic example of an adaptive radiation in which species have independently radiated on the islands of the Greater Antilles into the same ecomorph classes. Within the Jamaican radiation at least one species, A. opalinus, has been documented to be polyphyletic in its mitochondrial DNA, which could be the result of an ancient reticulation event or incomplete lineage sorting. Here we generate mtDNA and genotyping-by-sequencing (GBS) data and implement gene-tree, species-tree, and multispecies coalescent network methods to infer the diversification of this group. Our mtDNA gene-tree recovers the same relationships previously inferred for this group, which is strikingly different from the species-tree inferred from our GBS data. Posterior predictive simulations suggest that our genomic data violate commonly adopted assumptions of the multispecies coalescent model, so we use network approaches to infer phylogenetic relationships. The inferred network topology contains a reticulation event but does not explain the mtDNA polyphyly observed in this group, however coalescent simulations suggest that the observed mtDNA topology is likely the result of past introgression. How common a signature of gene flow and reticulation is across the radiation of Anolis is unknown; however, the reticulation events that we demonstrate here may have allowed for adaptive evolution, as has been suggested in other, more recent adaptive radiations.