Tag: thermal physiology

Evolution 2016: Polar Vortex Revisited

On June 23, 2016

Shane Campbell-Staton giving his talk at Evolution 2016

We’ve heard about the effects of polar vortexes here on Anole Annals before. The infamous 2013/2014 event brought record-breaking snow and low temperatures to the Southern U.S., leaving people and animals both a little chilled. This created the perfect opportunity for Shane Campbell-Staton to investigate the effects of such extreme events on thermal tolerance of the native Carolina Anole, Anolis carolinensis. Shane also spoke about this at SICB earlier this year, and AA contributor Martha Muñoz covered the talk pretty thoroughly here on Anole Annals. Nevertheless, I’ll summarize some key points here in case you missed it.

An unlucky lizard during the polar vortex snow storms in the South.

Shane got lucky in the sense that he had measured thermal tolerance in August 2013 for populations affected by the polar vortex, 5 months before the event. Typically, the cold arctic air is tightly constrained around the North pole, but periodically the boundaries weaken and the cool air expands southward. These events are not regular, so Shane had no idea one was coming that winter or that it would extend so far south. It was serendipitous that his study populations, 3 in Texas and 1 in Oklahoma, were impacted by the extreme weather event. This species, particularly in the Southern portion of its range, is not used to low temperatures and reports came in of anoles dying off during the storm.

Air temperatures for January 5-7, 2014, compared to the 1981-2010 average. Map by NOAA Climate.gov

So Shane returned in August of 2014 and sampled again, curious as to how this cold impacted thermal tolerance. He found that tolerance to low temperatures, measured as critical thermal minimum (CTmin), was lower in some populations after the event! Even more, the difference was greatest in the Southernmost population (Brownsville, Texas). Shane returned again in the fall of 2014 to see if this effect persisted or if it was simply a plastic response to the event. He found that the populations sampled in 2014, and presumably their offspring, still had lower critical thermal minimums. This result suggests that the extreme cold weather had caused an evolutionary shift in cold tolerance via natural selection: only the animals that could tolerate the cold temperatures survived and passed on their cold-tolerance genes. Shane went on to conduct a common garden study to verify that the trait was not simply a plastic response. He found that the lower CTmin persisted in lab-reared animals: strong evidence that these shifts had a genetic basis.

Lastly, Shane looked at the functional genomics of cold tolerance. Using liver tissues to obtain transcriptomes (representing expressed genes), he found several gene modules associated with thermal tolerance including some associated with respiratory electron transport chain, lipid metabolism, carbohydrate metabolism, and angiogenesis/blood coagulation. He also found that the gene expression patterns in the Southern populations affected by the storm resembled the Northern populations that more regularly experience cool temperatures, indicating a common genetically based adaptive response across populations.

Evolution 2016: It’s Getting Cold in Here!

By Kristin Winchell

On June 19, 2016

In New Research

Tamara Fetters with her poster at Evolution 2016

Tamara Fetters, from the McGlothlin lab at Virginia Tech, reported on her ongoing work on thermal physiology in Anolis sagrei during the first poster session here at Evolution 2016 in Austin, Texas. Tamara looked at thermal tolerance and sprinting abilities at different temperatures and how that related to the latitude of the population. Specifically, she asked if lower temperatures regularly experienced by the Northern populations influence cold tolerance and performance at those temperatures. She expected that Anolis sagrei, native to Cuba and the Bahamas and introduced into the Southern U.S., would show signs of adaptation to its new, colder home in the more Northern mainland populations compared to the native range island populations in the South.

Tamara’s poster focused on two main experiments. In the first she calculated thermal tolerance to cold temperatures using a classic critical thermal minimum (CTmin) setup: with an ice bath she slowly lowered the body temperature of each animal until it was unable to right itself. This method approximates the minimum temperatures that the animals can handle in the wild. She found a clear trend showing a decrease in the minimum temperature tolerated as latitude increased. In short, Northern populations could handle the cold and Southern populations could not.

In the second experiment, Tamara acclimated the lizards to 6 temperatures ranging from 12-41 °C before running them up a track to calculate sprint speed. Tamara used an impressive 25-50 animals from each of 5 populations! She calculated sprint speed from the high-speed video she took using the program Kinovea. Tamara found that across all temperatures the most Southern population ran the slowest while the most Northern population ran the fastest, with the differences remaining fairly constant.

So what’s next for Tamara? She is planning on rearing animals in a common garden setup with some animals in hot temperatures with low variability between day and night (mimicking the native range, Southern habitats) and some animals in cool temperatures with high variability between day and night (as is experienced in the Northern habitats). She hopes that these studies will help her understand the genetic basis of this thermal tolerance and the extent of plasticity in thermal adaptation.

One last note – Tamara wanted to thank Anole Annals for helping her determine her study locations. She was able to determine which areas were likely to have Anolis sagrei and how far North they have spread because of Anole Annals posts (like this one) and comments.

Click to view a bigger version of Tamara’s poster

Registro de Copula de Anolis huilae

By DAVID ALFONSO BEJARANO-BONILLA

On October 6, 2014

In Anole Photographs, Natural History Observations, New Research

Copula de Anolis huilae.

En el marco de mi tesis de maestría sobre la Ecofisiología térmica de Anolis huilae tuve la oportunidad de observar, creería que sería el primer registro, una pareja de ésta especie copulando en el tronco de un árbol. Evento que lo considero relevante por la falta de información acerca de ésta especie.

El estudio lo estoy desarrollando en el Corregimiento de Juntas, Ibagué (Colombia). Mi objetivo es conocer aspectos de la fisiología térmica de A. huilae y relacionarla con las temperaturas ambientales y microambietales de su hábitat. Para la colecta de datos me estoy apoyando con una cámara termográfica infrarroja (metodología no invasiva) y modelos de cobre con data loggers insertos en ellos.

Imagen termográfica de copula de Anolis huilae.

En una primera etapa del estudio estoy averiguando si A. huilae es una especie heliotérmica o tigmotérmica; como también, si es termoconformadora activa o termoconformadora pasiva. Datos que próximamente los compartiré.

Observaciones comportamentales, no registradas, ayudarán a conocer más aspectos de la biología y ecología de ésta especie, de la que aún falta mucho por descubrir. Así mismo, he observado en esta localidad la simpatría con otro anolis, Anolis antonii.

*****

English translation via the internet:

Record of Copulation of Anolis Huilae

In the framework of my master’s thesis on the thermal ecophysiology of Anolis huilae, I had the opportunity to observe, you would not believe that would be the first record, a couple of this species copulating in the trunk of a tree. Event that is considered relevant by the lack of information about this species.

The study, I am developing in the Corregimiento of seals, Ibagué (Colombia). My goal is to understand aspects of the thermal physiology of A. huilae and relate it to the ambient temperatures and microenvironments of its habitat. For the collection of data I am supporting with a infrared thermal imager (non-invasive methods) and copper models with data loggers inserts in them.

In the first stage of the study, I am enquiring whether A. huilae thermoregulation is a species or is thigmothermic; also, whether it is an active or passive thermoregulator. I will share the data soon.

Behavioral observations, unregistered, help you learn more aspects of the biology and ecology of this species, which still lack much to discover. Also, I’ve seen in this locality the sympatry with another anole, Anolis antonii.