Author: mjohnson216 Page 2 of 5

Jeanel Georges with her poster at SICB.

The beautiful island of Dominica used to be home to only one anole (Anolis oculatus), but about 20 years ago, the Puerto Rican crested anole (Anolis cristatellus) showed up. Jeanel Georges, a graduate student in Matt Watson’s lab at Midwestern State University in Wichita Falls, Texas who is originally from Dominica, noticed that while A. oculatus occurs in all the ecological zones of the island, A. cristatellus is absent from the cooler, wetter uplands. With an international group of collaborators, Jeanel examined the thermal habitat use, sprint speed, and bite force of both species to determine what may limit the spread of A. cristatellus across the island.

At a lowland site where the two species co-occur, both species had higher body temperatures that the operative temperatures randomly available in the environment. In the much cooler upland site, A. oculatus had much higher body temperatures than the operative models, but these body temperatures were cooler than that species experiences in the lowland site. Jeanel also found that the two species had stronger bite forces and higher sprint speeds in the lowland site than A. oculatus had in the upland site. These data suggest that A. cristatellus and A. oculatus are partitioning the thermal environment of Dominica, and as climate change alters the temperatures available to lizards on the island, the interactions between these two species may change.

Austin Hulbert with his poster at SICB 2017.

This post was written by Brittney Ivanov, research technician in Michele Johnson’s lab at Trinity University.

Austin Hulbert, an undergraduate in Dan Warner’s lab at Auburn University, presented a poster on the behavior of brown anoles (Anolis sagrei) in a novel environment: a few very hot greenhouses in Auburn, Alabama. Brown anoles are an invasive species, most notably in Florida, but some populations have been found farther north in states including Louisiana, Alabama, Mississippi, and Georgia. As ectotherms migrate to higher latitudes, they often have to deal with different thermal environments and must alter their behaviors accordingly. Austin was interested in determining the activity patterns of a population of brown anoles inhabiting a group of greenhouses in Alabama.

During the summer he found that temperatures inside the greenhouses were consistently higher than those outside. Temperatures drastically increased each morning, up to peak temperatures between 11am and 3pm (on average, 45°C inside the greenhouse and 37°C outside). In the evenings, the temperatures again cooled. Austin surveyed the greenhouses and the surrounding areas for anoles during the morning, peak, and evening hours and determined the type of substrate each individual was using (i.e. brick or concrete, ground, metal, or wood). On average, brown anoles were more abundant inside the greenhouses than outside during the morning and peak times. He also found that more of the brown anoles perched on wooden substrate in the morning and evening. During peak hours more lizards perched on the ground. Because temperatures are often cooler closer to the ground, the lizards may be altering their behavior to deal with the extreme heat in the greenhouses during the hottest part of the day. While the visual survey focused on lizards perched in the open areas visible to the surveyor, there may have been individuals hiding under undisturbed objects as a means to keep cool during peak hours. In the future, Austin would like to compare the thermal tolerance of this group of brown anoles to those of populations in Florida to determine if inhabiting these greenhouses has resulted in adaptions to tolerate their more extreme temperatures.

Jerry Husak presenting at SICB 2017.

This post was co-written by Maria Jaramillo, an undergraduate in Michele Johnson’s lab at Trinity University.

A mother’s experience during gravidity may alter her offspring’s development, particularly through altering hormone levels in the yolk of her eggs. Stress hormones such as corticosterone (CORT) alter various aspects of offspring phenotype following in ovo exposure, and physical exercise elevates CORT in many vertebrates. In the work he presented at SICB, Jerry Husak and colleagues used exercise and food restriction to manipulate female Anolis carolinensis CORT, and to then determine whether the increased CORT was transferred to the females’ egg yolks.

Jerry assigned females to one of four treatments with different combinations of exercise and food restriction: 1) no exercise, regular diet; 2) no exercise, restricted diet; 3) exercise, regular diet; and 4) exercise, restricted diet.  He found that maternal exercise increased maternal CORT (as expected), but surprisingly did not result in higher CORT in the eggs. Further, diet restriction did not affect maternal CORT, but moms with restricted diets laid eggs with reduced CORT.

This study suggests that anole mothers may manipulate the environments of their eggs in ways we don’t yet understand – the mechanisms by which CORT is transferred to eggs is an area ripe for future study!

Sukalia Miller with her poster at SICB.

This post was written by Miguel Angel Webber, an undergraduate in Michele Johnson’s lab at Trinity University.

An animal’s position in a social hierarchy can influence many aspects of its behavior. In the green anole (Anolis carolinensis), a growing body of literature indicates that dominant males behave differently than subordinate males, and that these behavioral differences may be present even prior to the establishment of a dominance hierarchy. Sukalia Miller, a recent undergraduate in Walt Wilczynski’s lab at Georgia State University, designed an experiment to determine whether subordinate and dominant males differed in their rates of courtship, aggression, and exploratory behavior.

After taking baseline measures of behavior, size-matched green anoles were paired and allowed to establish dominance relationships over the course of six days. Following this pairing, each lizard was then tested again to determine post-pairing measures of behavior. Miller found that subordinate males did not differ from dominant males in their rates of aggression (as simulated in a mirror test) or courtship (tested by placing a female in the habitat) prior to pairing, but that bouts of aggression and courtship practically disappeared in the subordinate group after pairing. Additionally, Miller found that there was a trend in the dominant lizards, such that individuals with higher rates of pre-pairing aggression had higher rates of aggression post-pairing. However, no such relationship was found between pre- and post-pairing rates of courtship in either the dominant or subordinate group, and no Miller observed no differences in exploratory behavior between either group of lizards.

These results suggest that the influence of social status on behavior may be limited to social behaviors in green anoles, and furthermore, that these behavioral differences may not be detectable prior to the establishment of a dominant-subordinate hierarchy.

This post was written by Miguel Angel Webber, an undergraduate in Michele Johnson’s lab at Trinity University.

Samantha Adams presenting at SICB.

The parietal eye, a photosensitive organ located on top of lizards’ heads, has long been thought to play an important role in regulating lizards’ circadian rhythm and body temperature. The eye detects UVB rays, mediating the release of melatonin from the pineal gland and evoking a behavioral response. Samantha Adams, an undergraduate at Marosh Furimsky’s lab at Westminster College, PA, conducted a study on bearded dragons (Pogona vitticeps) and green anoles (Anolis carolinensis) to examine the effects of masking their parietal eye on their thermoregulatory behavior. Adams took individuals from each species and set up a testing arena, placing a UV-B light-only source and an infrared heat-only source on opposite sides. She then tracked the amount of time each lizard spent under either lamp, doing so before masking the parietal eye, while the eye was painted with black non-toxic paint, and again after uncovering it.

Adams found that bearded dragons rely heavily on the eye for thermoregulation – while lizards ordinarily spend less than 20% of their time basking underneath the heat source, lizards with their parietal eye masked spent the vast majority of their time under the heat lamp. Additionally, all of her bearded dragons experienced erratic locomotion in the day post-masking, running so frequently from side to side of the cage that she had trouble characterizing the lizard’s lamp preference. Once the black paint was removed, lizards took one to two weeks to resume ordinary behavioral patterns. However, she found that the green anoles in her study seemed unaffected by the experimental manipulations; lamp preference was unchanged by covering the parietal eye, and anoles spent roughly 25% of their time under the heat lamp in both the control and experimental treatments. The anoles displayed none of the erratic locomotor patterns Adams found in the bearded dragons, and other than a qualitative account of more time spent being brown, the lizards seemed unperturbed by the black paint on their parietal eye.

Adams’ results shine a new light on the parietal eye, long thought to be a structure essential to all lizards that possess it, as a potentially vestigial structure in green anoles. Future work is necessary to understand any other roles the eye could serve in anoles, but the stark difference with bearded dragons in this study helps illuminate the wild evolutionary path of our favorite lizards.