Tag: SICB2020

SICB 2020: Artificial Light Keeps Green Anoles Hungry!

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On January 8, 2020

In All Posts, New Research

There are so many great anole talks at SICB 2020, I’d be remiss if I didn’t take this opportunity to shed some light on some of our fantastic undergraduate researchers, who turned out in force to Austin this year! As I’m sure Dr. Kristin Winchell will tell you, anole lizards make awesome model organisms for studying the effects of city life and urbanization on wildlife.

Cities can be dangerous though. A lot of different urban environments will present wildlife that have not lived in cities with numerous pressures they might not have faced before, such as different surfaces and substrates on which to run, different temperatures, and even new predators. One of the relatively new pressures that goes along with city life is light at night, and artificial light to boot. If you’ve ever been too disturbed by light during the moonlight hours to sleep and rest, imagine how small lizards feel!

To address the effects of this pressure on green anoles (Anolis carolinensis), Michelle D’Alessandro, an undergraduate student at the University of Scranton working in the lab of Dr. Chris Howey, measured the effects of artificial light at night (I’m just going to call it ALAN) They exposed anoles to ALAN and described the effects of artificial light on metabolism in green anoles. Initially, they did not find any differences between metabolic rates when lizards were exposed to ALAN, however after a sufficient time period, anoles exposed to ALAN increased their metabolic rates during the evening, but not during the day! During this experiment, they also found that ALAN anoles were far hungrier and ate more often than lizards that weren’t exposed to light at night. The term ‘midnight snack’ definitely comes to mind here! Michelle suggests that much like when humans get exposed to changes in sleeping patterns, anoles undergo some energetic changes, causing them to eat more and having to burn more energy. Maybe next time think twice about keeping that porch light on during the waning hours of the evening- give the wildlife some much needed rest.

SICB 2020: Variation in Anole Sperm and Testis Morphology

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On January 8, 2020

In All Posts, New Research

Another star undergrad alert! If you’ve ever followed the work that comes out of Dr. Michele Johnson’s lab at Trinity University, you’ll know that she produces some incredible science and some even-more incredible undergraduate researchers. Isabela Carson is no exception!

Isabela’s poster was focused on studying intraspecific variation in lizard sperm and testis morphology- she described differences in the size and shape of different testis and sperm features for 6 different species of anole. A lot of this work was founded on Dr. Ariel Kahrl’s dissertation work on describing sperm evolution in anole lizards, and her collaborations with Dr. Johnson’s lab and students always produce some awesome talks and posters wherever they are presented. Isabela wanted to know if longer sperm are produced from lizard species that have larger seminiferous tubules- the part of the testis where sperm are produced, matured, and transported. She found an inconsistent pattern across anole lizards where larger tubules don’t always produce longer sperm.

In talking with Isabela, she noted that there are some big inconsistencies between the external morphology of testes and the sperm they produce, and that there might be some larger ecological or evolutionary patterns at work that go into describing how sperm evolve in different species. I would bet that one day we are going to have data on testis shape and size and sperm length for all anolis species, and there are going to be some awesome patterns and studies that come out of that work. And we definitely have to give heaps of credit to the awesome biologists who are working towards it!

SICB 2020: Artificial Light Doesn’t Influence Immune Responses in Green Anoles

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On January 8, 2020

In All Posts, New Research

The Howey lab showed up to work at SICB 2020! In keeping with the theme of how urbanization and artificial light at night (ALAN) impacts wildlife populations, Elizabeth Kenny, an undergraduate researcher at the University of Scranton performed a study to describe the influence of artificial light on the immune response in green anoles (Anolis carolinensis).

The researchers used a test for immune response called a phytohemagglutinin test (PHA-L), where they injected the hindlimbs of green anoles with PHA-L and measured how much the foot swelled after both a 24 and a 48h hour period. But rest assured! PHA-L tests are temporary, only induce localized swelling, and have no larger impacts on the health of the organism; it’s sort of like if you’ve ever had a tuberculosis test done at your local physician. Interestingly, Elizabeth found no difference in swelling between green anoles exposed to ALAN and to green anoles that had not been exposed to ALAN. However, Elizabeth suggested that green anoles could respond sufficiently to ALAN by changing how they use the energy within their bodies and where they allocated those limited energetic stores, which provides a lot of support for the work of Michelle D’Allesandro and Meg McGrath. Altogether, the three undergraduate researchers of the Howey lab created a convincing and interesting story about how urban environments influence the energetics and physiology of city-dwelling lizards. Great stuff!

SICB 2020: City Anoles Have Bigger Toes!

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On January 8, 2020

In All Posts, New Research

Urbanization was a big theme at SICB 2020 this year, and studies of how city life influences wildlife populations are really important to help us understand the effects of human activity on natural environments and animals. One of the most rapid ways in that city-dwelling animals can adapt to these new environments is by changing the shape and size of various morphological traits.

Anoles in their natural habitat do tend to be tree-dwelling, or arboreal lizards, and they spend a lot of time climbing to find food resources, regulate their body temperature, and do other ecological activities. A lizard that relies so much on climbing performance frequently uses its claws and toe pads in its climbing ventures, so one of the first changes that city anoles might exhibit is changes in toe pad or claw shape to better climb on slick city surfaces (say that 3 times fast!). To get at this question, Bailey Howell from the Mississippi University for Women, along with her co-authors Travis Hagey and Kristin Winchell, compared urban crested anoles (Anolis cristatellus) to forested crested anoles and found that toe pads in urban anoles are longer and wider than toe pads from lizards in natural environments.

Bailey goes on to discuss that these toe pads that have an increased area might be better for urban anoles to climb on slicker and smoother substrates found in city environments. Bailey is going to continue adding to her dataset by incorporating more anoles and testing additional hypotheses such as measuring performance differences between urban and forested anoles. Stay tuned for more urban anole work!

SICB 2020: Gene Expression Can Lead to Size Dimorphism in Anole Lizards

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On January 8, 2020

In All Posts, New Research

The Panamanian slender anole (Anolis apletophallus).

In keeping with the previous year, Albert Chung (now a Ph.D. student at UCLA with Shane Campbell-Staton), presented in the prestigious Division of Ecology and Evolution Raymond B. Huey best student paper session of SICB2020. Albert’s work encompasses a very old, enduring, and important question in biology: how males and females of the same species exhibit differences in so many traits, despite the fact that males and females share a common genome.

A male brown anole from the island of Great Exuma, in The Bahamas.

This dynamic is called sexual conflict: when what is best for one sex might not be the best for the other sex, and has challenged biologists for decades to study a multitude of incredible organisms to answer this question, including anoles! Albert and his collaborators addressed this question by studying two species of anole, the brown anole (Anolis sagrei) and the Panamanian slender anole (Anolis apletophallus). Brown anoles are one species where males are super large compared to females, whereas in the slender anole, males and females are relatively the same size.

Albert et al. described differences in the genes expressed in both males and females to understand what factors promote the development of male-biased size dimorphism. They found that differences in gene expression between males and females was highest in gonad tissue compared to liver and brain tissue, and that when female lizards are supplemented with additional testosterone (traditionally viewed as a hormone more highly concentrated in males of a given species), their gene expression profiles look like those of male lizards. They also found that liver tissue exhibits the greatest differences in sex-biased gene expression, because the liver is one organ responsible for supplying the body with the energy and molecules needed for growth. They suggest that differences in gene expression between males and females might be one factor promoting the evolution of size differences between the sexes, and that physiological controls on these genes could play prominent roles in having males and females exhibit huge differences in traits despite sharing a similar genetic makeup.

 

SICB 2020: Brown and Green Anoles Have Similar Activity Levels Across Temperatures

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On January 7, 2020

In New Research

Brown anoles (Anolis sagrei) are found in many urban habitats.

Invasive species are a common ecological issue worldwide. In certain situations, they can prey on, outcompete, or otherwise disrupt the ecology of native species, potentially leading to population declines or extirpation.

The brown anole (Anolis sagrei) is native to Cuba and surrounding Caribbean islands, but has been repeatedly introduced to mainland North America via Florida over the past ≈100 years. Brown anoles have continued to spread and now occupy most of Florida, along with areas of the Gulf Coast. These anoles are particularly adept at exploiting urban habitats, such as Houston and New Orleans, where they may attain higher body size and compete with the native green anole (Anolis carolinensis). Brown anoles can outcompete green anoles in habitats such as the ground or lower levels of vegetation, where they can use their larger, more muscular bodies to chase off the native anoles or even prey on young green anoles. While green anole populations are likely not extirpated by brown anoles, they shift their locations higher into vegetation, to avoid competition with brown anoles.

The ability of these species to maximize their activity at different temperatures may play a role in determining the outcomes of interactions between brown and green anoles. While green anoles are present throughout the southeastern US and can tolerate colder temperatures, brown anoles may be ancestrally adapted to higher, more tropical temperatures. Lucy Ryan, a masters student in the Gunderson Lab at Tulane University decided to investigate this possibility by monitoring the activity levels of each species at a variety of different temperatures. The research team hypothesized that, based on their thermal preferences, brown anoles would have higher activity levels than green anoles at both higher temperatures and over a wider range of temperatures. Lucy conducted focal observations of anoles to quantify activities such as feeding, displaying, and moving. They measured the temperature of each anole’s microhabitat with a copper model containing a thermocouple.

Over an 18° C range of temperatures, Ryan found that there was no difference in the activity levels of the two species. These results, while surprising, suggest that effects of temperature on activity are not driving the competitive advantage of brown anoles over green anoles. In fact, since both species’ activity rates peak at similar intermediate temperatures, this situation may increase competition between brown and green anoles. Ryan plans to continue this work through the winter and spring to determine whether there are any species differences over an entire year of activity which may impact this system. Stay tuned and follow them on Twitter!

Green anole activity rate, including dewlap displaying, shows a peak at intermediate temperatures.

SICB 2020: Invasive and Native Anoles Have Different Dietary Niches

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On January 6, 2020

In All Posts

Chelsea Connor presenting her research at SICB 2020

Invasive species can often compete for resources with native species, which can have a negative impact on the community. This is an especially common occurrence when it comes to the diet of these competing species. It is important to investigate the diet of both the invader and the native species in order to determine whether this competition is present and if it will cause negative effects in the future.

Chelsea Connor grew up on the island of Dominica. She is currently an undergraduate student at Midwestern State University in Wichita Falls, Texas in the lab of Dr. Charles M. Watson. Her research addresses the dietary niche overlap of native and invasive species on her home island of Dominica. For this research, Chelsea and another undergraduate student, Destiny Zinn captured and collected feces from Anolis oculatus (a native species) and Anolis cristatellus (an invasive species) on Dominica. They successfully extracted and amplified a region of the cytochrome oxidase I gene from 44 samples. Then they ligated the PCR products and transformed them into E. coli to grow on a plate. After this, they sequenced the resulting clones and placed them into Molecular Taxonomic Operational Units, which were matched using the databases BOLD and GenBank with the help of Daniella Biffi and Dr. Dean Williams at Texas Christian University. They calculated the similarity of diets using the Sørenson coefficient.

Chelsea and her collaborators found a shockingly low degree of dietary overlap, discovering that these two species of anoles on Dominica consume different arthropod prey. They identified 40 prey species in this experiment, and only 4 species were contained in the diet of both the native and invasive anoles. Chelsea emphasizes that there may be dietary niche partitioning, which could explain how the two species are able to coexist across the island and avoid competition.

SICB 2020: Green Anoles Have Higher Heat Hardening Capacity Than Brown Anoles

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On January 6, 2020

In New Research

Ectotherms rely on interactions with surrounding thermal environments to regulate their body temperature. If their body temperatures get too low or too high, ectotherms may be unable to move effectively or escape dangerous temperatures, potentially leading to death. One plastic physiological response which may help ectotherms avoid the effects of dangerously high body temperatures is heat hardening. Heat hardening is a type of physiological flexibility that entails an organism increasing its heat tolerance after a previous exposure to high temperatures. In areas with high temperatures, differences between ectotherms in their abilities to effectively conduct heat hardening could affect competition between them.

A green anole (Anolis carolinensis) basks at an elevated perch.

Sean Deery, a masters student in the Gunderson lab at Tulane University, chose to investigate heat hardening capacity in two species of anoles, the native green anole (Anolis carolinensis) and the invasive brown anole (Anolis sagrei), both of which are present in New Orleans. As brown anoles have expanded throughout the area, they have displaced green anoles, forcing them higher into vegetation, a pattern repeated in other areas of the southeastern U.S. 

Brown anoles are particularly adept at exploiting urban habitats, where temperatures may be considerably higher than surrounding natural areas due to the urban heat island effect. Sean wondered whether the competitive advantage of brown anoles over green anoles might be based in part on a superior heat hardening capacity, which could support their dominance in urban areas.

(a) A male green anole and (b) and a displaying male brown anole in Florida.

To quantify heat hardening in this system, Sean captured green and brown anoles and first measured their upper critical thermal maximum (CTMax) by steadily ramping up their body temperatures until the lizards lost coordination. CTMax represents a temperature that could prove lethal to a lizard as it would be unable to escape these hot conditions. After allowing lizards to recover, Sean measured their CTMax again after periods of 2, 4, and 24 hours. Heat hardening was calculated as the difference between the initial CTMax and the subsequent measurement after exposure to those initial high temperatures. 

Sean’s results were surprising: He found that brown anoles showed no evidence of heat hardening at any time after an initial measurement of CTMax. In fact, brown anoles showed a reduction in CTMax, suggesting that the initial testing may have stressed them and reduced their ability to cope physiologically with higher temperatures. Green anoles on the other hand showed a moderate heat hardening response, with significant increases in CTMax just 2 hours after exposure to high temperatures. Sean’s results also suggest that individual lizards with lower initial CTMax values showed greater heat hardening. 

For now, it appears that heat hardening is not a factor driving invasions of brown anoles in the southeastern U.S., but the differences between these two species are intriguing. Sean hopes to expand on this work by investigating molecular mechanisms that may support or inhibit heat hardening, such as expression of heat shock proteins.

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