Author: Chris Robinson

Rachana applying fluorescent powder to a wild brown anole

If you’ve ever tried to note how often lizards mate, you’ve likely found yourself staring at an individual for hours at a time, sometimes with little to no movement at all, let alone observing copulations! Further, if you’re unable to catch the animal after your behavioral observations, you may not be able to draw any conclusions about traits that influence how successful an individual is at mating with another.

Rachana Bhave, a fourth year PhD candidate in Bob Cox’s lab at University of Virginia, studies pre- and post-copulatory sexual selection in brown anoles (Anolis sagrei). One of her interests includes estimating mating rates in the wild and, in particular, testing if traits such as body size directly influence these rates. Given the power required to detect selection statistically, using simple behavioral observations can be inefficient. Further, because selection is a measure of covariance between phenotype and fitness, one needs phenotypic values for each individual within her analyses. Thankfully, Rachana was able to come up with a robust technique to estimate mating rates using an island population of brown anoles in Florida: fluorescent powders!

To understand how size affects mating rate in the brown anole, Rachana and colleagues caught 153 adult male lizards in May and 128 adult male lizards in July, weighed them, and then assigned them to one of four fluorescent powder treatments. Each mass quartile was painted with a unique color of fluorescent powder on their cloaca and released to their initial capture location. After two days, all females on the island were captured and their cloaca were examined under UV light to look for the presence and color of fluorescent powder, which would suggest that she mated with a painted male. Using this technique, Rachana found that within two days, 24% of the captured females had mated in May and 48% had mated in July. These rates were shockingly high for such a short time frame!

A) Powdering an adult male brown anole; B) copulating brown anoles; C) powder visible on the cloaca of a female brown anole, evidence of copulation
Images from Rachana’s poster

Further, she found that both larger males and larger females mated significantly more than smaller males and females across the two sampling periods. Interestingly, 2% of females had multiple colors on their cloacas, which suggests they mated multiple times with males from different size classes in the two-day span. Because multiple matings within the same size class would be undetectable, this is likely an underestimation of multiple matings in the wild.

Next, Rachana plans to quantify male reproductive success using genetic parentage analysis to begin to tease apart how pre- and post-copulatory selection influences selection. We are all looking forward to her results next year! Meanwhile, you can take a look at her poster to find out more on her website.

Emily Watts with her poster in NOLA at SICB 2017.

Great new aggression work from the McGlothlin lab! Emily Watts, an undergraduate student, presented a poster on Saturday about differences in aggression between island populations of A. sagrei.

Previously, the McGlothlin lab quantified aggression of brown anoles from Eleuthera, Exuma, North Andros, and San Salvador in the Bahamas. They found that individuals from Exuma and North Andros were more aggressive than from Eleuthra and San Salvador. Emily wanted to know if these population-level differences were a result of genetics or of the environment.

To test this, she bred lizards from Eleuthra and Exuma in the lab using a full cross design and raised the offspring in a common garden environment. When the males were one year old, Emily used enclosure trials to quantify aggression for each individual. The results were not what she expected. She found that aggression was independent from where a lizard’s parent came from, but was instead influenced by the environment.

Next, Emily will be testing offspring from the North Andros – San Salvador crosses they also performed. Additionally, because aggression was not repeatable for individuals, Emily will be testing each male again against a mirror to quantify individual aggression independent of partner aggression.

Thanks for sharing, Emily! We look forward to next year’s presentation.

Maria Jaramillo with her poster, doing her best anole impersonation.

Behavior can be extremely variable, even within a species. To control for this inherent variability while assessing individual responses to a visual stimulus, some researchers have begun using videos in their experiments. Maria Jaramillo, an undergraduate student in Michele Johnson’s lab, is curious about how anoles process visual information and if videos and live encounters are processed similarly in the brain. On Saturday, Maria provided us with an update of her work.

For this experiment, Maria used 40 adult male A. carolinensis which were exposed to one of four treatments for 15 minutes: 1) another live anole, free to display; 2) a looped video of an anole, which displayed for about 30 seconds, waited 15 seconds, then displayed again; 3) a scrambled version of the previous video; 4) or a control video of a lizard perch. She recorded the behavior of these lizards, then sacrificed them in order to collect their brains.

Maria found that the lizards paid close attention to the live anole, the video of the anole, and the scrambled anole video, but significantly less attention to the control video. Interestingly, though, males displayed significantly less to the scrambled and control videos than to the live anole and the normal video.

Next, Maria will use immunocytochemistry to quantify c-fos+ neurons in five brain regions associated with visual processing and the social behavior network. c-fos is an immediate early gene that is transcribed when neurons are activated, and c-fos+ neurons were likely stimulated in response to the visual stimuli Maria presented. She will then use the ratio of ­c-fos+ neurons to total number of neurons in that brain region to quantify neural activity in the five brain regions and see how these differ between stimulus treatments.

This is really exciting work and we can’t wait to see the end result!

Hello from unexpectedly cold New Orleans! Our coverage of SICB 2017 continues and we hope you will enjoy the increased posting over the next few days.

On Friday, David Delaney presented more data from his Master’s thesis from Dan Warner’s lab further exploring how adult and juvenile A. sagrei interact. Previously David showed that the presence of adults did not affect microhabitat use, but that high densities of adult males decreased survival in juveniles, especially in smaller lizards.

This year David presented intriguing data suggesting that the presence of adult males influenced how juveniles sat on their perches. He found that the presence of adult males alter both horizontal and vertical orientation of juveniles. When one male is present, juveniles increase horizontal orientation over time, but if three males are present, juveniles face upwards more than when no or only one male is present. Additionally, they also face the trunk of the tree more than away from the tree when they are horizontal and adults are present. Because of the chance of juvenile saurophagy, David suggests this helps juveniles to monitor where the adult males are to prevent being eaten.

Check back often to read about more great research being presented at SICB 2017!