Colin Donihue

Exciting news: Our next paper on the effects of hurricanes on Anoles has just been published in PNAS! Here’s a link to the paper.

This study has been on my mind since our first paper about the lizards on Turks and Caicos before and after Hurricane Irma back in 2017. You can see some terrific video about that research here:

The initial paper was evidence for natural selection due to hurricanes – the hurricane survivors had larger toepads. It left me with two questions though: the first was what does this short-term selection mean for the next generation of lizards? The second question was is this a special case, unique to the Turks and Caicos anole, or is this a more wide-spread phenomenon?

To answer this question, we returned to Turks and Caicos and measured the offspring of the hurricane survivors. What we found was that their toepads were still significantly larger than the population average from before the hurricane, and about the same size as those of their parents. In other words, those large-toepad lizards that survived the storm seemed to have passed along that trait to the next generation. Here’s figure 1 from the paper illustrating that trend:

What about Turks and Caicos being a special case? Well, we don’t have great before/after data on other anoles like we just happened to have for the population on Turks and Caicos, so I had to get a little creative. Essentially, instead of looking at patterns in toepad areas after hurricanes, I decided to compare populations that had been hit relatively more or less frequently by the storms. The prediction being that those populations that had been hit more often would tend to have larger toepads.

In order to do so, I reached out to Alex Kowaleski, a post-doc at Penn State who’s research specialty is hurricanes. He was able to use a dataset from NOAA to interpolate the location and windspeed of every hurricane in the Atlantic basin over the last 70 years.

Armed with the hurricane data, I next investigated toepads at two geographical scales: the first across 12 populations of the widespread Anolis sagrei. What we found was that those sagrei populations that had experienced more hurricanes, tended to have larger toepads. You can see that here:One of the best things about studying anoles is their incredible diversity. They range from the US to Brazil and there are hundreds of species throughout. With the help of collaborators, I got pictures of the toepads of 188 different species of anoles across this range. We found the same pattern: species that had experienced more hurricanes in the last 70 years also had larger toepads, on average.

 This suggests that hurricanes are having an important, and durable effect on the evolution of these lizards at multiple different geographical scales – the local, the regional, and the continental. Climatologists and meteorologists predict that severe hurricanes are going to become more frequent due to climate change. This study suggests that those severe hurricanes may have important effects on the evolution of the populations and species in the path of those hurricanes. My hope is for researchers to investigate this pattern in other systems – plants, insects, snails, corals – to see if there are indications in other taxa that hurricanes are driving patterns of trait diversity in the Neotropics.