Dr. Carlos Garcia-Robledo, Assistant Professor in the Department of Ecology and Evolutionary Biology at the University of Connecticut, discusses with us his recently accepted paper, “Evolutionary history, not ecogeographic rules, explains size variation of tropical insects along elevational gradients.”

What’s your paper about?

Temperature is known to affect organismal body size. For example, individuals from different populations, or species from the same genus living at higher elevations or latitudes, are expected to display larger body size than organisms inhabiting warmer environments. This observation inspired various “ecogeographic” rules (e.g., Bergmann’s rule, the temperature-size rule and James’ rule). However, exceptions are commonplace, showing that ecogeographic rules are more general tendencies rather than absolute natural laws. An alternative explanation tested in our study is that patterns in body size along elevational gradients are the product of evolutionary history.

Rolled-leaf beetles (Cephaloleia: Chrysomelidae) are insect herbivores of the “banana-like plants” (order Zingiberales). This is one of the oldest known plant-insect interactions (between 40-60 MY old). Rolled-leaf beetles are an emerging model system, used in my laboratory to understand the effects of global warming on tropical biotic interactions.

We tested the effects of temperature on body size at both population and community levels for over two thousand individuals from 64 populations and 40 species distributed along two tropical mountains in Costa Rica. Our main conclusion is that evolutionary history, not ecogeographic rules, explains size variation of rolled-leaf beetles along tropical elevational gradients.

What is the background behind your paper?

I am an Assistant Professor at the University of Connecticut – Department of Ecology and Evolutionary Biology. I started working on the ecology and evolution of rolled-leaf beetles when I was a PhD student at the University of Miami. I continued my research in this system as a Postdoctoral Fellow at the National Museum of Natural History – Smithsonian Institution. In a previous study (García-Robledo et al. 2016. PNAS 113.3: 680-685), we discovered that high-elevation beetle species have lower thermal tolerances than rolled-leaf beetle species in the lowlands.

Together with Vikas Sarathy and Kes Lippert, two talented undergraduate students at the University of Connecticut, we wondered if such differences in thermal tolerance were associated with changes in body size. If warmer temperatures are associated with a reduction in body size, we thought that one possibility is that tropical insects will become smaller under projected global warming. Kes and Vikas spent long hours measuring thousands of specimens from our laboratory collection. Christina Baer, postdoctoral researcher in my laboratory, joined the team to explore the effects of evolutionary history on body size patterns.

What are the key messages of your article? Two quotes:

“At the interspecific level, body size is predicted by evolutionary history, not ecogeographic rules”

“We should not assume that global warming will inevitably lead to body size decreases for ectotherms”

About the Author

How did you get involved in ecology?

I did my undergraduate studies in the Department of Biology, Universidad de Los Andes in Bogota, Colombia. In my first year, I was not sure if I wanted to continue in the Biology program. My Ecology professor suggested that I take a “research semester” in a field station that he started in the Colombian Amazon. After flying over the Amazon in a World-War II era DC3 plane, and a two-day boat ride through the jungle, I arrived to Sierra de La Macarena, a Precambrian rock that connects the biotas of the Andes, the Amazon, the Orinoco and the Guiana shield. A couple of months after my arrival, my undergraduate advisor visited the field station and asked me if I still wanted to change programs. It was an easy sell. Of course, I wanted to be an ecologist. I was hooked for life after experiencing the most biodiverse spot on earth!

Read the paper in full here.