Environment-driven shifts in ant communities over six decades

In the paper “Temperature-driven homogenization of an ant community over 60 years in a montane ecosystem“, Anna Paraskevopoulos and colleagues have used ants as a model to quantify community-level changes in species composition over a 60-year period, by comparing historical and current data of species composition in a relatively undisturbed area in Colorado. The authors have shown increased ant species richness, reduced diversity across sampled sites, and increased species richness and abundance in subset of sites in ant communities sampled in 2021 versus historical communities from 60 years ago. Furthermore, when comparing at the microsite level, authors observed an increase in occurrence of species that can forage across wider temperatures. While these results are not in line with the global decline in species richness and diversity due to climate change, they do provide a definite support for landscape-specific critical shifts in communities due to environmental changes.

We sat down with the first author, Anna Paraskevopoulos, to discuss the key findings and implications of their research that was published in the journal Ecology earlier this year.

An Interview compiled by Salvatore Brunetti and Rohini Singh

MNB: Could you tell us a bit about yourself?

AP: I am a 4th year PhD student in the Resasco Lab at the University of Colorado, Boulder in the Department of Ecology and Evolutionary Biology.

MNB: Could you briefly outline your research on “Temperature-driven homogenization of an ant community over 60 years in a montane ecosystem” published in ECOLOGY in layman’s terms?

AP: In the late 1950s, entomologist Robert Gregg and his student John Browne surveyed the ant populations at 33 sites in Gregory Canyon near Boulder, Colorado, USA. This study examined changes in ant communities over a 60-year period by comparing contemporary community composition and species occurrence data to the survey conducted by Browne and Gregg (1969). The location of the study is maintained currently by the City of Boulder and has remained largely unchanged over the past century. We found that the contemporary ant communities were more similar in terms of composition than the historical communities. In the last 60 years, over ten ant species have moved into Gregory Canyon that were previously undetected. However, there were also 12 species that were recorded in the historical study that we were unable to detect in the contemporary community. Lastly, ants that foraged at a broader range of temperatures exhibited increased occurrence throughout across sites compared to the historical study.

MNB: What is the take-home message of your work?

AP: Our work highlights that large community changes can still occur in undisturbed areas where habitat degradation has been minimal. We also show the importance of pairing historical and contemporary data. Ants are the movers and shakers in an ecosystem. They perform important ecosystem functions, so it’s really important to understand how they’re changing in the face of climate change.

MNB: What was your motivation for this study?

AP: I am very interested in how ant communities are impacted by climate change. My advisor, Dr. Julian Resasco, and one of my committee members (the other co-author on the paper), Dr. Nate Sanders, recommended I read Browne and Gregg’s 1969 paper so the inspiration for the resampling came from them!

MNB: What was the biggest obstacle you had to overcome in this project?

AP: The biggest obstacle was georeferencing the maps that were included in Browne and Gregg (1969) to ensure that we had the same sampling sites and ant species collection locations as Browne and Gregg had.

MNB: What do you think is the future for this particular field of ant research?

AP: Being able to resample historical studies, can give us a glimpse into how insect biodiversity may be changing over time. Unfortunately, we don’t have a lot of monitoring data for insects which makes this particular field a bit challenging.