Kudos to Anat Belasen, U-M EEB graduate student, on winning the department’s 2019 Outstanding Paper Award for her Frontiers in Ecology and Evolution paper. The award was announced last week at the annual EEB spring picnic by Professor and Chair Diarmaid Ó Foighil.
Belasen is first author of "Long-Term Habitat Fragmentation Is Associated with Reduced MHC IIB Diversity and Increased Infections in Amphibian Hosts," published Jan. 10, 2019. Coauthors are her advisor U-M EEB Professor Timothy James and colleagues from the University of Massachusetts and State University of Campinas, Brazil.
“Anthropogenic (human-caused) habitat fragmentation and disease are two major stressors that have contributed to global amphibian declines,” explained Belasen. “We know a decent amount about the effects of each of these stressors but little about how they interact. This is an issue because in many (maybe even most) cases, both stressors impact wild populations simultaneously. I hypothesize that the genetic impacts of habitat fragmentation (e.g., increased inbreeding) have contributed to the rise in disease we've seen in amphibians in the last few decades. However, because it takes many generations for inbreeding to erode genetic diversity, it can be difficult to detect genetic impacts of anthropogenic fragmentation that occurred in the last few hundred years. Fortunately, model systems exist that were naturally fragmented thousands of years ago that we can use to gain insight to the future impacts of contemporary fragmentation.
“In this study, which serves as the first chapter of my Ph.D., I test the hypothesis that fragmentation affects genetic diversity and leads to increased infections in amphibians. I used a model system to look at the long-term effects of fragmentation: a set of land-bridge islands that were connected to the mainland approximately 20,000 years ago but were separated through rising sea levels due to glacial melting at the end of the Last Glacial Maximum. I sampled island frog populations that have been isolated since island formation as well as mainland frog populations to provide baseline information. I found that island frogs had lost genetic diversity on the population level not just across the genome but specifically at a gene associated with immune function – this was surprising because these immune genes often show high diversity even in highly inbred populations. I also found that individual-level genetic diversity at this immune gene was predictive of how many potentially parasitic microbes were found on the frogs' skin. Inbred island frogs also hosted a relatively higher diversity of potential parasites than mainland frogs. In all, this study shows that fragmentation can disrupt the maintenance of genetic diversity at important immune genes and that this increases infections.
The committee that reviewed the papers in competition included EEB postdocs Timothy Cline, Haoxuan Liu and Laura Lopez. They wrote that the paper starts with an interesting question, followed by well thought out and cleverly designed approaches. The results are informative and clearly presented. Furthermore, the paper is well-written and will have a significant impact in its field.
Compiled by Gail Kuhnlein