Why are some populations and species more susceptible to novel stressors than others?
Research in the Belasen lab is driven by an interest in the conservation of biodiversity, and in particular the vulnerable herpetofauna (amphibians and reptiles), fondly referred to as "herps." Other than being fascinating organisms to study, herps play critical roles in ecosystem function and are particularly vulnerable to global change. The stressors we focus on include emerging infectious disease, habitat fragmentation, and climate change.
Physalaemus signifer, a tiny leaf litter frog found only in Brazil's Atlantic Forest. This species is especially sensitive to habitat fragmentation.
Emerging infectious wildlife disease contributes to biodiversity loss.
Our ongoing research focuses on the genetic mechanisms driving susceptibility vs. resistance/tolerance to amphibian chytridiomycosis, one of the most destructive contemporary wildlife diseases.
Our ongoing research focuses on the genetic mechanisms driving susceptibility vs. resistance/tolerance to amphibian chytridiomycosis, one of the most destructive contemporary wildlife diseases.
Researching the drivers of susceptibility vs. resistance to protect frogs from a deadly fungus
Dr. Belasen's first encounter with foothill yellow-legged frogs (Rana boylii)! Visiting field sites (California's Central Coast,
March 2020)
Two decades of scientific research on the amphibian-killing fungus Batrachochytrium dendrobatidis (Bd) have shed light on Bd’s distribution, biology, and how it causes the disease amphibian chytridiomycosis. However, we still don’t have a complete understanding of what makes some amphibians so susceptible to Bd (they get really sick and die) while other amphibians seem to be resistant or tolerant (they don’t get as sick and they survive).
Together with some truly wonderful collaborators, we are assessing the mechanisms driving intraspecific variation in Bd susceptibility using a combination of approaches, including synthetic and collaborative spatiotemporal analyses of Bd incidence in Rana boylii, and museomics in Rana yavapaiensis. Both of these species occur in western have experienced declines over the past several decades, and show variation in their susceptibility or response to Bd across populations. Check out our first paper exploring variation in Bd responses through space and time in R. boylii here. Stay tuned for updates on our museomics study on R. yavapaiensis!
Together with some truly wonderful collaborators, we are assessing the mechanisms driving intraspecific variation in Bd susceptibility using a combination of approaches, including synthetic and collaborative spatiotemporal analyses of Bd incidence in Rana boylii, and museomics in Rana yavapaiensis. Both of these species occur in western have experienced declines over the past several decades, and show variation in their susceptibility or response to Bd across populations. Check out our first paper exploring variation in Bd responses through space and time in R. boylii here. Stay tuned for updates on our museomics study on R. yavapaiensis!
Habitat fragmentation, the division and reduction of once-contiguous habitats,
is likely to drive increased wildlife susceptibility to other stressors.
We have explored this hypothesis in two systems, described below.
is likely to drive increased wildlife susceptibility to other stressors.
We have explored this hypothesis in two systems, described below.
Habitat fragmentation increases disease susceptibility in tropical amphibians
Dr. Felipe Toledo, one of our main collaborators from Brazil. Here Felipe is accompanying my advisor Tim and me on a trip to a little explored land-bridge island off the coast of São Paulo state.
One likely explanation for variation in disease susceptibility within host species is variation in genetic diversity. Genotype could determine resistance to emerging infectious disease, especially at immunogenetic loci, genetic regions involved in the immune response. Genetic differences and/or population fragmentation (via reductions in dispersal) could also contribute to variation in the host-associated microbiome, the host's resident community of microscopic organisms (including bacteria, fungi, and other tiny eukaryotic beasties).
To examine these potential mechanisms of variation in disease susceptibility, we worked with Brazilian biologists to sample frogs in the Atlantic Forest of Brazil in three areas that exemplify different challenges to amphibian genetic diversity and dispersal. In these systems, we evaluated whether fragmented frog populations exhibit effects on pathogen infection rates, genetics and immunogenetics, and microbiome diversity relative to continuous baseline host populations.
Check out our papers from this work in Frontiers in Ecology and Evolution, Ecology and Evolution, and Immunogenetics. Please don't hesitate to reach out for pdfs of these publications.
To examine these potential mechanisms of variation in disease susceptibility, we worked with Brazilian biologists to sample frogs in the Atlantic Forest of Brazil in three areas that exemplify different challenges to amphibian genetic diversity and dispersal. In these systems, we evaluated whether fragmented frog populations exhibit effects on pathogen infection rates, genetics and immunogenetics, and microbiome diversity relative to continuous baseline host populations.
Check out our papers from this work in Frontiers in Ecology and Evolution, Ecology and Evolution, and Immunogenetics. Please don't hesitate to reach out for pdfs of these publications.
Local adaptation drives thermal ecology in Mediterranean lizards
Dr. Belasen conducting vegetation quadrats on Naxos, the largest island in the Cyclades. Photo by Binbin Li (2011)
The Mediterranean is a global hotspot of lizard diversity, but also stands to become significantly hotter and drier with progressed climate change. We worked with Greek collaborators to evaluate the sensitivity of Greek land-bridge island lizards to future climate change.
Contrary to our expectations, smaller, genetically impoverished populations did not exhibit reduced variability in thermal ecology phenotypes. However, water loss rates appeared to vary by population, with lizards coming from hotter, drier sites able to maintain lower rates of water loss than those from cooler, wetter sites. And these differences seem to be heritable! Taken together, these findings suggest that local adaptation could make some populations (particularly those adapted to cool, wet habitats) more sensitive to warming and drying conditions.
Read more in our paper published in Oikos!
Contrary to our expectations, smaller, genetically impoverished populations did not exhibit reduced variability in thermal ecology phenotypes. However, water loss rates appeared to vary by population, with lizards coming from hotter, drier sites able to maintain lower rates of water loss than those from cooler, wetter sites. And these differences seem to be heritable! Taken together, these findings suggest that local adaptation could make some populations (particularly those adapted to cool, wet habitats) more sensitive to warming and drying conditions.
Read more in our paper published in Oikos!