Overview Research in our lab is focused on contemporary evolutionary responses to environmental change, particularly in the context of roads and runoff contaminants. We use field, lab, and computational techniques to address diverse questions about local (mal)adaptation and conservation. Our interests lie at the intersection of ecology and evolutionary biology. While these two disciplines have been viewed traditionally as distinct approaches to explaining the natural world, biological organisms know no such divide. To advance our knowledge beyond this constructed dichotomy, we incorporate theoretical and applied insights and approaches from both of these disciplines to answer questions about the responses of organisms to our ever-changing environment. In particular, I study the consequences of roads and runoff on wetland dwelling amphibians. For example, wood frog and spotted salamander eggs laid into these environments typically have 20 and 35% lower hatching success than those laid into wetlands located several hundred feet away from the road. In spite of this profound consequence, I have found that roadside populations of the spotted salamander are locally adapted to these conditions. This evidence suggests that these populations are evolving in tempo with severe environmental change.
Taking water quality measurements in a roadside pool at the outset of breeding season.
One of the lead actors in this eco-evolutionary play -- the wood frog.
Road effects Roads impose a diverse suite of negative effects on wild populations. Pollution, road-kill, and habitat fragmentation are just a few of the common stressors found across modern landscapes traversed by roads. Owing to the pervasiveness of the global road network, these impacts are widespread, and extend well beyond the footprint of the road surface itself. For instance, an estimated 20% of the landscape in the U.S. is ecologically affected by roads. While these ecological consequences of roads are well described, evolutionary consequences remain poorly understood. Yet owing to intraspecific variation, road effects are not universally detrimental to all individuals in a population, and indeed can act as agents of natural selection. The nature of this selection and the response to it will ultimately influence the long-term persistence of populations exposed to road effects. Thus, developing evolutionary-based insights will be crucial to understanding the full impact of roads on natural populations.
For amphibians, roadside habitats can be extremely harsh places to make a living. In the northeastern US, these wetlands can accumulate enough salt from winter deicing to classified as brackish water. This is not something most amphibians are accustomed to, and it is not without consequence. Our previous work has shown that evolutionary responses to roads and runoff pollution differ among species, even among co-habiting, related species breeding and dwelling in the same wetlands. For instance, roadside populations of a salamander are locally adapted to roads and road salt pollution. These populations achieve higher fitness in roadside wetlands compared to populations experimentally transplanted there from unpolluted wetlands away from roads. Similar manipulations with a species of frog reveal the exact opposite effect: roadside frog populations achieve lower fitness in their home wetlands compared to frogs transplanted there from unpolluted sites. This pattern of ‘local maladaptation’ is surprising given that adaptive variation is present in nearby populations located away from roads. Several processes can contribute to this maladaptive outcome, including contaminant transfer from parent to offspring, maladaptive evolution, DNA damage, and biased gene flow patterns.
Motivated by these divergent outcomes among species, our work is aimed at understanding the full nature of environmental change in habitats affected by roads. We are guided by the overarching goal of developing predictive understanding of population level responses to roads and runoff pollution. Toward that goal, we work across biological scales (from molecular to community level) to identify differential fitness patterns across populations and investigate potential mechanisms (e.g. genetic, epigenetic, physiological, demographic) underlying such differences. In complement, we are interested in characterizing the suite of contaminants found in roadside wetlands (e.g. road salts, heavy metals, PAHs). We are particularly interested in describing spatio-temporal variation of these contaminants across landscapes and assessing the accumulation and transgenerational movement of contaminants in amphibians relying on roadside wetlands. In the future, we plan to investigate additional stressors related to climate change and disease dynamics to more fully understand the impacts of environmental change on roadside habitats.
Epigenomics We are investigating genome-wide methylation patterns in wood frog populations originating from roadside and woodland populations. We are interested in understanding whether roadside habitats induce different methylation patterns and whether methylation differs among different organs (e.g. skin, liver, gills). Ultimately, we aim to relate epigenomic variation to differential fitness and patterns of maladaptation in roadside versus woodland populations.
Understanding maladaptation For most of the history of the field of evolutionary biology, scientists have marveled at the process of natural selection and the adaptations that result. By contrast, the failings of evolution have been given considerably less attention. In turn, our understanding of the dynamics and distribution of maladaptation are severely limited. We are developing a cohesive framework for studying maladaptation. Stay tuned for two special issues coming out on the topic in 2019.