Research

1. Ecomorphology, convergence, and adaptation

How repeatable is evolution? Can macroevolutionary patterns best be described as contingent on historical events or conversely deterministic, producing similar phenotypes in a given environment? A good barometer of the repeatability of evolution is the degree to which lineages converge on similar phenotypic solutions to shared environmental pressures. Freshwater habitats, with their unique fluid dynamics, exert strong selective forces on the morphology of aquatic organisms and thus present an ideal system for testing ecomorphological hypotheses. My work uses phylogenetic comparative methods and high-throughput phenotyping to understand ecomorphological evolution of aquatic mollusks. Thus far, my collaborators and I have shown that the shells of freshwater mussels are highly convergent. In large river systems, mussels evolve thicker shells and conversely thinner shells in headwater streams. See Keogh et al. 2024 for more information.

2. Phenotypic plasticity

Globally, freshwater ecosystems are undergoing rapid environmental change due to growing anthropogenic pressures. For aquatic organisms, these complex environmental alterations represent novel physiological challenges, which they must overcome in order to survive and reproduce. One strategy to maintain resilience to environmental uncertainty is phenotypic plasticity, whereby a single genotype can develop multiple phenotypes based on environmental cues. Phenotypic plasticity has been shown to be a major biological mechanism in which organisms respond to rapidly changing environments, including climate change. My collaborators and I have ran multiple common garden and reciprocal transplant experiments to identify plastic responses of freshwater mussels. We are currently using RNAseq of transplanted mussels to try to understand the molecular pathways of plasticity. See Keogh et al. 2025 for a representative publication.

3. Speciation and biogeography

The isolated river drainages of eastern North America experienced repeated glacial expansion and recession throughout the Cenozoic, resulting in cyclical periods of coalescence and isolation between neighboring river systems. Landscape evolution mediated by climate change appears to be partially responsible for the great diversity of freshwater mussels. Phylogeography and divergence dating of multiple mussel species frequently show congruence between the timing of historical climatic fluctuations and diversification events, suggesting drainage capture and isolation have played a dramatic role in the proliferation of aquatic diversity. Concurrently, freshwater mollusks are one of the most imperiled groups of animals globally. Ongoing species delimitation and conservation genomic work, identifying new species and areas of high endemism, is critical to conserve these ecological engineers. See Keogh et al. 2025 for a representative publication.