Biology subjects

Sasser, K. T.

Publications and source records attributed to Sasser, K. T..

3 recordsLinked to original sources

bioRxiv2026

Population dynamics in extreme environments: shared histories of strong selection lead to predictable patterns across separate high-elevation populations of small mammals

Many frameworks exist to identify species that are vulnerable to environmental change, but we still generally lack the ability to anticipate species' responses when changes occur. Exploring patterns of trait evolution along environmental gradients could help this process: conditions become more predictable and less variable at the ends of gradients, with past studies hypothesizing that consistently harsh environments will result in predictable evolutionary patterns. To test this hypothesis, we characterized genetic and phenotypic variation, as well as selection on this variation, in deer mice (Peromyscus maniculatus) along two transects spanning from 2120-4200m in the Colorado Rocky Mountains, U.S.A. We found that both genetic and phenotypic variation declined with elevation, that high elevation populations had higher rates of survival, and that fewer traits influenced survival at high elevations. These results suggest extreme environments may lead to predictable consequences for populations and provide a basis for forecasting population vulnerability to environmental change.

ecology↗

bioRxiv2025

Heritable differences in metabolic stability underpin thermal tolerance of threespine stickleback (Gasterostues aculeatus) ecotypes

Understanding how organisms adapt to divergent thermal conditions can inform efforts to preserve biodiversity in a warming world. Change in aerobic scope (AS)-total energy available to perform tasks outside of homeostasis-is an ecologically relevant predictor of performance across a range of temperatures. Mathematical models suggest that the shape of AS-temperature curves should evolve depending on environmental heterogeneity, but few studies have tested whether this occurs at the intraspecific level. We examined AS-temperature associations across two ecotypes of threespine stickleback fish (Gasterosteus aculeatus), including both short- and long-term heat treatments. We predicted that fish from shallow, thermally dynamic lakes would display greater AS stability at high temperatures than residents of deep, thermally stable lakes. We also tested whether heat and AS are correlated with variation in a fibrotic immune response after exposure to the cestode Schistocephalus solidus. We found few heat-associated differences in condition or immunity, but fibrosis decreased AS. Additionally, limnetic AS declined with heat and this shift was correlated with mortality. In contrast, benthic ecotypes displayed remarkable stability in AS and survival across temperatures. Connecting intraspecific variation in AS with local thermal environments is a promising avenue for estimating, and potentially fostering, population resilience to warming climates.

evolutionary biology↗

bioRxiv2024

Destabilized host-parasite dynamics in newly founded populations

When species disperse into previously unoccupied habitats, new populations encounter unfamiliar species interactions such as altered parasite loads. Theory predicts that newly founded populations should exhibit destabilized eco-evolutionary fluctuations in infection rates and immune traits. However, to understand founder effects biologists typically rely on retrospective studies of range expansions, missing early-generation infection dynamics. To remedy this, we experimentally founded whole-lake populations of threespine stickleback. Infection rates were temporally stable in native source lakes. In contrast, newly founded populations exhibit destabilized host-parasite dynamics: high starting infection rates led to increases in a heritable immune trait (peritoneal fibrosis), suppressing infection rates. The resulting temporal auto-correlation between infection and immunity suggest that newly founded populations can exhibit rapid host-parasite eco-evolutionary dynamics.

evolutionary biology↗