Biology subjects

Bell, K. L.

Publications and source records attributed to Bell, K. L..

5 recordsLinked to original sources

bioRxiv2026

Urban enrichment of molestus ancestry and opposing temperature clines in a metropolitan Culex pipiens hybrid zone

Hybridization between ecologically distinct lineages can fuel rapid adaptation when introgressed alleles are locally favored. The North American Culex pipiens assemblage, a principal West Nile virus vector east of the Mississippi, comprises three lineages---temperate Cx. pipiens f. pipiens, urban-specialist Cx. pipiens f. molestus, and subtropical Cx. quinquefasciatus---that meet in a mid-Atlantic hybrid zone where temperature and urbanization gradients intersect. Using whole-genome Pool-seq of 24 field populations and three lineage-reference pools across the Baltimore--Washington corridor, we find a weakly differentiated, Cx. pipiens f. pipiens-like background, richer in molestus- and quinquefasciatus-like ancestry toward the warmer end of the corridor. Urbanization impacts allele frequencies across the genome: molestus-like ancestry rises with impervious surface, independently of temperature and position, while Cx. quinquefasciatus-like ancestry does not. An 11.6 Mb chromosome 3 inversion is molestus-like in every population, most of all in urban ones, and tracks genome-wide molestus-like ancestry. Temperature acts locus by locus. On chromosome 1, a cluster of six CYP6 paralogs, a family implicated in insecticide resistance and thermal-stress response, shows rising Cx. quinquefasciatus-like ancestry and read depth with temperature. A chromosome 2 interval centered on a Yan ortholog, a repressor of cell differentiation, shows non-quinquefasciatus ancestry increasing with temperature, consistent with selection against Cx. quinquefasciatus-like introgression. Urban populations therefore carry more ancestry from the human-commensal lineage, while temperature moves ancestry both ways at individual loci. Both molestus and Cx. quinquefasciatus donors carry human-contact traits, so these patterns bear on how warming and urbanization will reshape arboviral risk.

genomics↗

bioRxiv2025

Allochronic isolation between sympatric populations of an alpine butterfly

The role of isolation by distance in contributing to population structure across space is well understood, and the same principles should operate over time. Allochrony, the isolation of populations due to separation in time, can be a source of genetic differentiation, but remains infrequently documented between yearly asynchronous populations. In this study, we investigate divergence between two putative sympatric populations of the alpine butterfly Oeneis chryxus ivallda at Castle Peak, CA, USA. We find clear genetic differentiation between butterflies collected in odd and even years, with limited instances of admixture. The observed GST of 0.05 between the two populations is approximately equivalent to 26 km based on pairwise GST values observed between O. chryxus populations across space. These results demonstrate a potential source of population differentiation in systems that promote prolonged development, often found in high-elevation and high-latitude environments.

evolutionary biology↗

bioRxiv2024

Extensive admixture among karst-obligate salamandersreveals evidence of recent divergence and gene exchangethrough aquifers

Karst ecosystems often contain extraordinary biodiversity, but the complex underground aquifers of karst regions present challenges for assessing and conserving stygobiont diversity and investigating their evolutionary history. We examined the karst-obligate salamanders of the Eurycea neotenes species complex in the Edwards Plateau region of central Texas using population genomics data to address questions about population connectivity and the potential for gene exchange within the underlying aquifer system. The Eurycea neotenes species complex has historically been divided into three nominal species, but their status, and spatial extent of species ranges, have remained uncertain. We discovered evidence of extensive admixture within the species complex and with adjacent lineages. We observed relatively low levels of differentiation among all sampling localities which supports the hypothesis of recent divergence. Nominal taxonomy, aquifer region and geography accounted for a modest amount of the overall population genomic variation, but these predictors were largely collinear and difficult to disentangle. Importantly, the taxonomy of the three nominal species does not reflect the admixture apparent in clustering analyses. Inference of migration events revealed a complex pattern of gene exchange, suggesting that Eurycea salamanders have a dynamic history of dispersal through the aquifer system. These results highlight the need for greater understanding of how stygobiont populations are connected via dispersal and gene exchange through karst aquifers.

evolutionary biology↗

bioRxiv2024

Interpretable and predictive models to harness the life science data revolution

The proliferation of high-dimensional data in ecology and evolutionary biology raises the promise of statistical and machine learning models that are highly predictive and interpretable. However, high-dimensional data are commonly burdened with an inherent trade-off: in-sample prediction of outcomes will improve as additional variables are included in the model, but this may come at the cost of poor predictive accuracy and limited generalizability for future or unsampled observations (out-of-sample prediction). To confront this problem of overfitting, sparse models can focus on key variables by correctly placing low weight on unimportant variables. We competed nine methods to quantify their performance in variable selection and prediction using simulated data with different sample sizes, numbers of variables, and strengths of effects. Overfitting was typical for many methods and simulation scenarios. Despite this, in-sample and out-of-sample prediction converged on the true predictive target for simulations with more observations, larger causal effects, and fewer variables. Accurate variable selection to support process-based understanding will be unattainable for many realistic sampling schemes in ecology and evolution. We use our analyses to characterize data attributes for which statistical learning is possible, and illustrate how some sparse methods can achieve predictive accuracy while mitigating and learning the extent of overfitting.

genomics↗

bioRxiv2022

Assessing risk for butterflies in the context of climate change, demographic uncertainty, and heterogenous data sources

AbstractOngoing declines in insect populations have led to substantial concern and calls for conservation action. However, even for relatively well-studied groups, like butterflies, information relevant to species-specific status and risk is scattered across field guides, the scientific literature, and agency reports. Consequently, attention and resources have been spent on a miniscule fraction of insect diversity, including a few well-studied butterflies. Here we bring together heterogenous sources of information for 396 butterfly species to provide the first regional assessment of butterflies for the 11 western US states. For 184 species, we use monitoring data to characterize historical and projected trends in population abundance. For another 212 species (for which monitoring data are not available, but other types of information can be collected), we use exposure to climate change, development, geographic range, number of host plants, and other factors to rank species for conservation concern. A phylogenetic signal is apparent, with concentrations of declining and at-risk species in the families Lycaenidae and Hesperiidae. A geographic bias exists in that many species that lack monitoring data occur in more southern states where we expect that impacts of warming and drying trends will be most severe. Legal protection is rare among the taxa with the highest risk values: of the top 100 species, one is listed as threatened under the US Endangered Species Act and one is a candidate for listing. Among the many taxa not currently protected, we highlight a short list of species in decline, including Vanessa annabella, Thorybes mexicanus, Euchloe ausonides, and Pholisora catullus. Notably, many of these species have broad geographic ranges, which perhaps highlights a new era of insect conservation in which small or fragmented ranges will not be the only red flags that attract conservation attention.

ecology↗