Biology subjects

Betancourt, N. J.

Publications and source records attributed to Betancourt, N. J..

3 recordsLinked to original sources

bioRxiv2024

Pervasive fitness trade-offs revealed by rapid adaption in large experimental populations of Drosophila melanogaster

Trade-offs are an inherent feature of organismal biology that are expected play a fundamental role in the evolution of natural populations. Efforts to quantify trade-offs are largely confined to phenotypic measurements and the identification of negative genetic-correlations among fitness-relevant traits. Here, we use time-series genomic data collected during experimental evolution in large, genetically diverse populations of Drosophila melanogaster to directly measure the manifestation of trade-offs in response to fluctuating selection on ecological timescales. Specifically, we first conducted a lab-based selection experiment to quantify a genome-wide signal of antagonistic pleiotropy elicited in response to shifting population densities and associated with reproduction and stress tolerance selection. In doing so, we identified a putative role of two cosmopolitan inversions in these trade-offs. We then conducted an independent experiment to show that a simple manipulation of increasing population density under controlled lab-based conditions identified loci that are relevant to selection during population expansion and collapse in a complex, semi-natural setting. In concert, our results reveal how adaptation in complex, natural environments can be coarse-grained in such a manner to drive repeatable and predictable patterns of genomic variation, and further add credence to models positing a role of generic fitness trade-offs in the maintenance of variation in natural populations.

evolutionary biology↗

bioRxiv2024

Drosophila melanogaster pigmentation demonstrates adaptive phenotypic parallelism but genomic unpredictability over multiple timescales

Populations are capable of responding to environmental change over ecological timescales via adaptive tracking. However, the translation from patterns of allele frequency change to rapid adaptation of complex traits remains unresolved. We used abdominal pigmentation in Drosophila melanogaster as a model phenotype to address the nature, genetic architecture, and repeatability of rapid adaptation in the field. We show that D. melanogaster pigmentation evolves as a highly parallel and deterministic response to shared environmental gradients across latitude and season in natural North American populations. We then experimentally evolved replicate, genetically diverse fly populations in field mesocosms to remove any confounding effects of demography and/or cryptic structure that may drive patterns in wild populations; we show that pigmentation rapidly responds, in parallel, in fewer than fifteen generations. Thus, pigmentation evolves concordantly in response to spatial and temporal climatic gradients. We next examined whether phenotypic differentiation was associated with allele frequency change at loci with established links to genetic variance in pigmentation in natural populations. We found that across all spatial and temporal scales, phenotypic patterns were associated with variation at pigmentation-related loci, and the sets of genes we identified in each context were largely nonoverlapping. Therefore, our findings suggest that parallel phenotypic evolution is associated with distinct components of the polygenic architecture shifting across each environmental gradient to produce redundant adaptive patterns.

evolutionary biology↗

bioRxiv2021

Direct observation of adaptive tracking on ecological timescales in Drosophila

Direct observation of evolution in response to natural environmental change can resolve fundamental questions about adaptation including its pace, temporal dynamics, and underlying phenotypic and genomic architecture. We tracked evolution of fitness-associated phenotypes and allele frequencies genome-wide in ten replicate field populations of Drosophila melanogaster over ten generations from summer to late fall. Adaptation was evident over each sampling interval (1-4 generations) with exceptionally rapid phenotypic adaptation and large allele frequency shifts at many independent loci. The direction and basis of the adaptive response shifted repeatedly over time, consistent with the action of strong and rapidly fluctuating selection. Overall, we find clear phenotypic and genomic evidence of adaptive tracking occurring contemporaneously with environmental change, demonstrating the temporally dynamic nature of adaptation. One sentence summaryRapid environmental change drives continuous phenotypic and polygenic adaptation, demonstrating the temporal dynamism of adaptation.

evolutionary biology↗