Biology subjects

Weis, A. E.

Publications and source records attributed to Weis, A. E..

5 recordsLinked to original sources

bioRxiv2026

The Dynamics of Long Terminal Repeat Proliferation in the Hesperis matronalis Genome

Genome sizes vary across four orders of magnitude in flowering plants, with consequences for evolution. Much of this variation is due to differences in transposable element content, particularly in long terminal repeat (LTR) retrotransposons. Despite their importance in plant genome evolution, LTRs have long been challenging to characterize because of their repetitive nature, but recent advances in sequencing allow more detailed explorations of their behavior. They are now known to occupy distinct genomic niches, and to evolve and proliferate over time as they escape host controls. In this study, we present a new genome sequence of the largest Brassicaceae genome, Hesperis matronalis, and describe its transposable element complement and how LTRs contributed to its genome expansion. We find evidence for both early proliferation of Ty3 elements and rapid recent expansion of Ty1-copia elements. In addition, we place the H. matronalis LTRs in a broader context of LTR evolution in the Brassicaceae, showing that the dominant copia families are part of an evolutionary radiation endemic to Hesperis. Finally, we describe differences in LTR age, proximity to genes, and apparent removal rate which suggest consistent genomic niches over the lifespan of a TE family. These results shed light on how LTRs evolve dynamically with host genomes, and have contributed to the expansion of the largest genome in the Brassicaceae. Significance StatementOrganisms differ in many ways, including the size of their genomes. Genome size, in turn, can affect many aspects of evolution, such as what kinds of mutations are available to natural selection and how effectively natural selection can act. The "complexity" of an organism does not predict its genome size; rather, much of this variation is explained by the amount of transposable elements, or "jumping genes," that inhabit a genome. This study describes the evolutionary history of the transposable elements in dames rocket (Hesperis matronalis), which has the largest genome of any plant in the mustard family (Brassicaceae). We find that the genome inflation in Hesperis is due to transposable elements that are not found elsewhere in the Brassicaceae, and likely diversified within Hesperis. Characterizing the evolution and behavior of transposable elements in this genome offers a better understanding of the forces that determine genome size and ultimately affect the evolution of life on earth.

genomics↗

bioRxiv2025

Longitudinal and cross-sectional selection on flowering traits in a self-incompatible annual.

Net selection on a trait reflects the association of phenotype to fitness, across an entire life cycle. This longitudinal estimate of selection can be viewed as the summation of selection episodes, each characterized by a cross-sectional estimate. Selection may be consistent in direction and strength across episodes for some traits, fluctuating in others, and for some, concentrated in a single intense event. Additionally, while selection on plant reproductive traits is predicted to be stronger through male fitness than female fitness, male fitness remains less studied. We investigated how selection on flowering traits in Brassica rapa varied temporally and spatially by measuring male reproductive fitness in four experimental populations with two spatial arrangements. To estimate longitudinal and cross-sectional selection, we introduced plants at successive intervals within a single reproductive season. We genotyped over 3000 plants and calculated selection on flowering time, duration, and total flowers. Cross-sectional analyses revealed directional selection was common, but patterns were masked by longitudinal estimates. Spatial population arrangement significantly impacted pollen movement, demonstrating how breeding timing and spatial aggregation interact to create complex evolutionary dynamics.

evolutionary biology↗

bioRxiv2022

The capacity for adaptation to climate warming in an annual plant (Brassica rapa)

The persistence of a declining population in the face of environmental change may depend on how fast natural selection restores fitness, a process called "evolutionary rescue". In turn, evolutionary rescue depends on a populations adaptive potential. Fishers theorem states that a populations adaptive potential equals the additive genetic variance for fitness (VA(W)) divided by mean fitness [Formula]. Both the numerator and denominator of this rate can differ across environments even when holding allele frequencies constant. However, little is known about how these rates change in wild populations during adaptation, including changes in additive and dominance variance. We assessed the change in adaptive potential and dominance variance in fitness (VD(W)) for a Quebec population of wild mustard (Brassica rapa) under climate warming. We also assessed adaptive constraints that could arise from negative genetic correlations across environments. We grew a pedigreed population of 7000 plants under ambient and heated (+4{degrees}C) temperatures and estimated the change in [Formula], VA(W), VD(W), and the cross-environment genetic correlations (rA). As predicted, estimates of VA(W) and adaptive potentials were higher under heated conditions but non-significantly so. This is perhaps because, surprisingly, plants exposed to a warmer climate exhibited greater [Formula]. Nevertheless, increased fitness in the warmer environment suggests a plasticity-based short-term potential for adaptation, and that weak but non-significant genetic correlations across environments will enable slow on-going adaptation to warming. Overall, this population of B. rapa harbours existing genetic architecture to persist under warmer temperatures through pre-adaptation but not through evolutionary rescue.

evolutionary biology↗

bioRxiv2017

Selection for pollen competitive ability in mixed mating systems

Co-expression of genes in plant sporophytes and gametophytes allows correlated gametic and sporophytic selection. Theory predicts that, under outcrossing, an allele conferring greater pollen competitive ability should fix within a population unless antagonistic pleiotropy with the sporophyte stage is strong. However, under strong selfing, pollen competitiveness is immaterial as superior and inferior competitors are deposited on opposite stigmas, producing assortative competition. Because many plant species have mixed-mating systems, selfing should be critical in the spread and maintenance of pollen-expressed genes affecting competitiveness. We present two one-locus, two-allele population genetic models for the evolution of a locus controlling pleiotropic antagonism between pollen competitiveness and diploid fitness. Analytical solutions provide minimum and maximum selfing rates allowing invasion of alleles with greater diploid and haploid fitness respectively. Further, polymorphism is only maintained when diploid selection is recessive. Fixation of the allele conferring greater pollen competitiveness may be prevented, even with weak sporophytic counter-selection, with sufficiently high selfing. Finally, selfing expands and limits the range of haploid-diploid selection coefficients allowing polymorphism, depending on dominance and selfing mode.

evolutionary biology↗

bioRxiv2017

Phenological responses to multiple environmental drivers under climate change: insights from a long-term observational study and a manipulative field experiment

Climate change has induced pronounced shifts in the reproductive phenology of plants, with the timing of first flowering advancing in most species. Indeed, population persistence may be threatened by the inability to track climate change phenologically. Nevertheless, substantial variation exists in biological responses to climate change across taxa. Here, we explore the consequences of climate change for flowering phenology by integrating data from a long-term observational study and a manipulative experiment under contemporary conditions. Dissecting the environmental factors that influence phenological change will illuminate why interspecific variation exists in responses to climate change. We examine a 43-year record of first flowering for six species in subalpine meadows of Colorado in conjunction with a 3-year snow manipulation experiment on the perennial mustard Boechera stricta from the same site. We analyze shifts in the onset of flowering in relation to environmental drivers known to influence phenology: the timing of snowmelt, the accumulation of growing degree days, and photoperiod. At our study site, climate change is reducing snowpack and advancing the timing of spring snowmelt. We found that variation in phenological responses to climate change depended on the sequence in which species flowered, with early-flowering species flowering faster, at a lower heat sum, and under increasingly disparate photoperiods in comparison to species that flower later in the season. Furthermore, climate change is outpacing phenological change for all species. Early snow removal treatments confirm that the timing of snowmelt governs observed trends in flowering phenology of B. stricta and that climate change can reduce the probability of flowering, thereby depressing fitness. Shorter-term studies would not have captured the trends that we document in our observational and experimental datasets. Accurate predictions of the biological responses to climate change require a thorough understanding of the specific environmental factors driving shifts in phenology.

ecology↗