Biology subjects

Forister, M.

Publications and source records attributed to Forister, M..

12 recordsLinked to original sources

bioRxiv2026

Genomic offset is not predictive of recent demographic trends in Lycaeides butterflies

Genomic offset (GO) is increasingly used to predict population maladaptation risk under climate change, with larger offsets assumed to indicate greater vulnerability. Despite rapid adoption in conservation planning, it remains unclear how sensitive GO estimates are to key methodological choices, including SNP set composition, genotype-environment association (GEA) methods, and the specific GO metric used. Empirical validation against observed population dynamics also remains limited. Here, we evaluate the methodological robustness and predictive performance of GO using multidecadal demographic monitoring data from Lycaeides butterflies, a system with short generation times and high fecundity that may facilitate rapid adaptive responses. GO estimates were broadly consistent across SNP sets, regardless of composition or size, with climate-associated and randomly selected SNPs yielding largely concordant values. Consistency across GEA methods was moderate and depended on the SNP set used. In contrast, GO metrics differed substantially in the magnitude of maladaptation estimated, suggesting they capture distinct biological signals and should not be treated as interchangeable. Crucially, GO was a poor predictor of observed population trends, regardless of SNP set composition, GO metric, or GEA method, both at sites used to fit GEA models and when extrapolated to independent demographic sites. These findings suggest that, while GO provides a valuable conceptual framework for assessing potential maladaptation, its quantitative estimates and predictive power are sensitive to methodological choices and species-specific biological context. We therefore urge careful alignment of GO metric assumptions with conservation objectives, along with rigorous empirical validation, before GO estimates are used to inform management decisions.

evolutionary biology↗

bioRxiv2025

Temporal dynamics of color polymorphism and hybridization in Colias butterflies

Investigations into the genetic basis of color polymorphism have played a key role in our understanding of genetic architecture and the evolution of mating systems. Sulphur butterflies (Colias) have been models in this field, but also contain unsolved puzzles with respect to species boundaries and hybridization. We surveyed genomic variation across five years in a location where phenotypic intermediates between Colias eurytheme and C. eriphyle are observed, but ancestry variation of potential hybrids has not been quantified. Our results reveal individuals with hybrid ancestry roughly in proportion to the frequency of individuals of intermediate phenotype recorded in the wild. Individuals with hybrid ancestry were predominantly those with intermediate morphologies, but morphologically intermediate individuals were not always of hybrid origin, which raises alternative possibilities for the origin and maintenance of color variation in the system. Genomic regions differentiated between species are largely located on the Z chromosome, and we find more candidates on autosomes than in another Colias contact zone. The dynamics of hybridization in this system are highly variable through time, suggesting fertile avenues for future study into the maintenance of species boundaries in the face of temporally-variable, climatically influenced, and pervasive hybridization.

evolutionary biology↗

bioRxiv2025

Temporal occupancy distributions reveal multifaceted and heterogeneous effects of climatic variation on montane butterflies

Climate change has substantially altered the phenology of many organisms, with profound implications for biodiversity and species interactions. However, phenological studies of insects have often focused on shifts over time, without explicitly examining how climate drives these changes. In addition, the metrics used to measure changes in phenology often capture only limited information about the flight period. In this study, we analyzed multidecadal observational and climate data using a hierarchical Bayesian framework to model the annual probability of occurrence distributions for 135 butterfly species across five montane sites along an elevational gradient. Our analysis used polynomial models that account for shifts in abundance and the timing and length of flight periods to investigate the effect of climate on butterfly phenology. We found that spring maximum and minimum temperatures, as well as winter precipitation, are important predictors of butterfly phenology. High winter precipitation delayed phenology at high-elevation sites where substantial snowfall occurs, while increased spring maximum temperatures generally advanced phenology across all elevations. Even modest increases in spring minimum temperatures caused substantial shift in phenology. We documented variability in the effect of climate on phenology across sites, among species within a site and among populations of the same species across different sites with variability among species within a site being especially pronounced. We also found that climate influences different aspects of the flight period differently (e.g., timing versus duration), underscoring the need to move beyond single metrics such as day of first flight. These findings highlight the importance of examining the entire flight period and considering the interplay of species-specific traits to improve predictions of how climate change impacts phenology. Such approaches might be essential for designing more targeted and effective conservation strategies in response to ongoing climate change.

ecology↗

bioRxiv2024

Climate, weather, and geography shape seed mass variation and decline across western North America

Seeds are an essential reproductive strategy for most plants, and seed mass is predicted to respond to environmental factors, but we do not know if climate change-related size changes observed in other organisms will also be reflected in seed mass. We investigated the temporal, geographic, and environmental patterns that influence seed mass across 2,800 species of native plants from over 13,000 populations across the western US using information from two decades of collections from a national program, Seeds of Success. Most species exhibited low variation in seed mass, though some varied by up to 220% over their occupied area. Measures of climate change influenced seed mass in over 40% of species, which could be evidence of adaptation to new optimal values or maladaptive responses. Species with the most variation in seed mass were those collected across sites with a wide range of minimum temperatures, from more northern latitudes, and across a wide range of dates, and seeds were generally larger in areas where it was wetter and warmer. Seed mass declined for over half (55%) of species, and declined overall by an average of 0.012 mg each year, though there were many species-specific differences, including 17% of species increasing appreciably in mass. Relationships between seed mass and environmental variables varied widely in strength, identity, and direction among species, including those that often co-occur. These results support the need to continue native seed collections for conservation and restoration, as plant reproductive strategies may be shifting with changing climates.

ecology↗

bioRxiv2022

Agricultural margins could enhance landscape connectivity for pollinating insects across the Central Valley of California, U.S.A.

One of the defining features of the Anthropocene is eroding ecosystem services as a function of decreases in biodiversity and overall reductions in the abundance of once-common organisms, including many insects that play innumerable roles in natural communities and agricultural systems that support human society. It is now clear that the preservation of insects cannot rely solely on the legal protection of natural areas far removed from the densest areas of human habitation. Instead, a critical challenge moving forward is to intelligently manage areas that include intensively farmed landscapes, such as the Central Valley of California. Here we attempt to meet this challenge with a tool for modeling landscape connectivity for insects (with pollinators in particular in mind) that builds on available information including lethality of pesticides and expert opinion on insect movement. Despite the massive fragmentation of the Central Valley, we find that connectivity is possible, especially utilizing the restoration or improvement of agricultural margins which (in their summed area) exceed natural areas. Finally, we highlight steps moving forward and the great many knowledge gaps that could be addressed in the field to improve future iterations of our modeling approach.

ecology↗

bioRxiv2021

Niche specificity, polygeny, and pleiotropy in herbivorous insects

What causes host-use specificity in herbivorous insects? Population genetic models predict specialization when habitat preference can evolve and there is antagonistic pleiotropy at a performance-affecting locus. But empirically for herbivorous insects, host-use performance is governed by many genetic loci, and antagonistic pleiotropy seems to be rare. Here, we use individual-based quantitative genetic simulation models to investigate the role of pleiotropy in the evolution of sympatric host-use specialization when performance and preference are quantitative traits. We look first at pleiotropies affecting only host-use performance. We find that when the host environment changes slowly the evolution of host-use specialization requires levels of antagonistic pleiotropy much higher than what has been observed in nature. On the other hand, with rapid environmental change or pronounced asymmetries in productivity across host species, the evolution of host-use specialization readily occurs without pleiotropy. When pleiotropies affect preference as well as performance, even with slow environmental change and host species of equal productivity, we observe fluctuations in host-use breadth, with mean specificity increasing with the pervasiveness of antagonistic pleiotropy. So, our simulations show that pleiotropy is not necessary for specialization, although it can be sufficient, provided it is extensive or multifarious.

evolutionary biology↗

bioRxiv2020

Jack-of-all-trades paradigm meets long-term data: generalist herbivores are more widespread and locally less abundant

Ecological specialization is one of the most interesting and perplexing attributes of biological systems. While certain macroecological patterns, such as an increase in specialization at lower latitudes, have long been subjects of investigation, there is much yet to be learned about inter-specific variation in specialization within diverse communities. High levels of specialization have been documented for some dominant ecological interactions, such as parasitism and herbivory, but much less is known about the relative abundance of specialists and generalists within those broad functional groups. We examine untested assumptions about the positive association between local abundance and dietary specialization using a 17-year dataset of caterpillar-plant interactions in Ecuador. Our long-term data consist of experimental verification of caterpillar-plant associations and include standardized plot-based samples as well as general, regional collections of caterpillars, allowing for investigations across spatial scales and using different indices of abundance for 1,917 morphospecies of Lepidoptera ("caterpillars") from 33 families. We find that more specialized caterpillars are locally more abundant than generalists, consistent with a key component of the "jack of all trades, master of none" hypothesis, which has otherwise received poor to mixed support from previous studies that have mostly involved fewer species and shorter time series. At larger scales, generalists achieve greater prevalence across the landscape, and we find some evidence for geographic variation in the abundance-diet breadth relationship, in particular among elevational bands. Interspecific variation in abundance had a negative relationship with diet breadth, with specialists having more variable abundances across species. The interesting result that more specialized species can be both rare and common highlights the ecological complexity of specialization. Statement of authorshipCS wrote the first draft of the manuscript. DMS, MLF and LAD contributed substantially to consequent drafts and revisions. LAD, TRW, SV and DMS collected field data. CS, MLF and LAD generated research questions and designed statistical analyses. CS, DMS, LAD and MLF conducted statistical analyses. Data statementData supporting the results and conclusions can be found on a website caterpillars.org. Statistical analyses supporting the results are available upon request.

ecology↗

bioRxiv2020

Leveraging biological complexity to predict patch occupancy in a recent host range expansion

Specialized plant-insect interactions are a defining feature of life on earth, yet we are only beginning to understand the factors that set limits on host ranges in herbivorous insects. To understand the colonization of alfalfa by the Melissa blue butterfly, we quantified arthropod assemblages and plant metabolites across a wide geographic region, while controlling for climate and dispersal inferred from population genomic variation. The presence of the butterfly is successfully predicted by direct and indirect effects of plant traits and interactions with other species. Results are consistent with the predictions of a theoretical model of parasite host range in which specialization is an epiphenomenon of the many barriers to be overcome rather than a consequence of trade-offs in developmental physiology. One sentence summaryThe formation of a novel plant-insect interaction can be predicted with a combination of biotic and abiotic factors, with comparable importance revealed for metabolomic variation in plants and interactions with mutualists, competitors and enemies.

ecology↗

bioRxiv2019

Recent hybrids recapitulate ancient hybrid outcomes

Genomic outcomes of hybridization depend on selection and recombination in hybrids. Whether these processes have similar effects on hybrid genome composition in contemporary hybrid zones versus ancient hybrid lineages is unknown. Here we show that patterns of introgression in a contemporary hybrid zone in Lycaeides butterflies predict patterns of ancestry in geographically adjacent, older hybrid populations. We find a particularly striking lack of ancestry from one of the hybridizing taxa, Lycaeides melissa, on the Z chromosome in both the old and contemporary hybrids. The same pattern of reduced L. melissa ancestry on the Z chromosome is seen in two other ancient hybrid lineages. More generally, we find that patterns of ancestry in old or ancient hybrids are remarkably predictable from contemporary hybrids, which suggests selection and recombination affect hybrid genomes in a similar way across disparate time scales and during distinct stages of speciation and species breakdown.

evolutionary biology↗

bioRxiv2019

A winner in the Anthropocene: changing host plant distribution explains geographic range expansion in the gulf fritillary butterfly

O_LIThe changing climate is altering the geographic distributions of species around the world with consequences for population dynamics, resulting in winners and losers in the Anthropocene.\nC_LIO_LIAgraulis vanillae, the gulf fritillary butterfly, has expanded its range in the past one hundred years in the western United States. We combine time series analysis with species distribution modeling to investigate factors limiting the distribution of A. vanillae and to predict future shifts under warming scenarios.\nC_LIO_LIIn the western US, where we have time series and geographic data, urban development has a positive influence (the host plant is an ornamental in gardens), being associated with year of colonization. Colonization was also associated to a lesser extent with winter maximum temperatures, while a negative impact of minimum temperatures and precipitation was apparent on population growth rates.\nC_LIO_LIAcross the country, the butterfly is primarily limited by host availability and positively affected by human presence. Perhaps counter-intuitively for a largely tropical ectotherm, current effects of a warming climate (in the years post-colonization) are either negative (on population growth rate) or indirect, likely mediated through availability of areas that can support the host.\nC_LIO_LIUnder future climate scenarios, conditions are predicted to become more suitable for Passiflora in many urban areas, which would likely result in further expansion of A. vanillae during the dispersive season. These results illustrate the value of combining time series with spatial modeling to understand and predict shifting geographic ranges in the Anthropocene.\nC_LI

ecology↗

bioRxiv2019

Ecosystem services at risk from declining taxonomic and interaction diversity in a tropical forest

Reports of biodiversity loss have increasingly focused on the abundance and diversity of insects, but it is still unclear if substantive insect diversity losses are occurring in intact low-latitude forests. We collected 22 years of plant-caterpillar-parasitoid data in a protected tropical forest and found reductions in diversity and density of these insects that appear to be partly driven by a changing climate and weather anomalies. The decline in parasitism represents a reduction in an important ecosystem service: enemy control of primary consumers. The consequences of these changes are in many cases irreversible and are likely to be mirrored in nearby forests; overall declines in the region will have negative consequences for surrounding agriculture. The decline of important tropical taxa and associated ecosystem function illuminates the consequences of numerous threats to global insect diversity and provides additional impetus for research on tropical diversity.

ecology↗

bioRxiv2019

Genomic evidence of genetic variation with pleiotropic effects on caterpillar fitness and plant traits in a model legume

Plant-insect interactions are ubiquitous, and have been studied intensely because of their relevance to damage and pollination in agricultural plants, and to the ecology and evolution of biodiversity. Variation within species can affect the outcome of these interactions, such as whether an insect successfully develops on a plant species. Whereas specific genes and chemicals that mediate these interactions have been identified, studies of genome-or metabolome-wide intraspecific variation might be necessary to better explain patterns of host-plant use and adaptation often observed in the wild. Here, we present such a study. Specifically, we assess the consequences of genome-wide genetic variation in the model plant Medicago truncatula for Lycaeides melissa caterpillar growth and survival (i.e., larval performance). Using a rearing experiment and a whole-genome SNP data set (>5 million SNPs), we show that polygenic variation in M. truncatula explains 9-41% of the observed variation in caterpillar growth and survival. We detect genetic correlations among caterpillar performance and other plant traits, such as structural defenses and some anonymous chemical features; these genetic correlations demonstrate that multiple M. truncatula alleles have pleiotropic effects on plant traits and caterpillar growth or survival (or that there is substantial linkage disequilibrium among loci affecting these traits). We further show that a moderate proportion of the genetic effect of M. truncatula alleles on L. melissa performance can be explained by the effect of these alleles on the plant traits we measured, especially leaf toughness. Taken together, our results show that intraspecific genetic variation in M. truncatula has a substantial effect on the successful development of L. melissa caterpillars (i.e., on a plant-insect interaction), and further point toward traits mediating this genetic effect.

evolutionary biology↗