Search for: All records

Interspecific competition reduces resource availability and can affect evolution. We quantified multivariate selection in the presence and absence of strong interspecific competition using a greenhouse experiment with 35 natural accessions ofArabidopsis thaliana. We assessed selection on nine traits representing plant phenology, growth, and architecture, as well as their plasticities.Competition reduced biomass and fitness by over 98%, and plastic responses to competition varied by genotype (significant G × E) for all traits except specific leaf area (SLA). Competitive treatments altered selection on flowering phenology and plant architecture, with significant selection on all phenology traits and most architecture traits under competition-present conditions but little indication that selection occurred in the absence of competitors. Plasticity affected fitness only in competition-present conditions, where plasticity in flowering time and early internode lengths was adaptive. The competitive environment caused changes in the trait correlation structure and surprisingly reduced phenotypic integration, which helped explain some of the observed selection patterns. Despite this overall shift in the trait correlation matrix, genotypes with delayed flowering had lower SLA (thicker, tougher leaves) regardless of the competitive environment, a pattern we have not seen previously reported in the literature. Overall, our study highlights multiple ways in which interspecific competition can alter selective regimes, contributing to our understanding of variability in selection processes over space and time.

Hybridization is a common phenomenon, yet its evolutionary outcomes remain debated. Here, we ask whether hybridization can speed adaptive evolution using resynthesized hybrids between two species of Texas sunflowers (Helianthus annuusandH. debilis) that form a natural hybrid in the wild (H. annuusssp.texanus). We established separate control and hybrid populations and allowed them to evolve naturally in a field evolutionary experiment. In a final common-garden, we measured fitness and a suite of key traits for these lineages. We show that hybrid fitness evolved in just seven generations, with fitness of the hybrid lines exceeding that of the controls by 14% and 51% by the end of the experiment, though only the latter represents a significant increase. More traits evolved significantly in hybrids relative to controls, and hybrid evolution was faster for most traits. Some traits in both hybrid and control lineages evolved in an adaptive manner consistent with the direction of phenotypic selection. These findings show a causal pathway from hybridization to rapid adaptation and suggest an explanation for the frequently noted association between hybridization and adaptive radiation, range expansion, and invasion.

Early‐life conditions can have long‐lasting effects (experiential legacies) on an individual's performance. Experiential legacies are an important source of variation among mature individuals because responses to early‐life environments vary widely. Yet, the factors influencing the magnitudes and directions of phenotypic responses to experiential legacies are poorly understood, hindering our ability to predict adult phenotypes and population‐level consequences of environmental stressors. To better understand these issues, we examined how experiential legacies varied with the type of phenotypic response (e.g., reproduction, longevity), characteristics of the individual, and characteristics of the stressful conditions imposed. We conducted a meta‐analytic review (n_species = 65,n_studies = 81), examining experiential legacies of early‐life nutritional restriction. We found generally consistent negative or neutral impacts of early nutritional stress on later‐life phenotypes, indicating that positive responses to early nutritional restriction may be rare among organisms. Our results also demonstrated differences in how experiential legacies were expressed in specific dimensions of an individual's phenotype; for example, magnitude and direction differed among responses in development rate (weak negative response), offspring quality and quantity (strong negative), and longevity (neutral response). We also found that the harsher the early‐life nutritional stress, the stronger the negative nutritional legacy. Our results emphasize the complicated interactions among a suite of phenotypic responses in determining individual performance. Given the potential for individual performance to inform the demography and dynamics of populations, we offer avenues for future research that can improve our understanding of how experiential legacies of nutrition or other early‐life conditions affect populations.