Chasing the fitness optimum: temporal variation in the genetic and environmental expression of life-history traits for a perennial plant

Abstract

Background and Aims The ability of plants to track shifting fitness optima is crucial within the context of global change, where increasing environmental extremes may have dramatic consequences to life history, fitness, and ultimately population persistence. However, tracking changing conditions relies on the relationship between genetic and environmental variance, where selection may favor plasticity, the evolution of genetic differences, or both depending on the spatial and temporal scale of environmental heterogeneity. Methods Over three years, we compared the genetic and environmental components of phenological and life-history variation in a common environment for the spring perennial Geum triflorum. Populations were sourced from alvar habitats that exhibit extreme, but predictable annual flood-desiccation cycles and prairie habitats that exhibit similar, but less predictable variation in water availability. Key Results Heritability was generally higher for early life history (emergence probability) relative to later life history traits (total seed mass), indicating that traits associated with establishment are under stronger genetic control relative to later life-history fitness expressions, where plasticity may play a larger role. This pattern was particularly notable in seeds sourced from environmentally extreme, but predictable alvar habitats relative to less predictable prairie environments. Fitness landscapes based on seed source origin, largely characterized by varying water availability and flower production, described selection as the degree of maladaptation of seed source environment relative to the prairie common garden environment. Plants from alvar populations were consistently closer to the fitness optimum across all years. Annually, the breadth of the fitness optimum expanded primarily along a moisture gradient, with inclusion of more populations onto the expanding optimum. Conclusions These results highlight the importance of temporally and spatially varying selection to life history evolution, indicating plasticity may become a primary mechanism needed to track fitness for later life history events within perennial systems.

Climate and habitat type interact to influence contemporary dispersal potential in Prairie Smoke (Geum triflorum)

“…However, in prairie populations where soils are deeper and there is more access to water, the growing season may extend as degree days increase. Here, G. triflorum has more time for active growth (Kulbaba et al., 2023) and can send its seeds farther. Recent evidence examining the phenological response of G. triflorum reflects these trends, where traits associated with initial establishment are under strong genetic control, but later life‐history stages are under stronger environmental control (Kulbaba et al., 2023).…”

“…Furthermore, it is a biologically meaningful climate variable as it reflects the required heat sum associated with the onset of growth (Beaubien & Hamann, 2011). Development is predicted to be particularly sensitive to climate change (McGinn & Shepherd, 2003) as shifts in DD5 for spring perennials, such as G. triflorum , have substantial influence on the timing and duration of the growing season (Beaubien & Hamann, 2011; Kulbaba et al., 2023; Volk et al., 2022; Whittet et al., 2017). We note here that both prairie and alvar populations fell within a similar latitudinal range, therefore values of DD5 are largely independent of photoperiod (e.g., each habitat type on the whole had overlapping distributions of DD5).…”