Dimensions: Diversity and constraint in the germination niche: Implications for persistence in a biodiversity hotspot

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In an uncertain world, timing is everything. For plants, the timing of seed germination determines whether individuals will survive and reproduce. The timing of germination also influences whether populations can persist in particular environments. Many plants use cues such as temperature, day length, and soil moisture to time germination during favorable conditions. Species differences in these cues may thus determine the climatic conditions in which a species can persist. In turn, these differences can shape their distribution across the landscape. How do responses of these cues evolve? Will they continue to evolve if the environment changes? How do these patterns determine species persistence and distribution under current and future conditions? The research team will address these questions in Mediterranean climates within the California Floristic Province (CFP). The CFP is a biodiversity hotspot characterized by strong climate variability. This research will investigate how germination responses to environmental cues have evolved in a group of native CFP wildflower species. To do so, the team will use a combination of greenhouse experiments, genomic studies, and comparative analyses. The project will use data from historical collections and develop models to understand how these processes shape the distribution of these species across the CFP. The results will contribute a deeper understanding of how responses to environmental cues shape plant life cycles. This will provide insight into the forces driving trait evolution, population persistence, and species distributions. As part of the activities, three postdoctoral scholars, a graduate student, and several undergraduate students will receive research training and mentorship. The research team will investigate functional, genetic, and phylogenetic diversity of germination timing in the Streptanthus (jewelflower) group. First, the research team will characterize germination responses to temperature and moisture across the group. Second, they will identify candidate genes and pathways that drive these differences in responses. Next, they will determine the consequences of those patterns for individual fitness. They will assess how those patterns have evolved across the group and evaluate possible constraints to past and future evolution. Finally, a process-based model that integrates these mechanisms into predictions of life history timing across a range of environmental conditions will be developed. This new model will be incorporated into existing demographic models for predicting population persistence and species distributions. Together, this research integrates three dimensions of biodiversity- functional diversity in traits driving life history responses to cues; genomic variation underlying that diversity, and divergence and constraint across the Streptanthus clade- to understand the evolution of the life history timing, and how variation in responses to environmental cues will influence the ecological function of population persistence and species distributions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.