Dr Kate Ostevik: “Lessons from California’s Flora Diversity”

California’s extraordinary floral diversity provides an opportunity to understand the processes that generate and maintain biodiversity. In the Ostevik lab, we study plant diversification through two complementary lenses: adaptation and speciation. I will highlight ongoing projects that illustrate both. First, I will discuss adaptation to drought in wild sunflower (Helianthus annuus). In a common-garden experiment, populations from more arid regions of California flower early. This is consistent with a drought-escape strategy, and this seems to have trade-offs with drought avoidance and tolerance. A resurrection experiment comparing ancestral and contemporary populations similarly reveals a shift toward earlier flowering under increasingly dry conditions that has consequences for interactions with other species. Second, I will discuss a putative case of homoploid hybrid speciation in southern California Penstemon. Penstemon clevelandii is reproductively isolated from both parental species, P. spectabilis and P. centranthifolius. Further, although the parents are also strongly reproductively isolated, genomic evidence suggests that hybridization between them contributed to the formation of P. clevelandii. However, P. clevelandii is not a simple 50:50 mixture of the parental genomes. Instead, our results are more consistent with introgressive speciation. Determining whether this introgression directly contributed to the evolution of reproductive barriers will require further work.