RUI: Collaborative Research: The Cenozoic radiation of eupolypod ferns: did selection for drought tolerance drive the evolutionary physiology of sporophytes and gametophytes?

Colgate University, Hamilton NY

Investigators

Abstract

Seed-free vascular plants such as ferns are the second most diverse plant lineage after the flowering plants, yet given their two-stage lifecycle and apparent intolerance of drought, the bases of their continued success are not completely understood. Recent studies have shown that both fern fronds (the vegetative generation) and fern gametophytes (the sexual generation) have evolved numerous strategies to cope with and recover from severe drought stress. This research investigates the water relations of both stages of the fern lifecycle to test the hypothesis that the evolution of traits typically related to drought tolerance promoted the expansion of ferns from largely moist, terrestrial habitats to drier, sunnier canopy habitats. The research will focus on drought tolerant traits of two recent fern lineages, which represent the bulk of tropical fern species diversity. Physiological, morphological and anatomical attributes will be examined across select species in the field and in the laboratory. This basic research will not only expand knowledge of the processes that shape biological diversity, but also potentially identify novel plant traits that could assist with the development of more drought resistant agricultural species. Students will receive international research experiences in Mexico and Costa Rica, and student/instructor exchanges will promote research collaboration. Outreach activities to the public will combine with non-profit collaborators at the Save the Redwood League and the Southern Madison Heritage Trust to illustrate the important role of ferns and other non-vascular plants in the ecology of natural plant communities. In order to determine whether drought stress exerts strong, convergent selection pressure on fern sporophytes and gametophytes, this research will examine the desiccation tolerance of gametophytes from numerous species in the Pteridaceae. The Pteridaceae are a hyper-diverse family of ferns that are ancestral to the Eupolypods, and the results from this study will complement an existing data set documenting drought tolerance in the Pteridaceae sporophytes. A second set of studies will examine the drought tolerance of epiphytic and terrestrial Eupolypod sporophytes. Experiments will test resistance to hydraulic failure by drought-induced air entry, leaf turgor loss points, and relate these data to numerous anatomical and morphological traits. Lastly, complementary studies looking at the desiccation tolerance of gametopytes in this group will be conducted. The results will be analyzed in a phylogenetic framework, which will explicitly test for correlated trait evolution in both sporophytes and gametophytes.