Seedless vascular plants such as ferns and horsetails are among the oldest lineages in the modern flora and with origins in the Devonian, it is remarkable that these plants remain competitive in a world dominated by conifers and angiosperms. Much is known about the physiology of woody plants, but what explains the continued success of the seedless vascular group? The goal of the proposed research is to examine the ferns and fern allies through the lens of physiology, specifically plant water relations. Efficient and resilient water transport is critical for plant success, but whether water transport played a role in the evolutionary physiology of seedless vascular flora remains unknown. The proposed research has several objectives with the overarching goals focusing on the relationships between species' drought resistance, vascular anatomy, habitat and life history traits, and how these features bear on the evolution of early vascular flora. Anatomical and physiological data will be incorporated into a realistic model of fern water transport, the results of which will be used to inform a large-scale sampling effort across the well-resolved evolutionary tree of ferns. This will improve present understanding of the manner in with which specific traits facilitated deep-time diversification of the ferns and fern allies. Lastly, this project will apply a recently developed model of vascular design to seedless vascular plants, and thus complete the understanding of the selection pressures driving the evolution of transport networks across all vascular flora. Broader impacts include high school and undergraduate participation in a conservation based, long-term study of fern performance in the redwood understory, teaching modules in local under-served high schools and the mentoring of undergraduate students in the PI's lab.
