DISSERTATION RESEARCH: Foliar and floral evolution in geographic context: cryptic evolution in the mycoheterotrophic Pyrola picta species complex (Ericaceae)

Rancho Santa Ana Botanic Garden, Claremont CA

Investigators

Abstract

Species in genus Pyrola section Scotophylla (part of the Heath family) grow in western North America and possess several intriguing life history attributes that vary among species and will be investigated for this study. These include a special strategy for retrieving nutrition directly from fungi (i.e., mycoheterotrophy), leaves that range from large and photosynthetic to minute and non-functional, and flowers that are buzz-pollinated by bumble bees yet retain the ability to self-pollinate in the absence of bees. At least two findings complicate our general understanding of how species in section Scotophylla achieved (and maintain) reproductive isolation. First, the identification of cryptic species within the complex suggests that different genetic lineages have converged on a very similar form. Second, hybridization among species has been detected at low frequencies in populations where species co-occur. In order to understand how gene flow relates to speciation and morphological diversity, this study focuses on the phylogeography (i.e., mapping geographic and genetic lineage histories) of section Scotophylla using DNA sequence information from plants across revised species ranges. Additionally, this study focuses on (1) understanding how mixed-mating systems contribute to gene flow and species diversity, (2) determining the causes of breakdown in reproductive isolation, and (3) understanding how timing in development has played a role in the evolution of leaf morphology, anatomy, and function in this mycoheterotrophic plant lineage. This study will provide a revision of geographic ranges for species in section Scotophylla, the description of a new, cryptic species, and a contribution to ongoing discourse concerning how the recognition of cryptic species affects our interpretation of biological diversity. As fundamental, symbiotic elements of mature forest communities, mycoheterotrophic taxa like Pyrola serve effectively as indicators of ecosystem health, ultimately making ecology and evolution more accessible to a range of audiences. Understanding the evolutionary history of Pyrola lineages through time may ultimately change peoples? perceptions of both natural history and ongoing efforts by conservation biologists in western North America. Findings from this study will be available in peer-reviewed journals, at scientific conferences and in non-scientific forums, and as interpretive literature for students and teachers interested in natural history.