Quantifying the roles of pollination and post-pollination barriers in flowering plant speciation: a case study of the diverse Neotropical genus Burmeistera (Campanulaceae)

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This project will investigate how flowering plants develop reproductive boundaries among species over time. Animal pollinators are critical to the reproduction and survival of most flowering plants, including many of our agricultural crops. Conventional wisdom holds that animal pollinators also have a primary role in driving the diversification of these species. However, this idea has rarely been tested in detail and at scale. Researchers will test this hypothesis using Burmeistera, a flowering plant genus whose 116 species depend on nectar-feeding bats for pollination. Burmeistera species place their pollen on different parts of the bats' heads, which may reduce the exchange of pollen and genes between species. They also have different degrees of genetic incompatibility with each other. These genetic barriers may reduce the fertilization success of cross-species pollinations or the survival of hybrid offspring. Researchers will evaluate which of these reproductive barriers contributes to each stage of the speciation process in Burmeistera. Undergraduate and graduate students, including those from underrepresented groups, will be involved in all aspects of the project and will be trained in field and laboratory techniques. The project will also support the professional development of a post-doctoral researcher. Researchers will communicate results to the public via educational displays at the Missouri Botanical Garden and bilingual field guides for Burmeistera species.This project will discover how reproductive barriers evolve during angiosperm speciation using an integrated experimental and comparative approach. Researchers will construct a robust species-level phylogeny for Burmeistera (Campanulaceae, the bell-flower family) using DNA sequence data from whole plastomes and over 700 nuclear loci. They will then measure pre- and post-pollination reproductive barriers among pairs of species having different phylogenetic distances. Assessment will include cross-pollination trials by captive nectar-feeding bats as well as hand-crosses of species in cultivation. Researchers will compare these measures within the context of the phylogeny to test the hypothesis that post-pollination reproductive barriers evolve before others. They will also determine whether changes in the length of pollen-bearing and receiving organs of Burmeistera flowers are correlated with speciation events, which would be consistent with the hypothesis of pollinator-driven speciation. Project outcomes will include an exceptionally detailed exploration of angiosperm speciation processes, improved taxonomic circumscriptions within a poorly-studied Neotropical flowering plant group, and the creation of new genetic resources and herbarium collections. The project will strengthen international research collaborations among US, Ecuadorian and Colombian scientists.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.