Testing Adaptive Radiation Theory in Penstemon (Plantaginaceae)

Ohio State University, The, Columbus OH

Investigators

Abstract

Many groups of animals and plants are very diverse and species rich but are closely related to a group of organisms that are not diverse and are species poor. Diversification can be a slow process or a rapid one, and the dynamics of why some groups become very diverse with hundreds of species, while others have just a few is an especially relevant field of study given a dynamically changing environment. Adaptive radiation theory predicts an increase in speciation rates resulting from adaptations in response to ecological opportunity, and that speciation rates are initially high, but decrease as ecological niches fill or extinction rates increase. Several iconic groups of animals have served as testing grounds for adaptive radiation theory, but few plant studies have focused on testing predictions of the theory. Penstemon (Plantaginaceae) is the largest plant genus native to North America, with nearly 300 species, and is an excellent example of a group that had undergone rapid diversification since the Pleistocene. Penstemon, diversified rapidly, with hundreds of species, during the Pleistocene when changing climatic conditions resulted in the melting of massive ice sheets covering much of the northern hemisphere. This research will study the effect of changing environment on organisms and how they adapt to climatic niches through speciation. The project will integrate systematics and bioinformatics training for graduate students and will result in open-source bioinformatics tools and web-based biodiversity data for the general public, scientists, and educators. This project will generate next-generation sequencing data and develop novel species trees methods to test adaptive radiation theory in Penstemon. The project will generate next-generation targeted amplicon sequencing data from multiple loci, however handling the large volumes of data associated with collecting genomic data has been a technological challenge. To solve this issue the project will develop new methods of analyses to handle data sets with many taxa and large amounts of data and the project will develop a coalescent-based approach for estimating a species tree from multi-locus data. The species tree inferred will be used to examine rates of species diversification across the genus, specifically elucidating whether clades exhibit patterns consistent with those predicted by adaptive radiation theory. Morphological characters, ecological habitats, seed germination requirements, incidence of hybridization, and geographical data will be analyzed to determine if there are key innovations and/or ecological opportunities that may explain differences in speciation rates across the genus. Additionally, new methods of analyses will be developed for detecting patterns of hybridization in a genus that has a rapid rate of diversification.