Phylogenetic and Evolutionary Inference in the Collomia-Navarretia Clade (Polemoniaceae)

Brigham Young University, Provo UT

Investigators

Abstract

Research by Dr. Leigh Johnson at Brigham Young University focuses on a group of about 50 species of annual plants that belong to the phlox family (Polemoniaceae). Several species in the genera of Collomia and Navarettia have very limited distributions and are listed as "species of concern" on federal or individual state conservation lists. Preliminary investigation of these species shows two unexpected patterns: substantial morphological divergence with little genetic divergence between two major subsets of species, and substantial genetic divergence with almost no morphological divergence between populations of what have been considered to be the same species. The factors and processes that cause discordance between morphological and genetic divergence are poorly understood in general. This group provides a model for investigating these processes, which are fundamental to understanding the nature of plant diversity and making informed decisions in species management efforts. The research proposed encompasses several thrusts: 1) Determining phylogenetic relationships among the species to provide a solid framework for addressing questions of morphological and genetic divergence. This will be accomplished from comparative analyses of DNA sequence variation from multiple genes, and analyzing the plants morphologically. 2) Revising the taxonomy of the group based on the information learned, and constructing identification keys for use by specialists and laypersons that encounter these species. 3) Testing hypotheses of discordance between morphology and genetic divergence using DNA sequence variation and morphological variation mentioned above, and examining a specific hypothesis of genetic control that may contribute to this discordance. 4) Assessing correlations between morphological features associated with reproduction and the degree of species rarity to see if predictions of rarity can be made based on such features. A methodological approach that uses both morphology and DNA sequence data is being followed to maximize the information available to characterize the diversity of these species. Because species are the basic units of conservation in plants, understanding the relationship between morphological variation, molecular variation, and rarity is important for conservation decisions. This research addresses the need for such information in an educational setting that includes research university faculty, post-doctoral students, graduate students, and undergraduate students in a mentored learning environment. Effort is being made to include persons from underrepresented groups within this research environment. An essential collaborative tie has also been established with researchers from Argentina that will facilitate fieldwork in that country as well as co-authorship of publications. In addition to anticipated peer-reviewed publication of this work, the PI will be author or co-author of taxonomic treatments of these species for several identification manuals, such as the Flora of North America, that are intended for non-specialists as well as specialists. General information on species biology and identification will be made freely available from the Tree of Life web site on the internet.