Collaborative Research: RUI: The Evolution of Life History, Physiological, and Floral Traits in Clarkia: do Genetic Correlations Affect Mating System Evolution?

University Of St. Thomas, Saint Paul MN

Investigators

Abstract

The majority of flowering plant species rely on animals to pollinate their flowers, and in most cases such pollination results in cross-fertilization (i.e., mating between different individuals). However, nearly 25% of species regularly self-fertilize, with pollen being transferred within or between flowers on the same plant. Within natural populations, self-fertilization causes a reduction in genetic variation within individuals and their descendents, in a similar way to the effects of inbreeding in cultivated crops. Given that there are many potential ecological and evolutionary disadvantages to this loss of genetic variation, the evolution of self-fertilization in many plant species remains enigmatic. To date, most explanations for the phenomenon have proposed reproductive advantages that could outweigh the known genetic disadvantages. For example, natural selection might favor self-fertilization when pollinators are scarce or unreliable, or when short growing seasons favor rapid reproduction. However, selfing often evolves along with a suite of physiological, morphological, and life history traits, which raises the alternative possibility that its evolution is influenced by selection on other traits with which it is developmentally, physiologically, or genetically correlated. The goal of this research is to seek evidence for that alternative explanation. Specifically, using a combination of quantitative genetic and physiological approaches, the investigators will test the hypothesis that selfing can evolve as a consequence of genetic correlations between (a) floral traits that affect the rate of self-fertilization and (b) life history or physiological traits that enable plants to escape drought. If selection on life history or physiological traits does influence selfing rates, this will have cascading effects on the genetic structure of populations, potentially limiting their ability to adapt to future environmental change. The annual wildflower genus Clarkia (Onagraceae) provides a rich opportunity to investigate such effects because it includes several species in which self-fertilization has evolved independently. Broader impacts: This project will initiate a collaboration and reciprocal training among four PIs and include the participation of at least 15 undergraduates, including those of under-represented groups. PIs will work with the University of California, Santa Barbara's "Kids in Nature" program to integrate research and education. In addition, physiological comparisons between species and subspecies may generate predictions about changes in species' distributions and the genetic risks associated with inbreeding in the face of an increasing frequency of droughts that the southern Sierra Nevada is expected to experience in coming years.