Partially fertile, interspecific hybrids of mosses can serve as a model for studying gene flow between parent species. The bryophyte (moss, liverworts and hornworts) life cycle, in which both diploid and haploid generations are well developed, provides an excellent system in which to document interspecific hybridization in the diploid generation through genetic analysis of the resulting recombinant gametophytes in the haploid generation. This investigation of gene flow will focus on two closely related species of Sphagnum moss (Sphagnum macrophyllum and S. cribrosum). The amount of reproductive isolation between closely related species can be determined through genetic analyses of the recombinant gametophytes produced by their partially fertile, interspecific hybrids. Samples will be collected throughout their ranges where the two species occur together and where they do not. The recent discovery of a site where gametophytes of both species are intimately intermixed provides an exceptional opportunity to test for gene flow between species under circumstances where it is most likely to occur. Gene flow in the samples will be evaluated using DNA markers in extremely variable stretches of the genome. Data analyses will test newly advanced coalescence models in population genetics that involve population size and migration rates. This study will improve our understanding of the evolutionary history of this ecologically and economically important group of mosses. In addition, it will also lead to a better understanding of the complex processes involved in speciation. This award provides the student investigator opportunities to enhance his doctoral dissertation study and share his discoveries with others.
