Phylogenetics of Diploid and Allopolyploid Hibiscus Sect. Furcaria (Malvaceae)

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

0108231 Small One of the primary foci of the field of plant systematics is to understand the genealogical relationships among present day species, and to understand the processes that gave rise to those species. This project is focused on a group of species in the genus Hibiscus in the plant family Malvaceae (the Mallow family). This group of Hibiscus, taxonomically classified as Hibiscus section Furcaria, includes over 100 species that are distributed worldwide. Ten of these species are known to be diploid (having the "normal" two sets of chromosomes), while the remainder are polyploid having four, six, eight or ten sets of chromosomes. These polyploids are hypothesized to have originated through hybridization between two different species followed by chromosome doubling in the offspring. In this group the polyploid species are more numerous than the diploid species, perhaps due to the genetic diversity provided by the extra sets of chromosomes. The goal of this project is to first elucidate relationships among the diploid species in this group. Subsequently selected polyploid species will also be analyzed - each polyploid will contain genes from each of its parents, some of which are likely to be diagnostic, which will allow the identification of the hybridizing parents of each polyploid species. Ultimately these data will be used to address the classification of the species into taxonomic groups, to study the geographic patterns inherent in those relationships, and the evolution of morphological characters. The data to be employed in these analyses include nuclear ribosomal genes and chloroplast gene markers, as well as DNA sequences from nuclear-encoded genes of the alcohol dehydrogenase gene family. Molecular biology has provided researchers access to a wealth of genetic data, in particular DNA sequences, for analyzing relationships among species. Plant systematists have relied primarily on sequences from two sources: chloroplast DNA and nuclear ribosomal DNA, both of which are genetically tractable and easy to isolate. There is a vast resource of DNA sequences that have remained relatively untapped, however, in the rest of the plant nuclear genome. These types of sequences have been largely ignored by systematists primarily because they are more genetically complex and thus more difficult to isolate and characterize. This additional experimental effort, however, can be outweighed by the quantity and quality of data available from these sequences. Previous work by Dr. Randall Small on cotton and related species (genus Gossypium, also in the Mallow family) has shown that these types of sequences can be reliably isolated and can be exceptionally useful for systematic studies. These studies were expedited by the wealth of knowledge of cotton genetics because of its importance as a crop plant. To facilitate the transfer of such knowledge from well-known groups like Gossypium to less well characterized wild species groups (such as Hibiscus section Furcaria) the current project will use an understanding of the alcohol dehydrogenase gene family developed in Gossypium to address species relationships Hibiscus section Furcaria. Thus, this project provides a direct test of the transferability of information gleaned from a genetically well characterized group (Gossypium) to a less well understood group (Hibiscus section Furcaria).