Phylogenetic relationships and morphological character analysis of Thelia Sull. (Bryophyta)

Recent technical advances allowing for the rapid acquisition of molecular (DNA sequence) data have made it possible to address long-standing questions regarding bryophyte phylogeny. These data have been used to clarify relationships and (re)define taxonomic groupings at the generic level and above. Two families that have been poorly delimited on the basis of morphology are Thuidiaceae and Leskeaceae. Additionally, the phylogenetic position of the small but distinctive genus Thelia remained unclear. To clarify limits for these two families as well as determine the monophyly and sister-group relationships of Thelia, cladistic analyses were performed using both morphological and molecular data.; A second, more detailed analysis of thirty stem and branch leaf characters in Thelia was conducted. Attempts were made to evaluate these characters with regard to the following criteria: homology, heritability, independence, and discrete states. Initial assessments of homology were based largely on similarity in structure, position, and developmental stage. A preliminary culture study was performed to determine how clonally-propagated gametophores representing six different genotypes (two per taxon) would respond to three environmental treatments (nutrient level, moisture level, and light intensity) when grown under identical conditions. Results showed significant levels of variation among genotypes and between treatments with regard to the total (dry) weight and number of branches in each specimen. Character independence was evaluated by calculating Spearman rank correlation coefficients and subjecting these values to tests of significance. This was supplemented by multivariate R-mode (variable) and Q-mode (sample) principal components and factor analyses. Results indicated significant correlations among a majority of variables, rendering them inappropriate for use in a cladistic analysis based on the independence criterion. Attempts were made to discretize characters parametrically through single-factor analysis of variance and multiple comparison tests. While all ANOVAs were highly significant, several different multiple comparison tests failed to define any usable states for a cladistic analysis within Thelia.; In order to clarify relationships within Thelia, DNA sequence data (Adk and rps4) from specimens collected across the ranges of all three species were analyzed cladistically. Results for both rps4 and Adk supported morphologically-based distinctions for all three species. Although rps4 sequence data could not resolve relationships among the three taxa, Adk sequence data indicated that T. hirtella and T. lescurii are sister to one another, both being derived from an T. asprella-like ancestor. Additionally, scanning electron microscopy revealed subtle micromorphological differences in peristome ornamentation patterns among the three species. (Abstract shortened by UMI.)...