| The primary objective of the present study was to characterize the phylogenetics and evolution of the poorly studied moss Mitthyridium (Calymperaceae: Musci). The research consisted of 3 primary components. The first was a methodological analysis in which the utility of a nuclear gene, glyceraldehyde 3-phosphate dehydrogenase (gpd), for phylogenetic studies of mosses was assessed. This study illustrated that the low copy gene gpd evolves at a rate as much as 3 times that of two amplicons commonly used for phylogeny reconstruction (the chloroplast (cpDNA) genes rps4 and trnL) Phylogenetic analyses of 26 ingroup and 20 outgroup taxa using the full gpd amplicon yielded well resolved trees that were in general accord with the trees derived from the cpDNA partitions. This study also solidly confirmed the monophyly of Mitthyridium and identified its closest outgroups as members of a paraphyletic “syrrohopodon.”; In the second component of this research, a hypothesis of evolutionary rate constancy in the exons of gpd could not be rejected using a phylogeny of 80 lineages in Mitthyridium. The average maximum age of the most recent common ancestor to Mitthyridium was estimated to be 8.1 ± 1.3 million years old. Having determined this date, a statistical estimator was used to determine that the rate of diversification of this young group and its internal nodes was 0.56 ± 0.004 new lineages per million year.; Finally in the third component of this dissertation the high diversity of Mitthyridium is described in a phylogenetic monograph that treats 112 ingroup and 4 outgroup taxa. Simultaneous analysis of DNA sequences from gpd, rps4 and trnL, as well as a morphological character partition reconstructed well-supported trees to serve as the backbone for the phylogenetic taxonomy that was based on two criteria: (1) monophyly and (2) ease of diagnosability. Phylogenetic analyses demonstrated unequivocally the existence of at least 13 distinct clades: crassum, constrictum, undulatum luteum, perundulatum, subluteum, jungquilianum, fasciculatum, repens, obtusifolium, microundulatum, papuanum , and leucoloma. Virtually all of these named clades consisted of numerous uniquely evolving lineages—totaling 67—that failed to meet the second criterion. (Abstract shortened by UMI.)... |
