| Summary: | The Bryaceae are one of the largest families of mosses and are of particular interest because of a relatively primitive position in relation to other families. Although a number of recent taxonomic studies have been devoted to genera of the subfamily Bryoideae, few have considered taxa in other subfamilies. Pohlia is the largest genus in the Pohlioideae and accounts for about 80% of the species found in the subfamily. As progress toward a phylogenetic analysis of the Bryaceae, Pohlia is the focus of this morphological and ecological study. The morphological relationships between species and supraspecific taxa are analyzed using two cladistic methods (character compatibility analysis and the Wagner Tree method) and several phenetic approaches including those based on information theory. About 500 substrate samples were gathered representing 24 North and Central American Pohlias, and pH, organic matter content, and concentrations of exchangeable calcium and magnesium were measured. A revision of the North and Central American species includes descriptions, illustrations, and distribution maps, and a key to thirty-six species and two varieties. Cladistic and phenetic analyses support the recognition of four major groups of species of Pohlia. Species of sections Mniobryum and Cacodon (classified in subgenus Mniobryum) occur most frequently on mildly acidic to strongly basic soils of low organic content. Species of subgenera Nyholmiella (subg. nov.) and Pohlia are most frequent on strongly to mildly acid soils of a more organic nature. Nyholmiella taxa are almost all tropical in distribution, (subg.) Pohlia is represented worldwide, and Cacodon (including section Mniobryum) is most diversified in temperate to subarctic regions. Morphological and ecological data indicate that primitive species of the genus were presumably of moderate size, with long, narrow leaf cells, and perfect peristome structure, and occurred on mildly acidic soils of relatively high organic matter content. PhD Botany University of Michigan ...
|
|---|