UC Berkeley

Scleropodium is a genus of six species in the Brachytheciaceae. Although they are common in north temperate zones, they have not received monographic treatment in over a century. The aims of this study were to test species circumscriptions within the genus with molecular data, complete a thorough global taxonomic treatment of the genus, and to quantitatively investigate the ecological preferences of the species.

A molecular phylogenetic study was conducted using 104 individuals spanning the range of morphological variation and the geographic extent of the genus. Maximum Parsimony and Bayesian phylogenetic analyses and a statistical parsimony network analysis of ITS and the chloroplast rps4, bsbA2 and trnG regions were performed. Although slight differences were found among analyses, there were six clear molecular groups. Five of these corresponded directly to the species Scleropodium californicum, S. cespitans, S. julaceum, S. obtusifolium and S. touretii. The sixth species, S. occidentale, is new to science and is described here. It is similar in ecology and morphology to S. obtusifolium, but has several diagnostic features in both molecular markers and morphological characters. Molecular data also revealed that S. australe, previously recognized as an endemic species in Tasmania, is nested in phylogenetic analyses within European S. touretii.

For the taxonomic treatment, specimens from across the global distribution of the genus were obtained and examined. Earlier taxonomic problems are resolved and new determinations of many herbarium specimens resulted in substantial changes in the known geographic distributions of the species. Nomenclatural problems are addressed, including lectotypification of S. cespitans, neotypification of S. touretii, and snynonymization of S. colpophyllum with S. cespitans and S. australe with S. touretii. Two Korean species, S. brachyphyllum and S. coreense, are excluded from Scleropodium.

A study of niche differences among five of the six species was conducted in the coast ranges of California. The study employed twenty-eight100m2 plots to investigate mesosite and microsite differences among species. Differences could be found in all species pairs except for S. obtusifolium and S. occidentale, both of which are restricted to seasonal drainages. Environmental factors that were important at broad spatial scales included slope and tree canopy cover. Finer scale differences at the scale of individual moss patches were found in distance of the moss patches from drainages, substrate type and shade. Although niche differences were observed and quantified, niche overlap was extensive and mixed moss patches with two species growing intertwined were common. Niche differences among sexes within species was also investigated, but results were mostly not significant. In the more common species, there were trends toward female sex ratio bias and restriction of male individuals to more mesic habitats, but these results were mostly confounded by numbers non-expressing individuals.