The genera Chionoloma, Oxystegus, Pachyneuropsis and Pseudosymblepharis (Pottiaceae, Bryophyta)taxonomy and phylogeneticrelationships

Abstract

Pottiaceae is the largest known moss family, with one of the most complex taxonomies among the bryophytes. The circumscription of genera within the Pottiaceae is challenging and it has been a matter of dispute ever since the establishment of the family. In this thesis, four related genera belonging to the Pottiaceae subfamily Trichostomoideae are studied: Chionoloma Dixon, Oxystegus (Limpr.) Hilp., Pachyneuropsis H.A. Mill. and Pseudosymblepharis Broth. The main goals of this work are (i) to resolve phylogenetic relationships among these four related traditional genera of the Pottiaceae inferring a phylogeny derived from nuclear and the plastid markers; (ii) to provide a comprehensive taxonomic synthesis of the species placed within Chionoloma, Oxystegus, Pachyneuropsis and Pseudosymblepharis worldwide and (iii) to search for new molecular markers of potential phylogenetic utility by assembling the chloroplast and mitochondrial genome of two species of these genera, Oxystegus tenuirostris var. tenuirostris (Hook. & Taylor) A.J.E. Sm. y Pseudosymblepharis schlimii M. Alonso, M.J. Cano & J.A. Jiménez. In order to achieve the first goal, a phylogeny derived from nuclear ITS and the plastid markers atpB-rbcL, trnG and trnL-F is inferred. Putative monophyly of these four genera is investigated using maximum likelihood and Bayesian inference analyses. Ancestral state reconstruction shows high levels of homoplasy in the characters historically used for the generic division of Chionoloma s.l. Based on the results, it is suggested that Chionoloma, Oxystegus and Pseudosymblepharis should be merged into a single genus, for which the oldest name Chionoloma has priority. Additional analyses are needed to clarify the taxonomic status of Pachyneuropsis. The taxonomic revision is based on more than 2,600 specimens deposited in different herbaria or collected during filed trips. A total of 131 names are found and their nomenclatural types are examined, carrying out the lectotypification of 69 names. As a result of this revision, keys, descriptions, illustrations, photographs and distribution data of each species are provided. After the taxonomic study, it is concluded that Chionoloma is composed of 22 species and one variety, 18 of them are here newly combined and a new species is described and illustrated. Moreover, 56 names are newly synonymized and a total of 87 new records for various countries are reported. On its behalf, results related with Pachyneuropsis show that this genus includes two species, being one of them a new combination. Besides, two names are considered as new synonyms. The search for new molecular markers is based on genomic studies focus on complete the organellar genome of two species of this group. Just the mitochondrial genome of the species Chionoloma tenuirostre var. tenuirostre is assembled and annotated. The genome is 105,001 bp long, with a GC content of 39.2%, comprising 40 protein coding, 24 tRNA, and 3 rRNA genes. All introns reported from the mitochondrial genome of all but one peristomate moss are present, whereas no 50 bp region is repeated within the genome. The genic content and order is identical to that of most mosses, highlighting that the mitochondrial genome is static not only across the phylogenetic depth but also breadth of the moss tree of life. A phylogenetic tree is inferred from the whole genome of 16 species of mosses to validate the sequence of C. tenuirostre var. tenuirostre by confirming its shared ancestry with Syntrichia Brid. Broadly, this thesis constitutes not only the first phylogenetic study of the genera Chionoloma, Oxystegus, Pachyneuropsis and Pseudosymblepharis but also the first taxonomic revision of this group and one of the few genomic studies with bryophytes performed so far.