| With over 500 species, the Orthotrichaceae (Bryopsida) are one of the largest families of mosses. Twenty-five genera are currently included in the Orthotrichaceae, with Macromitrium and Orthotrichum accounting for most of the taxonomic diversity. Together with the Erpodiaceae, Rhachitheciaceae, Microtheciellaceae and the Helicophyllaceae, they form the Orthotrichales. The limits and the relationships of the family and the order are here examined. The Microtheciellaceae are now excluded from the Orthotrichales on the basis of their pleurocarpy. The Helicophyllaceae are characterized by a unique combination of gametophytic characters, and are tentatively excluded, although with no clear affinities to other groups. Comparisons of nucleotide sequences of the chloroplast gene rbcL suggest that the Rhachitheciaceae and the Erpodiaceae belong to the Haplolepideae, and should therefore be excluded from the Orthotrichales. The genera Kleioweisiopsis, and Trigonodictyon, as well as Octogonella and Uleastrum are excluded from the Orthotrichaceae based on comparison of morphological characters, and transferred to the Ditrichaceae, Grimmiaceae, and Rhachitheciaceae, respectively. Pleurozygodontopsis is placed in synonymy with Zygodon. Cladistic analysis of 37 rbcL nucleotide sequences furthermore lead to the exclusion from the Orthotrichaceae of two gymnostomous genera, namely Amphidium, and Drummondia, both with affinities to the Haplolepideae. Twenty-two genera, including two new genera, Bryomaltaea and Matteria, as well as the reinstated genus Codonoblepharon, are now accepted within the Orthotrichaceae. These genera are distributed between four tribes belonging to two subfamilies. The sister-group to the Orthotrichales, now reduced to the Orthotrichaceae, remains somewhat ambiguous but is hypothesized, based on morphological characters to be the Bryales, rather than the Splachnales. |
