The Phylogenetic Relationships of Tortula: An SEM Survey and a Preliminary Cladistic Analysis

This paper focuses on three phylogenetic questions involving the large and diverse moss genus Tortula: (1) a search for characters justifying a monophyletic group within the tribe Pottieae to which the name Tortula can be applied; (2) an evaluation of evidence for the monophyly and proper circumscription of the T. ruralis complex; and (3) an examination of the phylogenetic interrelationships of selected additional species of Tortula. An extensive SEM survey was undertaken, emphasizing taxa relevant to these three questions. Fifty-five populations of 31 species of Tortula, as well as 21 species in 13 other genera, were studied for peristomes and spores; in addition, leaf characters of 20 populations of 18 species of Tortula and other genera were studied. Results of this SEM survey indicated that spore and leaf ornamen- tation was not in general useful for higher-level groupings. Peristome characters, especially orna- mentation, were useful. These and other characters from light microscopic observations were ana- lyzed cladistically. It is concluded that Tortula as currently circumscribed is paraphyletic. However, a smaller monophyletic group (Tortula sensu stricto) can be recognized, of which the T. ruralis complex (including T. caninervis) appears to be a monophyletic subgroup. The circumscription of Tortula Hedw. has long been disputed. Hedwig (1782, 1801) characterized Tortula as monoecious, with male flowers gem- miferous, while Barbula was dioecious, with male flowers capituliform. In the early literature the use of these two generic names is inconsistent. As Steere (1940) described the situation, .. . the two generic names were for a long time used more or less interchangeably and even indiscriminately. Hooker and Greville (1824) and De Notaris (1838, 1862) followed a broad generic concept and includ- ed in Tortula all species with spirally twisted peri- stome teeth; these species belong to several modern genera. Other early workers placed these same species