Tortella fragilis (Pottiaceae) Reported for Southern South America

Abstract

Tortella fragilis is reported for the first time for South America. Tortellafragilis (Hook. & Wils.) Limpr. has been considered as a species confined exclusively to the northern hemisphere (Saito 1975; Steere 1978). Recent collections from New Zealand (Fife 1984; Vitt 1974) and South Africa (Magill 1981), as well as a revision of the collections reported by Greene et al. (1970) from the Antarctic (orginally described as Sarconeurum tortelloides S. W. Greene), however, have revealed that the species actually has a bipolar range with a disjunct occurrence in Hawaii (Zander & Hoe 1979). It is thus not surprising that the species was found also in southern South America (see below). Similarly, Greene (1975) reported the occurrence of S. glaciale (C. Miill.) Card., a species with a much wider distribution in the Antarctic than T. fragilis, in southern South America and some subantarctic islands. The latter species has been found in the Andes of South America and probably the same is also true for T. fragilis, although this has not yet been documented. The specimens found in Tierra del Fuego were collected on bare soil and schistose gravel from sea level to 610 m. Similar habitats are readily available also in more northern parts of the mountains. In all Fuegian localities the species was fairly sparse. Tortella tortuosa (Hedw.) Limpr. has been collected in more northern parts of South America (Churchill 1989; Matteri 1985; Seki 1974). Zander and Hoe (1979) present a small scale culture study of the Hawaiian material of T.fragilis (distinguished as var. tortelloides (S. W. Greene) Zander & Hoe) and discuss the possibility that T. tortuosa and T. fragilis var. tortelloides are possibly only partially differentiated genetically. This view is further discussed by Eckel (1991), who recognizes the variety as a distinct species as originally presented by Robinson (1972). This is due to the extensive studies by Zander of the Arctic material showing that T. fragilis and T. tortelloides do not intergrade. Eckel (1991) discusses the possibility that var. tortelloides originated as an ecological modification of T. tortuosa. The plants collected in Tierra del Fuego, however, show intermediate characters between T. fragilis and T. tortelloides as given by Zander and Hoe (1979). Stems are up to 25 mm high, leaves with less propaguloid apices are over 4 mm long, apical margins of leaves are essentially straight, laminal cells generally have a diameter of 9-11 Am, marginal cells are differentiated, reaching ca. 1/2-/ of the total le f length or they are weakly differentiated in small patches, and adaxial quadrate cells cover ca. 1/2-/4 of the distal part of the costa either totally or partially, being confined to the region adjacent to the costa except at the extreme apex. The specimens reported from New Zealand were assigned to the northern T. fragilis var. fragilis by Fife (1984). Accordingly, the Fuegian specimens are also tentatively assigned to T. fragilis. However, the identity of the southern hemisphere specimens remains doubtful until a thorough study of the whole genus