A New Species of Dicranodontium (Musci: Dicranaceae) from Panama

Abstract

The presence of an autoicous species in Dicranodontium (Dicranodontium intermedium, species nova) further supports Williams's taxonomic decision to unite Atractylocarpus and Dicranodontium. Dicranodontium is a group of medium-sized mosses typically having narrow to setaceous leaves, broad costae, linear leaf cells, nonsheathing perichaetial leaves, and cygneous setae. The genus is gametophytically identical to Atractylocarpus: the genera differ only in sexuality (dioicous in Dicranodontium, autoicous in Atractylocarpus) and the stance of their moist setae (cygneous in Dicranodontium, erect to flexuous in Atractylocarpus). Based on his observations on the variability of setae curvature within identical species, Williams (1913) synonymized the two genera. The following new species of Dicranodontium, which has a cygneous seta but is autoicous, adds further support to William's taxonomic view of these two genera. Dicranodontium intermedium Allen, sp. nov. TYPE: Panama. Chiriqui: Volcain Baru, 8?45'N, 82?30'W, Allen 9123 (holotype, MO; isotypes, NY, PMA). Figures 1-7. Species nova D. meridionali affinis, a qua differt facie grossiore, sexuali statu autoico et cellulis interioribus basalibus foliorum incrassatis, porosis. Plants medium sized, in loose, erect, greenish yellow tufts, epiphytic or occasionally terrestrial. Stems moderately to densely white or red-tomentose, up to 5 cm long, branching irregularly; epidermal cells thick-walled, red-brown. Leaves evenly and well spaced, erect-spreading to falcate; concave below, tubulose above, narrowly lanceolate from a shortly ovate base, 8-11 mm long, apex long setaceous, sharply and densely denticulate above. Upper leaf cells linear, firm-walled; median leaf cells long-rectangular, incrassate and porose, occasionally smoothwalled; basal cells near the costa rectangular, incrassate and strongly porose, the outer basal cells longer and narrower forming a short, hyaline border; alar cells well developed, red-brown, occasionally fugacious. Autoicous. Perigonia terminal on short branches (1.5-5.0 mm) below the perichaetia. Setae yellow becoming red, smooth, 10-13 mm long, red, twisted and erect when dry, cygneous when wet. Capsules erect and symmetrical, smooth or weakly furrowed when dry, oblong, 2.0-2.5 mm long, lightly roughened at base; peristome yellowish becoming dark red; teeth 0.5 mm long, deeply divided (at times almost to the base), dorsal surface vertically striate. Opercula 1.5 mm long. Calyptrae 3.0 mm long, entire at base. Spores lightly papillose, yellow, 20 ,im. Paratypes. PANAMA. CHIRIQUI: Volcan Barf, Allen 9127, 9132, Davidse & D'Arcy 102901 (all MO). Epiphytic on branches in subcanopy, on tree trunks, fallen logs and occasionally terrestrial between 2,300 and 3,505 m. Dicranodontium intermedium has broad leaves that are atypical for the genus. In gross aspect it looks very much like a species of Campylopus. Furthermore, its well-developed alar cells and incrassate, porose basal leaf cells are common features of that genus. However, its linear upper leaf cells and autoicous sexual condition cannot be accommodated in Campylopus. Three species of Dicranodontium (sensu Williams, 1913) are now known from Central America. They are separated in the following key.