Actinodontium ascendens Schwagr.

Actinodontium ascendens Schwägr.

SPECIMEN EXAMINED. — Madagascar. Toamasina: Valley of Marimbona R., W of Soanierano, Antasibe; 350 m; 16°53’59”S, 49°34’59”E; 13.XII.1938; Lam & Meeuse 5948C (L[L0836988]!, MO[MO-6234681]!).

NOTES

The genus Actinodontium Schwägr. is newly reported for Madagascar based on a specimen in L with a duplicate in MO that was originally annotated as “ Lepidopilum sp. nov. ”. Actinodontium is similar to some Lepidopilum (Brid.) Brid. species, particularly those in the L. longifolium group (Churchill 1988), in having erect, evenly foliate stems; symmetric, elimbate leaves with prominent double costae; and a daltoniaceous-type peristome consisting of pale, narrowly triangular exostome teeth that are papillose on both surfaces and lack median furrows, as well as papillose endostome segments above a low or high basal membrane. The genera differ in that Actinodontium has mostly smooth setae and glabrous calyptrae, compared to the more consistently papillose to spinose setae and pilose calyptrae of Lepidopilum. There are presently five accepted species in Actinodontium: the southeastern Asian and Oceanic A. ascendens and A. rhaphidostegum (Müll.Hal) Bosch & Sande Lac., the West African A. streptopogoneum Broth., and the Caribbean and Central American A. pygmaeum W.R.Buck and A. sprucei (Mitt.) A.Jaeger (Mohamed & Robinson 1991; Müller & Pócs 2007; Allen 2010). Actinodontium ascendens and A. rhaphidostegum were regarded by Tan & Robinson (1990) as potentially identical, while Allen (2010) noted strong affinities between A. ascendens, A. rhaphidostegum and A. sprucei. A mixture of features from these three species are observed in the Madagascar specimen, lending additional support that they may be conspecific. The Madagascar specimen, like A. ascendens, A. rhaphidostegum and A. sprucei, has sparsely branched, 1.2-1.5 cm tall plants that are denselyleaved and with a golden color. Furthermore, the size of the lateral leaves, 2.4-3.0 × 0.7-0.9 mm, and the oblong-lanceolate shape, overlaps with that of all three species, although the leaf dimensions are somewhat shorter and narrower than typical A. rhaphidostegum specimens. Also, the variable lateral leaf apices of the Madagascar specimen tend to be gradually acute to short-acuminate and are more consistently similar to A. ascendens and A. sprucei rather than A. rhaphidostegum, which often has longer apices, but sometimes can have shortacuminate apices as well. Additionally, the leaf margins of the Madagascar specimen are narrowly revolute and mostly entire or slightly serrulate near the apices, features shared by all three Actinodontium species, along with their hexagonal to elongate-rhomboidal leaf cells and double costae that extend approximately ½-⅔rds the leaf length, and do not protrude. While the erect, cylindrical capsules, 2.3-2.8 mm long (including the operculum), of the Madagascar specimen overlap in size with all three Actinodontium species, this range is at or slightly exceeds the upper range for capsule length in typical A. ascendens specimens. The Madagascar specimen lastly has clusters of uniseriate, 5-7-celled gemmae in the leaf axils, identical to those described for A. sprucei. While gemmae have not apparently been described previously for A. ascendens and A. rhaphidostegum, similar gemmae were found in a specimen of A. rhaphidostegum from Fiji (Hegewald & Hegewald 11785, MO). The name A. ascendens is assigned to the Malagasy specimen given the strong phytogeographic affinities between the Madagascar and southeast Asian floras.

Actinodontium ascendens also has priority as the oldest name among the three species, if A. rhaphidostegum and A. sprucei should indeed later prove to be conspecific with it.