Delivered by Publishing Technology to: Germinal Rouhan IP: 192.134.152.181 on: Thu, 10 May 2012 12:42:51 Copyright (c) American Society for Plant Taxonomists. All rights reserved. Systematic Botany (2012), 37(2): pp. 331–338 © Copyright 2012 by the American Society of Plant Taxonomists DOI 10.1600/036364412X635386 Not so Neotropical After all: the Grammitid Fern Genus Leucotrichum (Polypodiaceae) is also Paleotropical, as Revealed by a New Species from Madagascar Germinal Rouhan, 1,4 Paulo H. Labiak, 2 Emile Randrianjohany, 3 and France Rakotondrainibe 1 1 Muse ´um national d’Histoire naturelle, UMR CNRS 7205 ’Origine, Structure et Evolution de la Biodiversite ´’, Herbier national, 16 rue Buffon CP39, F-75005 Paris, France. 2 Universidade Federal do Parana ´, Departamento de Bota ˆnica. Caixa Postal 19031. CEP 81531-980, Curitiba-PR, Brazil. 3 Centre National de Recherches sur l’Environnement, Laboratoire de Microbiologie de l’Environnement, Antananarivo, Madagascar. 4 Author for correspondence: rouhan@mnhn.fr Communicating Editor: Andrew Hipp Abstract—Based on morphological and molecular evidence (DNA sequences from six plastid regions: atpb, rbcL, trnG-trnR, trnL-trnF, atpb-rbcL, and rps4-trnS), the new fern species Leucotrichum madagascariense is described from Madagascar, where it is found in the North (Marojejy), Centre (Andringitra), and South (Andohahela) regions. Leucotrichum madagascariense has long, whitish laminar hairs, among the other distinguishing characters of the genus: arching fronds, laminar apices subconform to the lateral pinnae, dark sclerenchyma covered by the green laminar tissue, and laterally marginate petioles. Its most remarkable feature is the lack of rhizome scales, a character that is shared with the Neotropical L. pseudomitchelliae. However, our phylogenetic results suggest that this character has evolved twice independently within the genus. In contrast, the sister relationship between the new Madagascan species and the group composed of L. schenckii and L. mortonii is morphologically supported by linear and deeply pinnatifid laminae, incised 2/3–3/4 of the way to the rachis along its length. Leucotrichum madagascariense is the only representative of the genus known from the Old World. Because it is nested within a clade of five Neotropical species, we hypothesize that its occurrence outside the Neotropics results from one long-distance dispersal event from America, likely southeastern Brazil, to Madagascar. Keywords—cpDNA, Grammitidaceae, Indian Ocean, long-distance dispersal, phylogeny, pteridophytes. Madagascar is a hotspot of plant diversity (Myers et al. 2000), especially for ferns: among the more than 12,000 spe- cies of vascular plants listed on the island (Catalogue of the vascular plants of Madagascar 2011), ca. 600 species are ferns, 45% of which are endemic (Rakotondrainibe 2003a, b). Due to extensive human activities and habitat destruction, most of the fern diversity is nowadays restricted to remains of primary evergreen rainforests, mainly in the remote mountains of the eastern part of the island. The grammitid ferns (Polypodiaceae) represent a diversified fern group in Madagascar (ca. 40 species; Rakotondrainibe et al. in prep.) with 55% endemics. Grammitid ferns are defined as a strongly supported mono- phyletic group nested within Polypodiaceae (Ranker et al. 2004; Schneider et al. 2004a). Therefore, grammitids are usually not recognized as the family Grammitidaceae anymore, to avoid rendering the Polypodiaceae paraphyletic (Ranker et al. 2004; Schneider et al. 2004a). Grammitids grow mostly as epiphytes at high elevations in tropical mountainous humid forests (Parris 2009). They are easily distinguished from other Polypodiaceae by green (chlorophyllous) and trilete spores (vs. yellow and monolete; Mettenius 1846; Ching 1940), one- cell-wide sporangial stalks (vs. more than three cells wide; Wilson 1959) and fronds without scales but generally with uniseriate and pluricellular setae (Ching 1940; Holttum 1947). The grammitids include more than 29 genera and 750 spe- cies worldwide. They are most diversified in the Old World, with likely more than 500 species (Parris 2009), and espe- cially in Asia. However, many recent phylogenetic studies focused on mostly Neotropical taxa have resulted in the recognition of several new monophyletic genera such as Leucotrichum Labiak (Labiak et al. 2010a), Alansmia M. Kessler, Moguel, Sundue & Labiak (Kessler et al. 2011), Ascogrammitis Sundue (Sundue 2010; Sundue et al. 2010), Moranopteris R. Y. Hirai & J. Prado (Hirai et al. 2011), Stenogrammitis Labiak (Labiak et al. 2010a, b), and Galactodenia (Sundue et al. 2012). Leucotrichum was segregated from Lellingeria A. R. Sm. & R. C. Moran (Labiak et al. 2010a) and was described as com- prising five species, two occurring in southeastern Brazil (L. organense (Gardner) Labiak and L. schenckii (Hieron.) Labiak), two in Central-America (L. mitchelliae (Baker ex Hemsl.) Labiak and L. pseudomitchelliae (Lellinger) Labiak), and two in the Antilles (L. mitchelliae and L. mortonii (Copel.) Labiak). Leucotrichum is morphologically characterized by arching fronds, clathrate rhizome scales with blackish cell walls, laterally marginate petioles, laminar apices subcon- form to the lateral pinnae, segment costae without blackish sclerenchyma, and whitish setae bearing acicular branch cells (Labiak et al. 2010a). In the course of revising the systematics of grammitid ferns for the western Indian Ocean area, we found speci- mens from Madagascar exhibiting characters that did not match with the morphology of any of the genera known in the area or elsewhere in the Paleotropics. Instead, the Madagascan specimens exhibited striking characters of the Neotropical Leucotrichum, in particular the whitish laminar setae. Therefore, we corroborated our hypothesis through phylogenetic analyses using molecular data, which are based on an extensive taxonomic sampling. Based on the results, we here describe the Madagascan collections as a new species of Leucotrichum. Phylogenetic results also shed light on the evolutionary relationships of this new species to other grammitid ferns. Materials and Methods Morphology and Taxonomy—Herbarium specimens were observed under a stereomicroscope, and the following characters were used to compare the unidentified Madagascan specimens with other grammitids, especially the five known species of Leucotrichum: scales of the rhizome, shapes and measures of laminae and segments, and induments on petioles and laminae. Personal field observations were used to charac- terize the habit and position of the fronds relative to the rhizomes. As 331