A new species of Asplenium section Thamnopteris ( Aspleniaceae ) from Indonesia

A new species, Asplenium riswanii (sect. Thamnopteris), is described from Central Java and West Papua, Indonesia. It is distinct from any known species by having thick and rigid fronds, abaxially keeled midribs, broadly lanceolate scales, and distantly spaced sori. Morphologically, A. riswanii is not similar to any species from Malesia but somewhat close to A. antrophyoides from mainland Southeast Asia. Molecular data reveal it has an isolated position in the phylogeny. The micromorphology of spores and leaf epidermis of A. riswanii is also documented and a key to the species of Asplenium sect. Thamnopteris from Malesia is given.

When attempting to update the taxonomy of Asplenium sect.Thamnopteris, we found a cultivated plant with peculiar morphology in Bogor Botanical Garden, West Java, which was readily recognized as belonging to Thamnopteris but could not be identified as one of the known species.An earlier collection from Nusakambangan, Central Java was subsequently found with similar morphological features to the living plant in Bogor.Further observations on the morphology of spores and leaf epidermis confirmed that the two plants were conspecific and they represented a new species.The new species is now described as A. riswanii S.Y.Dong.

MATERIAL And METHodS
Only two specimens of the new species are hitherto known.The leaf epidermis of the two specimens, as well as some related species, was anatomically examined using the method described in Wang & Lu (2010).The spore samples of both specimens and related species were observed in a scanning electron microscope (SEM) following the method in Dong & Zhang (2005).The measurements of spore size or stoma size are the average of 20 spores or 20 stomata, respectively.The recognition of seven species in Malesia and the diagnostic characteristics used in the key are based on the morphological examination of c. 2 500 specimens in the following herbaria: BM, BO, GAUA, IBK, IBSC, K, KUN, KYO, L, P, PE, PNH, PYU, SING.
For the extraction and amplification of DNA and the subsequent analysis, we refer to Wei et al. (in prep.).dESCRIpTIon Asplenium riswanii S.Y.Dong,2a,b,d,    West Papua in 2007.The two specimens are in agreement with each other in many key characters of macromorphology: broadly lanceolate scales; the size, shape, and particular thick texture of fronds; abaxially keeled midribs; and the distribution, length, and the distantly spaced sori.Likewise they are similar in the micromorphology of leaf epidermis and spores: the shape and size of epidermal cells on either surface, the pattern and size of stomata, the lophate perispores, and the alate folds and echinulate ornamentation on perispores (Fig. 2).Clearly the two specimens represent a single species.
Being characterized by broad scales, keeled midribs, distantly spaced sori, and extraordinary thick texture of fronds, A. riswanii is not morphologically similar to any known sympatric species but somewhat similar to A. antrophyoides H.Christ from mainland Southeast Asia (southwestern China, northern Vietnam, and northern Thailand).The two species are similar in frond size and features of stipe scales and midribs, but A. riswanii differs from A. antrophyoides in fronds being much thicker and more rigid in texture, gradually tapering toward the base from the middle (vs more or less abruptly narrowed at upper part of fronds in A. antrophyoides), and much more distantly spaced sori (4 -5 vs 7-12 sori every 2 cm along midribs).In micromorphology of both leaf epidermis and spore ornamentation, there are also some differences between A. riswanii and A. antrophyoides.The ornamentation of the perispore, which was recently demonstrated to be taxonomically significant between species in Asplenium sect.Thamnopteris (Wei & Dong 2012), shows lower folds in A. riswanii (c. 2 μm) than in A. antrophyoides (c. 5 μm).The stomata of A. riswanii are of the anisocytic, diacytic, or tetracytic type, and the outline of the stomata is nearly circular (with the length/width ratio being 1.2-1.3);while the stomata in A. antrophyoides are usually of the diacytic or polocytic type and are elliptic in shape (length/ width ratio 1.5-1.7)(Fig. 2).
Besides the morphological comparison, we also conducted phylogenetic analyses of A. riswanii and other species of the section Thamnopteris based on two datasets of plastid sequences (separate rbcL and a combination of psbA-trnL, rbcL, and trnL-F).The plastid sequences, either the rbcL or the combination of the three, indicate that A. riswanii is not clearly close to any known species.In a phylogenetic tree based on rbcL sequences of 37 accessions (including one each of two outgroups) (Fig. 3), A. riswanii is resolved as clearly separate from a number of well-supported clades.A comprehensive discussion of the phylogeny of this group will be presented in a separate paper (Wei et al, in prep.).

A new species of Asplenium section Thamnopteris (Aspleniaceae) from Indonesia S
.Y. Dong 1 , Mujahidin 2 , L.L.Wei 1,3, Y.S. Chao4Asplenium riswanii (sect.Thamnopteris), is described from Central Java and West Papua, Indonesia.It is distinct from any known species by having thick and rigid fronds, abaxially keeled midribs, broadly lanceolate scales, and distantly spaced sori.Morphologically, A. riswanii is not similar to any species from Malesia but somewhat close to A. antrophyoides from mainland Southeast Asia.Molecular data reveal it has an isolated position in the phylogeny.The micromorphology of spores and leaf epidermis of A. riswanii is also documented and a key to the species of Asplenium sect.Thamnopteris from Malesia is given.
2Center for Plant Conservation, Bogor Botanical Garden, Indonesia Institute of Sciences, Bogor 16003, Indonesia.3GraduateUniversity of the Chinese Academy of Sciences, Beijing 100093, China.4Division of Botanical Garden, Taiwan Forestry Research Institute, Taipei 10066, Taiwan.