Begonia yapenensis (sect. Symbegonia, Begoniaceae), a new species from Papua, Indonesia

A new species, Begonia yapenensis M.Hughes, in Begonia section Symbegonia (Begoniaceae) is described and diagnosed against Begonia sympapuana. The new species is endemic to Yapen Island, Papua, Indonesia, and is currently known from a single collection.


Introduction
Begonia section Symbegonia (Warburg 1894: 149;Forrest & Hollingsworth 2003: 208) is endemic to the island of New Guinea and comprises 13 species (Sands 2009). The section was recognised at the genus level prior to a molecular phylogenetic study (Forrest & Hollingsworth 2003) which found it to be nested within Begonia section Petermannia (Klotzsch 1854: 124;de Candolle 1859: 128). The section is well defi ned morphologically by species having the tepals of the female fl owers fused into a tubular corolla, the tepals of the male fl owers often fused and usually with columnar androecia and unique endothecial cells in the anthers (Tebbitt & MacIver 1999). However many of the species within the section are diffi cult to delimit. It is tempting to speculate that the large amount of highly dissected yet fairly continuous montane habitat on New Guinea has promoted rapid yet incomplete diversifi cation in this group, leading to diffi cult species complexes. The tubular fl owers are very different from those in other sections of the genus, and hence the pollination syndrome is likely to differ also. Increased population connectivity, possibly mediated by bird pollination, may also contribute to the persistence of widespread species complexes, which would otherwise fragment into different taxa in the absence of gene fl ow (Hughes & Hollingsworth 2008). In addition to this biological complexity, the diversity in Begonia sect. Symbegonia is further diffi cult to interpret as the species have been described separately over the decades, most without reference to existing taxa and hence without comparative diagnoses. During preparation for a taxonomic revision of the section by two of the authors, it became clear that a recent collection from Yapen Island, Papua Province, Indonesia represents a new species which is described below.

Materials and methods
All available specimens of Begonia sect. Symbegonia in B, BM, BO, E, FI, K, L, P and SING were examined (272 sheets representing 171 collections), including the types for all names in the section in order to confi rm the novelty of the collection from Yapen Island. The description was based on living material in cultivation at the Royal Botanic Garden Edinburgh and later pressed as the holotype. The terminology in the description follows Beentje (2010).

Distribution
Indonesia. Only known from the type locality in central Yapen Island, Papua Province (Fig. 2).  (Merrill & Perry 1943: 59;Forrest & Hollingsworth 2003: 208), which shares the rugose leaves with reddish veins and broadly similar infl orescences and fl owers. Begonia yapenensis sp. nov. differs in being a smaller, lower growing plant with shorter internodes and a white undumentum (not reddish), the leaves having shorter petioles (ca. 5 mm, not 1-1.5 cm), male fl owers with tepals fused halfway (not shortly fused at the base) and fewer stamens (6-9, not ca. 15) which are arranged along a short column (not arising from a short torus), and fruits which have more attenuate wings. Plants of B. yapenensis sp. nov. in cultivation in deep shade show a blue iridescence of the upper leaf surface.

Conservation status
Data Defi cient (DD; IUCN 2012). The conservation status of B. yapenensis sp. nov. is not known. The distribution and habitat information for this species is based on just one collection from Ambaidiru village in the highlands of Yapen Island, Papua, Indonesia. Although the forest around Ambaidiru village is part of the Central Yapen Natural Reserve, the establishment of road access from south to north across the island within the protected area, as well as the expansion of Ambaidiru village, may affect the population of this Begonia. More population and distribution data are required to fully assess the conservation status of this species.

Discussion
Although known only from a single collection, the authors are confi dent in the novelty of B. yapenensis sp. nov. as it differs not only in habit, but also in androecium morphology from the most similar member of Begonia sect.