Abstract
The Philippine island of Palawan is highly biodiverse. During fieldwork there in 2011 & 2014 we found five unknown species in the large genus Begonia. The species are similar in their rhizomatous stems, four-tepaled flowers, inferior two- or three-locular ovaries with bilamellate placentas, and are assignable to Begonia sect. Baryandra. Our observations support the recognition of these as five new species endemic to Palawan: B. elnidoensis, B. gironellae, B. quinquealata, B. tabonensis and B. tenuibracteata which are described here. The five new species were added to phylogenies based Bayesian analysis of nrDNA (ITS) and chloroplast DNA (ndhA, ndhF-rpl32, rpl32-trnL, trnC-trnD), along with 45 other allied ingroup species. A majority of the species show incongruent positions in the two phylogenies, with evidence of prevalent chloroplast capture. Models show chloroplast capture is more likely in plant populations with high levels of inbreeding following a reduction in selfing rate after hybridisation; we suggest that this is a possible explanation for the massive amount of chloroplast exchange seen in our phylogeny, as Begonia species often exist as small isolated populations and may be prone to inbreeding depression. Our data also indicate a level of nuclear genetic exchange between species. The high prevalence of hybrid events in Begonia is potentially an important factor in driving genomic change and species evolution in this mega-diverse genus.
Highlights
Begonia elnidoensis was compared to B. wadei Merr., B. gironellae to B. cleopatrae C.Coyle, B. quinquealata to B. suborbiculata Merr., and both B. tenuibracteata and B. tabonensis were compared to B. mindorensis
The ITS electropherograms for terminals B. nigritarum3, B. tabonensis, B. wadei, B. woodii1 and B. woodii2 showed some polymorphism towards the end of the reads, good sequence data was obtained for all the alignment for these taxa with the exception of portions of the 5.8S gene and the ITS2 spacer
The five new species described here show that Palawan is biodiverse and underexplored; four of the species are from nearby localities in the El Nido municipality, and so further exploration in other parts of the island is likely to reveal additional novelties
Summary
Palawan is the only island province in the Philippines with more than 50% of its forest cover intact and it has been estimated that the island contains 1,522 species of flowering plants with. During 2017 we are grateful for the support of players of People’s Postcode Lottery towards our scientific research
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