Chloroplast and nuclear DNA exchanges among Begonia sect. Baryandra species (Begoniaceae) from Palawan Island, Philippines, and descriptions of five new species

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.

A molecular phylogeny of Southeast Asian Cyrtandra (Gesneriaceae) supports an emerging paradigm for Malesian plant biogeography

“…This is in marked contrast to previous phylogenetic studies of Cyrtandra, where extensive hybridisation and/or incomplete lineage sorting has been reported, principally in Hawaii (Pillon et al 2013, Johnson et al 2019 but also in the recent radiation of the genus in the Pacific (Johnson et al 2017). This also differs from the ecologically and biogeographically similar genus Begonia, where the high prevalence of hybrid events is considered to be an important factor driving genomic change and species evolution (Hughes et al 2018). A recent study of reproductive isolation in four species of Hawaiian Cyrtandra showed that boundaries between sympatric Cyrtandra species are maintained predominantly through postzygotic barriers (Johnson et al 2015).…”

In memoriam Ching-I Peng (1950–2018)—an outstanding scientist and mentor with a remarkable legacy

“…5) in the Experimental Greenhouse of BRCAS, with duplication in the Dr. Cecilia Koo Botanic Conservation Center (KBCC). The living Begonia collection in BRCAS and KBCC is one of the largest in the world (Hughes and Peng 2018).…”

“…Following the completion of the FOC treatment of Begoniaceae, Dr. Peng initiated field studies of Begonia in India (1 trip), Indonesia (2 trips), Malaysia (3 trips), the Philippines (5 trips), Thailand (3 trips), and Vietnam (3 trips), and visited public and private collections of Begonia in Australia, Denmark, France, India, Japan, Netherlands, UK, and the United States. BRCAS's expanding living collection of Begonia became an invaluable asset for both research and conservation, especially with its many collections from type localities (Hughes and Peng 2018). Dr. Peng constantly received requests for literature, species identification, advice on Begonia cultivation, as well as plant material exchange.…”

A revision of Begonia sect. Petermannia on Sumatra, Indonesia

“…Our phylogeny based on nuclear ribosomal ITS sequences presented in this paper shows clades with a mix of inflorescence types, habits and indumentums and does not highlight a clear pattern of character evolution. In addition, chloroplast data has a differing phylogenetic history to nuclear markers (Thomas et al 2012;Hughes et al 2018a), making a reliable sectional classification difficult. In Sumatra at least, it seems our only option is to delimit Petermannia by removing the species with the full suite of characters placing them in Begonia sect.…”