Character evolution in Begonia sections Gireoudia and Weilbachia - a phylogenetic approach

Abstract

The pattern of morphological character distributions in a plant group can show how the species have evolved and adapted to different environmental conditions. Neotropical Begonia sections Gireoudia and Weilbachia contain a morphologically divergent array of species. This study used sequences from 46 species at three non-coding chloroplast regions (ndhA intron, ndhF-rpl32 spacer and rpl32-trnL spacer) to generate a phylogeny using Bayesian analysis. Abstract. Ten morphological characters were measured and mapped onto this phylogeny. The characters generally had low phylogenetic signal. Hybridisation or rapid morphological evolution may account for this. However, petiole width, stomatal clustering and leaf perimeter over area showed a moderate, significant, phylogenetic signal, implying a degree of niche conservatism. Some characters, particularly petiole width, correlated with some temperature and precipitation data suggesting adaptations to climatic conditions. This study also highlighted that Weilbachia do not form a monophyletic group and therefore should not be classed as a separate section. In the future nuclear DNA needs to be sequenced to address whether hybridisation has occurred and confirm phylogenetic relationships.