Molecular Phylogeny and Morphological Divergence in Thesium L. (Santalaceae)

The protection of species and ecosystems is of concern to most naturalists, and accurate information about organisms is a prerequisite to successful conservation strategies. Thesium (Santalales: Santalaceae) is a large (350 species) genus of root hemiparasitic subshrub species having a principally Old-World distribution with its greatest diversity in southern Africa (about 185 but poorly studied, possibly because of its drab morphology. Many species in the genus are Red Listed as data deficient, least concerned and others are endangered partly due to unresolved phylogenetic relationships. The goal is to address these shortfalls and to initiate a comprehensive analysis of the phylogenetics based on morphological and molecular evidence. To achieve these, 322 accessions of 115 species at herbaria and our field collections were studied. Preliminary distribution data indicated that most species were observed to be in the fynbos biome with a few renosterveld and coastal form (T. fruticulosum), forest edges (T. strictum) and only T. carrinatum var. pallidum occur above 1200 m. Morphological data matrix containing 64 qualitative and quantitative characters was subjected to parsimony character reconstruction. To buttress the resultant trees, these accessions were all included in a phylogenetic analysis. Both Chloroplast (trnL-trnF, MatK and rpL32) and gene marker (ITS) data resolved Thesium as paraphyletic genus relative to putative new genus - Zeyhri with high posterior probability and bootstrap support. ITS sequence data placed hystrix as sister to a large Thesidium clade, but with weak support.