PHYLOGENETIC RELATIONSHIPS OF THE TRIBE NEOSPARTONEAE (VERBENACEAE) BASED ON MOLECULAR DATA

Abstract

Neospartoneae are a small tribe in Verbenaceae, native to temperate South America and comprising seven species in three genera: Diostea, Lampayo, and Neosparton. Diostea and Neosparton share an ephedroid habit and the presence of a staminode. Diostea and Lampayo share a schizocarpous fruit and bilobed stigma. Previous chloroplast DNA phylogenetic studies first identified Neospartoneae as a clade. However, evolutionary relationships within Neospartoneae remain unclear. In this study, nine loci from both chloroplast and nuclear genomes were used to reconstruct phylogeny with almost complete taxon sampling. Maximum likelihood and Bayesian analyses were conducted using single-locus and concatenated datasets to generate gene trees. A species tree was reconstructed by Bayesian multispecies coalescent analyses. The generic relationships are well resolved and confirm the monophyly of the Neospartoneae and each genus. The topologies show that Neosparton is sister to a clade comprised of Diostea and Lampayo. This study presents a first species-level phylogeny of Neospartoneae and provides insight into morphological character evolution of this tribe. The presence of a staminode shared by Diostea and Neosparton, and dry schizocarpous fruits shared by Diostea and Lampayo, are inferred to be plesiomorphic traits in Neospartoneae and not indicative of close relationship. The ephedroid habit and curved corolla tubes shared by Diostea and Neosparton may have evolved in the common ancestor of Neospartoneae and subsequently reversed in the ancestor of Lampayo, or have evolved in parallel in the two genera.