A new sectional classification of Lachenalia (Asparagaceae) based on a multilocus DNA phylogeny

Lachenalia J.Jacq. ex Murray (Asparagaceae; Scilloideae; Hyacintheae) is a large and morphologically diverse genus of more than 140 bulbous species endemic to southern Africa. Previous attempts to infer a well resolved and robustly supported phylogeny of Lachenalia using Sanger sequencing of candidate loci and/or morphological characters have been largely unsuccessful. Consequently, the current infrageneric classification is artificial and there is a need to explore alternative avenues to produce a phylogenetic classification. In this paper we present a novel phylogenetic hypothesis for Lachenalia inferred using maximum likelihood and coalescent-based species tree estimation (ASTRAL) as applied to 378 hybrid-enrichment loci. Our tree is well resolved and well supported, providing strong support for a monophyletic radiation of the genus in southern Africa and a solid foundation for a revised infrageneric classification. The well-supported placement of L. isopetala Jacq. as sister to Lachenalia + Massonia supports the establishment of a new monotypic genus, Pseudolachenalia G.D.Duncan, to accommodate this species. Conversely, the inclusion of species previously classified as Polyxena Kunth within the Lachenalia clade supports the transfer of these species to Lachenalia. Within Lachenalia, the delimitation of subgenera and sections is complicated by the highly imbalanced character of the phylogeny and by the high levels of homoplasy shown by most morphological characters traditionally used to delimit species in this group. Nonetheless, we propose an infrageneric taxonomy comprising 10 morphologically distinct, monophyletic sections. The largest of these, section Lachenalia, is further divided into 13 more-or-less diagnosable, monophyletic subsections. Keys to the sections of Lachenalia, and to the subsections of section Lachenalia, are provided.