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

Abstract

Lachenalia (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, to accommodate this species. Conversely, the inclusion of species previously classified as Polyxena 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, L. sect. Lachenalia, is further divided into 13 more-or-less diagnosable, monophyletic subsections. Keys to the sections of Lachenalia, and to the subsections of L. sect. Lachenalia, are provided.

1059. Lachenalia bolusii W.F. Barker: Asparagaceae

“…It provided strong support for a monophyletic radiation of the genus in southern Africa and a reliable foundation upon which to base a revised infrageneric classification. Despite the highly imbalanced character of this phylogeny and the high levels of homoplasy shown by most morphological characters, it was possible to propose a new infrageneric taxonomy in which the previously recognized subgenera were dispensed with, and 10 morphologically distinct, monophyletic sections ( Colliculatae , Cordatae , Ciliolatae , Linearifoliae , Cretaceae , Atrorubentes , Trichomatosae , Polyxena , Stellatae and Lachenalia ) were proposed (Duncan et al, 2022). The largest of these, section Lachenalia comprising 92 species, was further subdivided into 13 monophyletic subsections ( Nervosae , Coriaceae , Crispae , Latae , Verticillatae , Urceolatae , Oblongae , Framesianae , Angustae , Stramineae , Inflatae, Oncoraphae and Lachenalia ) .…”

“…The largest of these, section Lachenalia comprising 92 species, was further subdivided into 13 monophyletic subsections ( Nervosae , Coriaceae , Crispae , Latae , Verticillatae , Urceolatae , Oblongae , Framesianae , Angustae , Stramineae , Inflatae, Oncoraphae and Lachenalia ) . L. bolusii was retrieved within subsection Crispae as sister to L. marlothii W.F.Barker ex G.D.Duncan, a light blue‐flowered species with a disjunct distribution in Namaqualand and the Richtersveld in the north, and the Calvinia district of the western Karoo to the south (Duncan, 2012) and these are the only members of subsection Crispae , characterised mainly by their minutely crisped leaf margins (Duncan et al, 2022).…”

“…The high level of floral diversity in Lachenalia (tubular, narrowly or widely bell‐ or urn‐shaped) is probably associated with its use of diverse pollinators, with three pollination syndromes being recognized: mellitophily, ornithophily and generalist pollination, the latter including monkey beetles, blister beetles, hoverflies, march flies, butterflies and day‐flying moths (Duncan, 2012; Duncan et al, 2022). An extraordinary level of cytological variation occurs within Lachenalia , including differences in basic chromosome number, variable ploidy levels and the presence of B‐chromosomes (supernumary chromosomes) in certain species (Kleynhans et al, 2012).…”

“…ex Houtt. (Duncan, 2023;Duncan et al, 2022). Its main centre of diversity is divided between the Fynbos and Succulent Karoo biomes in the valleys and flats of the interior mountains of the 3318 (Worcester) grid, in the south-western part of the Western Cape, where 38 species occur (Duncan, 2005;.…”