Morphological and molecular data support recognition of Spergularia quartzicola (Caryophyllaceae) as a new species endemic to South Africa

Abstract

A new species, Spergularia quartzicola, is described from the quartz outcrops of Knersvlakte (Namaqualand, South Africa). It was sometimes confused with S. media because of perennial habit and white flowers, but the new species differs by the subshrubby, strongly woody at base, habit (vs. herbaceous, suffruticose at the base); the leaves with a long mucro and stipules narrowly triangular and acuminate (vs. leaves with minute or absent mucro, and stipules broadly triangular and not acuminate); the flowers with styles fused in a long column (vs. styles entirely free), and the seeds with deeply and irregularly lacerate wing (vs. wing entire or slightly eroded). This combination of characters is unique among the known South African relatives. Our trnL-trnF and 5.8-ITS2 phylogenetic trees place S. quartzicola together with the South African S. glandulosa and S. namaquensis in an unresolved clade, which is far from the group of S. media. Furthermore, the outstanding morphological, ecological and chorological divergence exhibited by S. quartzicola support its recognition at species rank. According to the data presented here, S. quartzicola should be considered an edaphic specialist, which might have arisen following ecological diversification on Knersvlakte quartz outcrops, as it occurred in other taxa endemic to that territory.