Phylogeography and morphometric variation of the Spike-heeled Lark Chersomanes albofasciata complex

Abstract

The Spike-heeled Lark Chersomanes albofasciata is a peculiar, short-tailed lark confined to southern, central and East Africa. Typical of resident larks, it exhibits marked geographic variation in plumage colour, which has historically resulted in large numbers of subspecies being described. This variation was examined by sequencing 630 base pairs of the cytochrome b gene in 39 individuals and morphometric measurements of 320 birds. Nine of the 14 southern African C. albofasciata subspecies defined by Clancey in 1980 were sampled for assessing genetic variation, as well as one population from northern Namibia (C. a. boweni) and the isolated C. [a.] beesleyi population in Tanzania. Within South Africa, 16 maternal lineages were identified. The haplotype network revealed three geographically distinct haplogroups: Namaqualand, Karoo and Eastern grasslands, which did not follow past or existing subspecies ranges. Our data thus suggest incongruence between genetic variation and phenotype in South Africa. The boundaries and relationship among the phylogeographic haplogroups and morphometric measurement were similar to the closely related Long-billed Lark Certhilauda curvirostris complex suggesting similar processes during their evolutionary history. The existing subspecies designations are clearly not supported by the genetic data presented here and thus more research into this complex is required. Further research should include sampling of Spike-heeled Larks in underrepresented areas of the species’ range and the use of additional genetic markers to improve our understanding of the evolutionary history of this complex. C. [a.] beesleyi was sister to all haplotypes sampled and smaller in size than all subspecies measured. Although the status of the contentious C. [a.] beesleyi has still not been resolved, we have added morphometric data supporting its isolation from other subspecies. Its limited and isolated range warrants increased conservation efforts and we propose its recognition as an evolutionarily significant unit.