BARLOWS LARK - A NEW SPECIES IN THE KAROO LARK CERTHILAUDA-ALBESCENS COMPLEX OF SOUTHWEST AFRICA

The Karoo Lark Certhilauda albescens complex, endemic to southwest Afr ica, is characterized by regional phenotypic variation, Recent consens us has been to recognize two species, Dune Lark Certhilauda erythrochl amys and Karoo Lark Certhilauda albescens, but intermediate forms arou nd the mouth of the Orange River have resulted in some authors treatin g it as a single polytypic species complex. We reexamined the status o f taxa in this group by sequencing a segment of the mitochondrial DNA cytochrome b gene. Most samples were from the area around the mouth of the Orange River, where there is considerable local phenotypic variat ion. Our results indicate that the complex: comprises three species, K aroo Lark, Dune Lark and Barlow's Lark Certhilauda barlowi, separated by 1.9-5.5% sequence divergence, There were no sequence differences am ong described subspecies, but there was limited variation among Dune L ark individuals (sequence divergence values 0.2-0.4%), The Red Lark Ce rthilauda burra is closely related to the Karoo Lark complex; indeed, it may be that Karoo Lark is the ancestral form, There was morphologic al (biometrics and plumage) and behavioural (male display song structu re) support for the recognition of Barlow's Lark as a separate species . Species ranges within the complex are allopatric or narrowly parapat ric, and they occur in different habitats and climatic condition, Disc riminant function analysis correctly identified 99% of skins assigned to taxa based on range, but a few individuals collected in the contact zone between Karoo and Barlow's Larks exhibited intermediate phenotyp es, and further investigations are warranted to search for evidence of hybridization. The newly recognized Barlow's Lark has a maximum range of 18,000 km(2), It appears to have disappeared from heavily grazed f arms around Aus, southern Namibia, and occurs almost exclusively in di amond mining areas, where domestic livestock are excluded, Changes to land use practices which reduce vegetation cover could seriously impac t this species.