干旱区生态环境知识资源中心

Aim Savanna occupies a substantial part of Africa, being distributed around the two major tropical rain forest blocks in what is referred to as the Savanna Belt. Our current understanding of the genetic structure within species distributed across the Savanna Belt is primarily derived from mammalian taxa, studies of which have revealed a suture zone or transition between northern and east/southern Africa clades in south-western Kenya and north-western Tanzania. We conduct a phylogeographic study of the fiscal shrike (Lanius collaris), a polytypic species distributed across the Savanna Belt of Africa and for which morphological and vocal data are in agreement with the suture zone recovered for mammalian taxa, to test the hypothesis of a spatially congruent genetic break across several taxa, including birds.

Location Africa, south of the Sahara.

Methods We analysed DNA sequences recovered from four loci (one mitochondrial, two autosomal and one Z-linked) in 66 individuals, representing all recognized subspecies, as well as putatively closely related species. We make use of a combination of tree-building and population genetic methods to investigate the phylogeographic structure of the fiscal shrike across Africa.

Results The fiscal shrike consists of two primary lineages with a strong geographic component: a northern group distributed from southern Tanzania to Senegal, and a southern group distributed from Botswana/Zambia to South Africa with isolated populations in Tanzania and northern Malawi. Unexpectedly, Souza’s shrike (L. souzae) was nested within L. collaris, as the sister group of the southern group. The positions of Mackinnon’s shrike (L. mackinnoni) and that of the Sao Tome shrike (L. newtoni) were variable, being either nested within the fiscal shrike or sister to the L. collaris-L. souzae clade. Our divergence time analyses suggest that the Lanius collaris species complex started to diversify around 2.2 Ma.

Main conclusions Our study reveals a distinct biogeographic pattern for a savanna distributed species in Africa, with the transition between the two primary genetic lineages occurring at a latitude of c. 15-16 degrees S, 10 degrees S further south than shown elsewhere for several mammalian species.