Common Fiscal Lanius collaris is a polytypic shrike species widely distributed across the savannah belt of sub-Saharan Africa. Consisting of seven subspecies arranged into four main lineages, with a north-south divide separating the two major clades.
A new analysis of all the subspecies and related species has been performed which concludes that there is a much different arrangement of forms, if we are to be true to the evolutionary history of the group.
Using four gene sequences from both mitochondrial and nuclear sources, the researchers found that there were indeed northern and southern major lineages, but that this divided and grouped many of the shrike species south of the Sahara. Souza's Shrike, a species which differs from Common Fiscal quite substantially in its plumage - and is also composed of three recognised subspecies - was found to be part of the southern clade of the latter species, which otherwise has little diversification. A northern group found by their analysis had three lineages that were strongly divergent.
The authors recommend that Souza's Shrike be maintained as a species as it occurs in sympatry with L c capelli in northern Malawi without interbreeding, and is distinct in plumage. However, the strong mitochondrial divergence between the northern and southern clades is greater than than that between most commonly recognised shrike species, and so they suggest that the current Common Fiscal is split into two: Northern Common Fiscal (comprising the subspecies capelli, humeralis and smithii) and Southern Common Fiscal (including aridicolus, collaris, marwitzi and pyrrhostictus). The subspecies humeralis at least may also be distinctive enough from the rest of the northern group to be regarded as a species in its own right, but the authors stop short at this suggestion.
Fuchs, J, Crowe, T M and Bowie, R C K. 2011. Phylogeography of the fiscal shrike (Lanius collaris): a novel pattern of genetic structure across the arid zones and savannas of Africa. Journal of Biogeography doi:10.1111/j.1365-2699.2011.02545.x