History of the Crested Lark in the Mediterranean region as revealed by mtDNA sequences and morphology

The Crested Lark has a very complex taxonomy, partly as a result of a strong variation in plumage ground color seemingly linked with environmental factors. However, large variations in body size and bill shape further complicate the situation in the Maghreb. In this paper, we first present a set of hypotheses to explain patterns of morphological variation around the Mediterranean Sea. A phylogeographical analysis covering all major biogeographical areas in the species’ range is then performed to test these scenarios. Three mtDNA groups with distinct geographical distribution were identified. The randonii clade (= G. (c.) randonii) is endemic from central Maghreb and is phylogenetically basal relative to cristata and senegallensis. These two latter groups are much more widespread. The cristata clade is found in NW Morocco, throughout Europe and W Asia and in NE Africa, while senegallensis regroups the populations sampled in the Western Sub-Saharan Africa and in NE Maghreb (E Algeria, Tunisia). A combination of genetic and paleoenvironmental evidences supports a scenario of allopatric differentiation of these two lineages outside the Maghreb, with subsequent range expansion leading to their secondary presence in the Maghreb. However, the alternative hypothesis of differentiation in two, or even three separate Maghreb refuges cannot be completely dismissed with the present data. Interestingly, the Sahara desert and the Gibraltar Strait did not act as permanent barriers to dispersal in this species. In addition, the populations in the Maghreb are consistently longer-billed than their closest relatives, suggesting a role for natural selection or phenotypic plasticity.