Molecular taxonomy and acoustic data of the black francolin (Francolinus francolinus) support a reappraisal of the intra-Palaearctic boundary

The debate about the transition zone between eastern and western Palaearctic is still ongoing, with some zoologist recently ascribing the whole Iran – a key crossroad of faunal biodiversity – to the latter as part of the “Great Western Palaearctic”. Additional distributional and systematic information from low-vagile and sedentary taxa may help settle the dispute. For this purpose, we genotyped samples of black francolin 221 (Francolinus francolinus), a landbird distributed in the Middle East and southern Asia, comparing the genetic (affinity of individuals from the entire range at nine microsatellite loci with vocalisations characterised in a recent study.A stunning overlap emerged between the two sources of information, both indicating the occurrence of an eastern and a western cluster consisting of four and two morphological subspecies, respectively, with a divide running north to south across central Iran. Interestingly, the same scenario was found between genetically dissimilar populations of other vertebrates. Palaeoclimatic and geological data from Iran indicated an overall higher connectivity of the region thanks to milder and moister climatic conditions prior to the cold -arid climatic phase initiated by the last glacial stage and isolating most taxa to disjunct refuges. Subsequently, the temperature raise likely compounded this scenario by hampering gene flow between populations of species - black francolin included - located east and west of the Kavir and Lut deserts. Although the taxonomic significance of this split in the focal species awaits for further studies, these results produced weight for the occurrence of an eastern-western Palaearctic boundary crossing Iran longitudinally