New insights into the morphology and taxonomy of the Acrocephalus baeticatus / scirpaceus species complex based on a newly found West African syntopic population.. Acrocephalus Burkina Faso

A precise knowledge on biodiversity in tropical developing countries is pivotalto address proper conservation guidelines and policies, especially when natural habitats arestrongly jeopardized by land use changes due to agriculture or industrial issues. In West Africa,Burkina Faso is a typical example of this emerging trend, and its natural or semi-natural wetlandareas are of great importance as breeding or wintering sites for many passerine species, includingthe taxonomic complex group of unstreaked reed warblers (genus Acrocephalus). The use ofmorphological characters to distinguish between A. baeticatus and A. scirpaceus occurring insyntopy, is often subtle. To shed more light on the taxonomic status of a newly found Acrocephaluscommunity in South Burkina Faso and on the reliability of the available criteria adopted toidentify members of this species complex, we here compared the morphological features ofsome specimens collected during different field expeditions and supporting our phenotypicalassessment with a molecular identification approach. Sixteen Acrocephalus specimens werecollected at a recent wetland area located South of Burkina Faso during winter. Specimens weremeasured and assigned to the species level based on the published and conventionally adoptedmorphological criteria. A COI-based DNA barcoding approach was used to confirm identification.Our integrated identification approach confirmed the occurrence of the first population ofA. baeticatus for Burkina Faso. This is geographically isolated from other West African knownpopulations. Interestingly, our results highlighted that the traditionally adopted identificationtrait, based on the emargination on the 7th primary, is not always valid to distinguish A. baeticatusfrom its conspecifics, which partly overlap also in biometric measurements. We thereforesupport the greater reliability of the ‘wing length / P9 notch’ criterion recently proposed for theidentification of Palaearctic unstreaked Acrocephalus species and its importance to separate thewintering species of Palearctic origin from the African resident ones.