Revealing cryptic lineages: genetic structure and conservation units in the Eurasian Stone-curlew (Burhinus oedicnemus)

Birds with parapatric distribution often develop distinct subspecies over time, which exhibit morphological, behavioral, or genetic diferences in response to local environmental pressures. The Eurasian Stone-curlew (Burhinus oedicnemus) is a migratory steppe bird species of conservation concern in Europe with fve subspecies traditionally recognized by morphological and ecological features. Previous genetic studies have only partially clarifed their diferentiation. To further investigate the genetic structure of this species and assess the molecular support for subspecies divisions, we genotyped 274 individuals sampled across the full distribution range of all fve traditionally recognized subspecies using 22 polymorphic microsatellite (STR) loci. The inclusion of samples from previously unsampled areas (Morocco, Portugal, Jordan, France, and Kazakhstan) revealed new patterns of genetic variation and ancestry. Clustering methods applied on STR data indicated that the saharae subspecies, previously considered a single taxon across the southern Mediterranean basin, including North Africa, is genetically divisible into two distinct units. The eastern subspecies harterti, never investigated before, showed a clear distinct genetic identity. Overall, our results indicate the existence of six genetically diferentiated units, some of which are not aligned with current subspecies delineation. These fndings highlight complex patterns of ancestry and gene fow within the species. Given the expected impact of climate change and ongoing biodiversity loss on (pseudo-)steppe habitats, the study provides critical information for refning conservation strategies for the Stone-curlew inhabiting these threatened ecosystems.