Post-glacial expansion and migration-drift balance shape the genetic structure of the Dalmatian Pelican (Pelecanus crispus) across its range

Understanding range-wide genetic diversity, population structure and connectivity is fundamental for evaluating the evolutionary potential and conservation needs of a species. The Dalmatian Pelican ( Pelecanus crispus ) is a long-lived colonial waterbird, with a broad distribution from southeastern Europe to Central Asia. It experienced severe anthropogenic population declines during the 19th–20th centuries but has recently recovered following targeted conservation actions. Despite extensive ecological knowledge, its population genetics have remained unexplored. Here, we present the first comprehensive genetic assessment of the species across its range, using mitochondrial ND2 sequences and a set of microsatellite loci to quantify genetic diversity, characterize population structure, reconstruct demographic history and identify regions of conservation priority. Mitochondrial data revealed low haplotype and nucleotide diversity and a shallow genealogical history indicative of a recent post-glacial expansion from a bottlenecked maternal lineage. Bayesian skyline plot analysis suggested population growth beginning after the Last Glacial Maximum. Microsatellite diversity was uniformly low across colonies, with no private alleles, and differentiation among colonies was detectable, but weak. Bayesian clustering, F ST and D est support a continuous population structure consistent with isolation by distance, under migration-drift balance occurring from the interaction between historical bottlenecks, contemporary gene flow and recent recolonisation. Although overall gene flow appears sufficient to buffer further loss of genetic diversity, the low standing variation highlights the need for continued, coordinated conservation. Our results provide a baseline for future studies on the genetics of the species and support flyway-scale management that prioritises habitat connectivity and safeguards peripheral colonies.