Impact of genomic leakage on the conservation of the endangered Milky Stork

Endangerment and extinction of threatened populations can often be accelerated by genomic contamination through infiltration with alien alleles. With a growing anthropogenic footprint, many such hybridization events are human-mediated. The Milky Stork (Mycteria cinerea) is one such species whose genomic composition is threatened by human-mediated hybridization with its sister taxon, the Painted Stork (Mycteria leucocephala). A comprehensive investigation of the stork population in Singapore using three complementary population-genomic approaches revealed a large proportion of hybrids that have undergone several generations of genomic leakage from Painted Storks and fall along a genetic cline that closely mirrors a phenotypic cline from pure Milky to pure Painted. Although originating from a limited number of introduced Painted Storks, these hybrids are now an integral part of both the wild and captive Singaporean and southern peninsular Malaysian stork population. Genetically informed conservation management including the isolation of hybrids in captivity and a strict removal of hybrids from the wild along with a release of genetically pure Milky Storks is imperative for continued survival. Similar approaches must become routine in endangered species conservation as human-mediated hybridization increases in volume.