Genomic contamination threatens endangered Milky Storks in Singapore

Researchers from NUS and Wildlife Reserves Singapore (WRS) have discovered that the endangered Milky Storks’ conservation is threatened through cross-breeding with Painted Storks.

The Milky Stork is a native, endangered wading bird found in parts of Southeast Asia. Its global population numbers about 1,500 individuals in the wild. The region around Singapore and Johor, Malaysia may hold up to about seven to 10 per cent of the global wild population. Since the late 1980s, Milky Storks and their more widespread cousins, Painted Storks, have been held together in captivity in Singapore and Malaysia. This has led to inadvertent cross-breeding or hybridisation between the two stork species whenever the two have been kept in the same enclosure. The Milky Storks are distinct from Painted Storks in absence of black breast band, absence of pink flush in its plumage, and completely white upper wing coverts. However, the hybridised storks display intermediacy in these phenotypic traits. A few of these hybrids escaped from captivity, potentially threatening the genomic composition of Milky Storks in the wild. However, the extent of this threat has not been clear.

A research team led by Prof Frank RHEINDT, from the Department of Biological Sciences, NUS in partnership with WRS has discovered significant genomic contamination in the genetic composition of local Milky Storks due to the introduction of alien alleles from Painted Storks into their native gene pool. Through this process, endangered species with very small populations can eventually be absorbed into the genome of the more widespread species. The researchers analysed the DNA of tissue samples from 46 Milky Storks from Singapore (both wild and captive) in their research. They also found that the genomic composition of almost half of the sampled storks continued to remain unaffected by genetic infiltration from the Painted Stork. This finding indicates that prioritisation of conservation efforts may prevent further genomic erosion of this globally endangered species.

Prof Rheindt said, “We found that admixed Milky Storks can often be identified by a combination of intermediate phenotypic traits. These Milky Storks could be identified and isolated from the others to prevent cross-breeding and further genetic erosion. This endangered species should receive the conservation attention that it deserves.”

Figure shows a stork hybrid (middle) with genetic traits from both the Milky Stork (left) and the Painted Stork (right). [Image Credit: Eddy LEE Kam Pang (left), Debjyoti GHOSH (middle) and Nawin TIWARY (right)]

Reference

Baveja P; Tang Q; Lee JGH; Rheindt FE*, “Impact of genomic leakage on the conservation of the endangered Milky Stork” BIOLOGICAL CONSERVATION Volume: 229 Pages: 59-66. DOI: 10.1016/j.biocon.2018.11.009. Published: 2018.