Genomics Reveals Anthropogenic Fragmentation and Introgression in a Highly Endangered New Zealand Freshwater Fish
Jonathan M. Waters, Daniel C. Jack, Meeran Hussain, Tania M. King, Graham A. McCullochABSTRACT
Aim
The endemic freshwater fish fauna of New Zealand has been severely impacted by drainage modifications and the introduction of salmonid predators. We aim to test for the impacts of anthropogenic population fragmentation on genetic diversity in a critically endangered endemic fish, to inform future conservation management of this species.
Location
Teviot River and surrounding drainages, South Island, New Zealand.
Methods
We generate and analyse a genome‐wide data set comprising 47,754 SNPs across 275 Galaxias specimens to assess genetic diversity across the range of a critically endangered freshwater fish, G . ‘Teviot’. We conduct phylogenetic, STRUCTURE and genetic diversity analyses to evaluate the evolutionary relationships of Teviot River populations in the context of major anthropogenic river drainage alterations in this region.
Results
Our analysis reveals genetic divergences linked to anthropogenic population fragmentation, with the deepest phylogeographic splits within G . ‘Teviot’ correlated with the first Lake Onslow dam (constructed in 1890). We also show that subsequent drainage modifications (water‐race connections) are associated with the apparent introgressive spread of alleles from a newly recognised candidate taxon, G . ‘Manor Burn’, into upper Teviot populations. Counterintuitively, the Lake Onslow dam appears to have buffered lower Teviot populations from this anthropogenic introgression.
Main Conclusions
We identify key genetically diverse, yet non‐introgressed, populations of G . ‘Teviot’ as suitable sources for potential translocations to genetically safeguard this critically endangered fish species.