Background/Aims:
The Pilbara region of Western Australia is home to 15 described native freshwater fishes, with phylogenetic data continuing to uncover cryptic diversity within the region’s rugged gorges and seasonal rivers. Among the named species are two representatives from Hypseleotris: the widespread empire gudgeon H. compressa, and the endemic golden carp gudgeon H. aurea, listed as Endangered by the IUCN. In 2024, specimens appearing to be H. aurea were collected from a tributary of the Fortescue River in Karijini National Park. The collection was significant as the species was previously thought to be restricted to the Gascoyne and Murchison rivers in the southern Pilbara, separated from the Fortescue River by several major catchments and a linear distance of over 400 km. Given their isolated occurrence, we undertook molecular analysis of the specimens, aiming to determine their phylogenetic relationship to other Western Australian Hypseleotris.
Methods:
Ethanol-preserved specimens were examined under dissecting microscope, with features compared against the key to Western Australian Hypseleotris in Shelley et. al. (2023)1. DNA was extracted from dorsal fin clippings using the QIAGEN DNeasy Blood and Tissue Kit. Two primer sets (GOBY L4919 and GOBY H5513; HYPSL5464 and GOBY H6064) were used to amplify two overlapping segments of the mitochondrial ND2 (NADH dehydrogenase subunit 2) gene. Amplified PCR products were sequenced using bidirectional Sanger sequencing at AGRF Perth, with comparisons made against available Hypseleotris sequences on GenBank.
Results:
Morphological and phylogenetic analyses found that the specimens were indeed close to Hypseleotris aurea. However, there was relatively strong genetic variance from southern H. aurea populations, being 9.0% divergent from those of the Gascoyne River across 1,047bp of the ND2 mtDNA region.
Conclusion:
Further molecular and taxonomic work is required, however, there is strong preliminary evidence to suggest our specimens may represent a distinct species, or at least a genetic variant of H. aurea, long isolated from southern populations. Regardless, we consider there to be a relatively high conservation risk to the population, given its restricted range in a high-traffic tourist area, and recent anecdotal reports of declining water levels within Karijini National Park.