Cryptic biodiversity in Australian freshwater fishes
The resolution of cryptic species diversity within H. klunzingeriaccords with the trend of finding new candidate species in Australian
freshwater fish guided by molecular data (e.g., Adams et al., 2014;
Hammer et al., 2019; Unmack et al., 2022). Such data can not only reveal
the presence of cryptic species but can also uncover nuanced evidence
for admixture and introgression that was often not detectable prior to
the advent of detailed genomic datasets and the coupling of ordination
and tree-based approaches. The application of this modern molecular
approach to taxonomic uncertainty in H. klunzingeri has
identified the presence of additional candidate species in this nominal
taxon. Moreover, as in our companion study of Australian smelt
(Retropinna spp.; Unmack et al., 2022), additional morphological,
phenotypic or ecological data are not required in most cases to validate
the identified candidate species per se (the exceptions being KW+
versus KS in Hypseleotris , and COO versus MTV inRetropinna ). However, such data remain the foundation for formal
description and naming of candidate species and are of course valuable
for addressing other questions about the biology of individual species,
whether formally named or not.