biostudies-literatureUnknown14(5)Jense CCommonwealth Scientific and Industrial Research OrganisationUniversity of TasmaniaIdentification of taxonomically cryptic species is essential for the effective conservation of biodiversity. Freshwater-limited organisms tend to be genetically isolated by drainage boundaries, and thus may be expected to show substantial cryptic phylogenetic and taxonomic diversity. By comparison, populations of diadromous taxa, that migrate between freshwater and marine environments, are expected to show less genetic differentiation. Here we test for cryptic diversity in Australasian populations (both diadromous and non-diadromous) of two widespread Southern Hemisphere fish species, <i>Galaxias brevipinnis</i> and <i>Galaxias maculatus</i>. Both mtDNA and nuclear markers reveal putative cryptic species within these taxa. The substantial diversity detected within <i>G. brevipinnis</i> may be explained by its strong climbing ability which allows it to form isolated inland populations. In island populations, <i>G. brevipinnis</i> similarly show deeper genetic divergence than those of <i>G. maculatus</i>, which may be explained by the greater abundance of <i>G. maculatus</i> larvae in the sea allowing more ongoing dispersal. Our study highlights that even widespread, 'high-dispersal' species can harbour substantial cryptic diversity and therefore warrant increased taxonomic and conservation attention.Ecology and evolutione11201https://www.ebi.ac.uk/biostudies/studies/S-EPMC11116845biostudies-literatureCryptic diversity within two widespread diadromous freshwater fishes (Teleostei: Galaxiidae).PMC11116845Jense CAdams MBurridge CPHardie SADeagle BEWaters JMBarmuta LARaadik TAMorgan DLfalseCryptic diversity within two widespread diadromous freshwater fishes (Teleostei: Galaxiidae).Identification of taxonomically cryptic species is essential for the effective conservation of biodiversity. Freshwater-limited organisms tend to be genetically isolated by drainage boundaries, and thus may be expected to show substantial cryptic phylogenetic and taxonomic diversity. By comparison, populations of diadromous taxa, that migrate between freshwater and marine environments, are expected to show less genetic differentiation. Here we test for cryptic diversity in Australasian populations (both diadromous and non-diadromous) of two widespread Southern Hemisphere fish species, <i>Galaxias brevipinnis</i> and <i>Galaxias maculatus</i>. Both mtDNA and nuclear markers reveal putative cryptic species within these taxa. The substantial diversity detected within <i>G. brevipinnis</i> may be explained by its strong climbing ability which allows it to form isolated inland populations. In island populations, <i>G. brevipinnis</i> similarly show deeper genetic divergence than those of <i>G. maculatus</i>, which may be explained by the greater abundance of <i>G. maculatus</i> larvae in the sea allowing more ongoing dispersal. Our study highlights that even widespread, 'high-dispersal' species can harbour substantial cryptic diversity and therefore warrant increased taxonomic and conservation attention.2024-01-01T00:00:00Z2024 May2026-06-01T18:57:37.882Z2025-08-27T03:07:34.992ZS-EPMC111168453879938610.1002/ece3.11201