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Journal article
Unique Population or Unique Species? Genetic Insights Into the Pygmy Freshwater Crocodiles of Northern Australia
Ecology and evolution, Vol.16(8), e74055
2026
PMID: 42540546
Abstract
Isolated populations of Australian freshwater crocodiles ( Crocodylus johnstoni ) in few elevated, rocky escarpment areas of the Northern Territory of Australia reach sexual maturity earlier and generally have an adult size half that of their downstream counterparts. There is debate over whether these “pygmy” or “dwarf” crocodile populations are the result of extreme phenotypic plasticity or the origins of a unique species through peripatric speciation. This debate is of conservation concern as these populations face immediate threats from invasive species and climate change, and species classification can affect conservation management strategies. We used mitochondrial DNA control region and cytochrome b sequences to investigate whether mtDNA haplotype variation supports any evidence of speciation between the pygmy and standard‐size freshwater crocodiles. Additionally, we used genotyping by sequencing (dd‐RADseq) to examine genetic clustering. Separated and concatenated control region and cytochrome b haplotypes were shared between pygmy and standard‐size crocodile populations. Principle Component Analysis and STRUCTURE analyses on dd‐RADseq data showed pygmy and standard‐size crocodiles cluster by geographic location as much as by phenotype. We found no clear and objective genetic evidence to suggest that the pygmy freshwater crocodiles should be considered a separate species from any other population of the standard‐size crocodiles. However, the isolation and environmental adaptability of these unique pygmy freshwater crocodile populations make them ecologically unique and valuable for conservation, and worth safeguarding against potential threats. There is debate over whether isolated populations of “pygmy” Australian freshwater crocodiles are a unique species. This is a conservation concern as these populations face unique challenges. We found some population differences which support these populations as being ecologically unique and valuable for targeted conservation.
Details
- Title
- Unique Population or Unique Species? Genetic Insights Into the Pygmy Freshwater Crocodiles of Northern Australia
- Authors/Creators
- Katherine Brittain - The University of SydneyTorre Muhlbach - The University of SydneyRui Cao - The University of SydneyJose Luis Mijangos - The University of SydneyDean Yibarbuk - Warddeken Land Management LtdErin O'Brien - Parks and Wildlife ServiceRuchira Somaweera - Murdoch UniversityNancy N. FitzSimmons - Griffith UniversityJaime Gongora - The University of Sydney
- Publication Details
- Ecology and evolution, Vol.16(8), e74055
- Publisher
- British Ecological Society and John Wiley & Sons Ltd.
- Identifiers
- 991005909772707891
- Copyright
- © 2026 The Author(s).
- Murdoch Affiliation
- School of Environmental and Conservation Sciences
- Language
- English
- Resource Type
- Journal article
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