Journal Articles

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    Leech breach: a first record of the invasive freshwater leech Helobdella europaea (Hirudinea: Glossiphoniidae) in Fiji
    (CSIRO Publishing, 2023-07-03) Rashni B; Brown KT; McLenachan PA; Lockhart PJ; Southgate PC; Lal MM; Calver M
    Context: The freshwater flat leech Helobdella europaea Kutschera, 1987 is a small annelid indigenous to South America. This invasive species feeds on the haemolymph of host aquatic invertebrates, with occurrences reported from Europe, USA, Taiwan, North Africa, Hawai'i, Australia and New Zealand. A large number of individuals were discovered in the Ba River catchment, Fiji, during a 2015-2020 freshwater biodiversity survey, raising concerns of potential impacts on endemic Fijian aquatic invertebrate fauna and ecosystem integrity. Aims: To facilitate assessments of its spread and ethology, this study employed morphological and phylogenetic analyses for verification of taxonomic identity. Methods: Phylogenetic trees were constructed using a 658 bp fragment of the mitochondrial DNA cox1 (COI) gene. The first complete mitochondrial genome sequence of H. europaea was also determined using selective multiple displacement amplification and Oxford Nanopore Technology to provide a reference for future comparative analyses and source tracking of spread to other regions. Key results: Morphological and COI analyses identified all Fijian leech specimens collected (n = 16) as H. europaea, reporting the first occurrence of this species on a south-west Pacific Island. The complete mitochondrial genome was sequenced. Conclusions: Confirmation of its presence in Fiji is a national biosecurity concern and will guide the Biosecurity Authority of Fiji and national agencies in further ecosystem assessment and response strategies. Implications: With the complete mitochondrial genome of H. europaea now available, transmission pathway traceability is possible in other regions where this species may be detected.
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    Regional patterns of mtDNA diversity in Styela plicata, an invasive ascidian, from Australian and New Zealand marinas
    (CSIRO PUBLISHING, 7/03/2013) Torkkola J; Riginos C; Liggins L
    The ascidian Styela plicata is abundant in harbours and marinas worldwide and has likely reached this distribution via human-mediated dispersal. Previous worldwide surveys based on mitochondrial cytochrome oxidase one (COI) sequences have described two divergent clades, showing overlapping distributions and geographically widespread haplotypes. These patterns are consistent with recent mixing among genetically differentiated groups arising from multiple introductions from historically distinct sources. In contrast, a study of Australian S. plicata using nuclear markers found that population differentiation along the eastern coast related to geographic distance and no evidence for admixture between previously isolated genetic groups. We re-examined the genetic patterns of Australian S. plicata populations using mtDNA (CO1) to place their genetic patterns within a global context, and we examined New Zealand populations for the first time. We found that the haplotypic compositions of Australian and New Zealand populations are largely representative of other worldwide populations. The New Zealand populations, however, exhibited reduced diversity, being potentially indicative of a severely bottlenecked colonisation event. In contrast to results from nuclear markers, population differentiation of mtDNA among Australian S. plicata was unrelated to geographic distance. The discrepancy between markers is likely to be a consequence of non-equilibrium population genetic processes that typify non-indigenous species. © 2013 CSIRO.