The population genetics and origin of invasion of the invasive Asian paddle crab, Charybdis japonica (A. Milne-Edwards, 1861) (Brachyura: Portunidae) in north-eastern New Zealand

Abstract

Charybdis japonica is a recently established invasive crab in north-eastern New Zealand that is native to East Asia. Since its detection in 2000, C. japonica has spread to adjacent estuaries from the introduction site at the Ports of Auckland and established 127 km north in Whangarei Harbour. We assessed the invasion history from comparisons of genetic population diversity and mixed-stock analysis from the mitochondrial control region and nuclear ribosomal internal transcribed spacer-1, to describe the invasive population’s genetic structure, infer a possible source of origin and hypothesize the composition of the founding colonists. High diversity and distinct genetic structuring were found within and among native localities from Japan, China, Taiwan and South Korea. Crabs collected at New Zealand locations (Auckland, Whangaparaoa and Whangarei) had lower diversity and were genetically homogenous. This indicated C. japonica experienced a bottleneck on colonization, but the resultant founder effects have not prevented C. japonica from establishing and spreading along New Zealand’s north-eastern coast. Among the sampled native localities, mixed-stock and multidimensional scaling analyses revealed Japan as the most likely source of the New Zealand invasion. The presence of three mitochondrial haplotypes and five ITS-1 alleles identified from the earliest samples in 2002 suggested that the founding New Zealand population descended from as few as three individuals. Evidence also suggests the occurrence of a second invasion event into Whangarei, New Zealand. Our study has provided the baseline for a more precise examination of Japan as the source of the invasive C. japonica population in New Zealand and suggests the importance of this recurring invasion pathway.