A preliminary study of the utility of sequences from two mitochondrial protein coding genes for phylogeographic studies of marron (Cherax cainii) from southwest of western Australia.

Abstract

Marron, Cherax tenuimanus and Cherax cainii (Austin) being two of the largest freshwater crayfish species in the world, are highly sought after by recreational anglers and form the basis of an expanding aquaculture industry in western Australia. This study investigates the potential for using mitochondrial protein coding gene regions for studying geographic patterns of genetic divergence among marron populations. Partial sequences of Cytochrome b (Cyt b) (471 bp) and Cytochrome Oxidase I (COI) (600bp) gene regions were obtained from marron representing 13 populations from southwest Western Australia, and from Kangaroo Island, South Australia. Two data sets that derived from Cyt b and COI gene regions showed significant phylogenetic signal. Within C. cainii, twelve COI and ten Cyt b haplotypes were observed from the 14 locations with little intrapopulation diversity and with few haplotypes found at more than one location. Average divergence between species is Average divergence within C. cainii is 0.64% for Cyt b and 1.58% for COI gene region. Average divergence between C. cainii and C. tenuimanus is 12.17% and 5.89% for Cyt b and COI gene regions respectively. The phylogenetic analyses indicated that the two marron species, C. tenuimanus and C. cainii are quite divergent and provide evidence for geographic fragmentation in C. cainii. In C. cainii, the most significant phylogenetic structure was among samples from Western Australia’s south coast river systems compared to the samples from the northern part of the species distribution which showed much less diversity. The study indicates that both the COI and Cyt b gene regions will be valuable for studying geographic population structure within the widespread species, C. cainii.