Phylogeography of the Christmas Island blue crab,Discoplax celeste(Decapoda: Gecarcinidae) on Christmas Island, Indian Ocean

Abstract

The land crab,Discoplax celeste(Gecarcinidae) is endemic to Christmas Island in the Indian Ocean. Due to a freshwater-dependant life history, in which the megalopae migrate from the ocean up freshwater streams to their adult terrestrial/freshwater habitat,D. celesteinhabits only a few isolated locations on the island. This restricted distribution is one of a number of factors which has previously highlighted the vulnerability of this species to outside threats. A number of anthropogenic factors including the introduction of multiple invasive species and habitat destruction have led to drastic ecosystem change on Christmas Island. The aim of this study was to investigate whether the restricted geographical distributions ofD. celestepopulations contribute to significant genetic structuring across Christmas Island, with an objective to inform future conservation strategies for this species on Christmas Island. Fragments of the mitochondrial cytochrome oxidase I gene and the control region were sequenced from 95 individuals collected from all five locations on Christmas Island known to be inhabited byD. celeste. Analyses using analysis of molecular variance revealed no evidence of population sub-structuring, indicating that despite any geographical isolation, there is a single population ofD. celesteon Christmas Island. This lack of population differentiation is probably explained by the oceanic dispersal of larvae, rather than terrestrial migration ofD. celeste. Therefore, based on these results, for conservation purposes,D. celesteon Christmas Island can be considered a single management unit.

Mitochondrial DNA Variation Reveals a Sharp Genetic Break within the Distribution of the Blue Land Crab Cardisoma guanhumi in the Western Central Atlantic

“…The CR of the mt DNA has proved to be a useful tool to address evolutionary questions, e.g. the intra-specific population structure of many crab species [17,29,30,31,32,33,34].…”

Population genetics of the fiddler crab Uca sindensis (Alcock, 1900) (Crustacea: Brachyura: Ocypodidae) from the Arabian Sea

“…Even a species with a restricted distribution like U. boninensis (known only from the Ogasawara (= Bonin) Islands, Japan) has a high nucleotide diversity (3.18%, Shih et al 2013a). The pattern is not always easy to decipher; some species with a low diversity like D. celeste (1.0%, Turner et al 2013), has a small range and is endemic to Christmas Island in the Indian Ocean, while E. versicolor (0.7%, Supmee et al 2012) (studied along the Andaman Sea Coast of Thailand) has a wide Southeast Asian distribution. The highly variable CR marker may therefore provide another line of evidence to better understand the genetic structure and molecular diversity at the population and species level.…”

“…Most phylogenetic and phylogeographic studies of marine crabs use the mitochondrial 16S rRNA and cytochrome oxidase subunit I (COI) genetic markers (e.g., Levinton et al 1996;Sturmbauer et al 1996;Shih and Suzuki 2008;Shih et al 2009Shih et al , 2010Shih et al , 2012Davie et al 2010;Wong et al 2010Wong et al , 2011Wong et al , 2012. In addition, the mitochondrial control region marker, with highly variable and fast divergence rates (Avise 2000), has also recently been used for phylogeographic studies of crabs, e.g., Portunus trituberculatus (Miers, 1876) (Portunidae) (Cho et al 2009;Guo et al 2012), U. crassipes (Aoki and Wada 2013), Uca boninensis (Ocypodidae) (Shih et al 2013a), Grapsus grapsus (Linnaeus, 1758) (Grapsidae) (Ströher et al 2011), Episesarma versicolor (Tweedie, 1940) (Sesarmidae) (Supmee et al 2012), Ucides cordatus (Linnaeus, 1763) (Oliveira-Neto et al 2007) (Ucididae), Cardisoma guanhumi (Latreille, in Latreille, Le Peletier, Serville & Guérin, 1828, and Discoplax celeste Ng and Davie, 2012 (Gecarcinidae) (Turner et al 2013).…”