Genetic population structures of the blue starfish Linckia laevigata and its gastropod ectoparasite Thyca crystallina

Abstract

Comparative analyses of the genetic population structure of hosts and parasites can be useful to elucidate factors that influence dispersal, because common ecological and evolutionary processes can lead to congruent patterns. We studied the comparative genetic population structure based on partial sequences of the mitochondrial cytochrome oxidase I gene of the blue starfish Linckia laevigata and its gastropod ectoparasite Thyca crystallina in order to elucidate evolutionary processes in the Indo-Malay Archipelago. AMOVA revealed a low fixation index but significant genetic population structure (φ ST = 0.03) in L. laevigata, whereas T. crystallina showed panmixing (φ ST = 0.005). According to a hierarchical AMOVA, the populations of L. laevigata could be assigned to the following groups: (1) Eastern Indian Ocean, (2) central Indo-Malay Archipelago and (3) Western Pacific. This pattern of a genetic break in L. laevigata between the Indian and Pacific Ocean, congruent to studies on other marine species in the Indo-Malay Archipelago, is likely due to allopatry caused by Pliocene and Pleistocene glacial sea level low stands.

Return of the ghosts of dispersal past: historical spread and contemporary gene flow in the blue sea star <I>Linckia laevigata</I>

“…The haplotype network highlights the high diversity of haplotypes and presence of many unique or private haplotypes. consistent with previous mtDNA sequencing surveys (i.e., Williams 2000, crandall et al 2008b, Kochzius et al 2009), there were two large emergent clusters. The haplotypes of sampled locations in the West and central Pacific were largely restricted to one cluster (i.e., Vanuatu, New caledonia, tonga and parts of the solomons, Fiji, and Papua New Guinea; top cluster, Fig.…”

“…For mtDNA cOI sequences, Williams et al (2000) described two major clades: an "Indian Ocean" clade, which included both Pacific and Indian Ocean individuals and a "Pacific Ocean" clade that contains only Pacific Ocean individuals with the exception of a few western Australian individuals. crandall et al (2008b) as well as Kochzius et al (2009) sampled comprehensively within the coral triangle and found that the Indian clade haplotypes dominate most Indonesian populations, declining in frequency from Aceh in the west to Jayapura in the east. Within the coral triangle, the greatest population structure was found by grouping Aceh with Krakatau against a cluster of remaining locations, whereas less support was found for a west-east delineation defined by the sunda shelf, and there was modest support for distinctiveness of teluk cenderawasih (crandall et al 2008b).…”

“…Early genetic surveys of L. laevigata were based on allozymes (Williams and benzie 1993, Williams and benzie 1996, Williams et al 2002 or mtDNA (Williams and benzie 1997, Williams et al 2002, crandall et al 2008b, Kochzius et al 2009) and have had broad coverage from the western Pacific to the Indian ocean without much sampling in the coral triangle (e.g., Williams and benzie 1998) or have exclusively focused sampling within the coral triangle (crandall et al 2008b(crandall et al , Kochzius et al 2009). At the broadest scale, support was found for differentiation between the Indian and Pacific oceans based on allozymes, albeit with individuals from Western Australia (Ningaloo) showing greater affinity to western Pacific populations than to western Thailand and south Africa (Williams and benzie 1998, Williams et al 2002, see also Vogler et al 2013 for similar results in crown-of-thorns starfish).…”

“…Within the coral triangle, the greatest population structure was found by grouping Aceh with Krakatau against a cluster of remaining locations, whereas less support was found for a west-east delineation defined by the sunda shelf, and there was modest support for distinctiveness of teluk cenderawasih (crandall et al 2008b). Kochzius et al (2009) suggested that L. laevigata has historically expanded populations into the western Pacific from eastern Indian Ocean origins, a route of colonization running counter to the Indonesian Throughflow (Kochzius et al 2009). …”

Biogeographic origins of the viviparous sea snake assemblage (Elapidae) of the Indian Ocean

“…This scenario is also proposed for few of the reef fishes that do not show genetic divergence/structure across the Indo-Pacific (DiBattista et al, 2012). Further, the 'Coral triangle' in the IAA (Kochzius et al, 2009), Southern Thai-Malay peninsula, and the islands of Java and Sumatra have been shown to be regions of hybridization for many allopatric populations of fish in the IO an WP (Marie et al, 2007;Hobbs et al, 2009;Gaither et al, 2011). Further studies will be needed to identify areas of possible contact and hybridization among the allopatric populations of sea snakes.…”