Genetic diversity and population structure in two species of sea cucumber: differing patterns according to mode of development

Abstract

The population structure of two species of sea cucumber was examined based on mitochondrial DNA sequence analysis. Cucumaria miniata, a species with pelagic nonfeeding larvae lasting less than 2 weeks, and C. pseudocurata, a brooding species lacking a pelagic phase, both occur over similar wide ranges of the northeastern Pacific between Alaska and California. No significant genetic structuring was observed among C. miniata samples with 95% of the observed nucleotide variance attributable to that within population samples. Conversely, only 3.4% of the observed variance was attributed to that within C. pseudocurata population samples, with sampling sites typically greater than 100 km apart. At a finer scale, two C. pseudocurata population samples taken 5 km apart were not statistically different. A significant genetic disjunction was observed among populations of the brooding species, but not in species with pelagic larvae, north of Vancouver Island, Canada, corresponding to the splitting of the California and Alaska currents. Given the observed high levels of genetic diversity in northern samples, this genetic break indicates survival in northern, as well as southern, Pleistocene refugia. These results clearly demonstrate the effects that changes in life‐history patterns can have on dispersal, population structure, and the potential for speciation events.

Spatial pattern of genetic and morphological diversity in the direct developer Acanthina monodon (Gastropoda: Mollusca)

“…Several previous studies on marine species with limited dispersion from different taxonomic groups have found similar patterns (e.g. sea cucumbers: Arndt & Smith 1998;fishes: Riginos & Victor 2001, Dawson et al 2002barnacles: Sotka et al 2004;gastropods: Kyle & Boulding 2000, Collin 2001, Johnson & Black 2006, Lee & Boulding 2009corals: Hellberg 1996, Miller & Ayre 2008, Pelc et al 2009; see also a meta-analysis by Kelly & Palumbi 2010). Nevertheless, the 2 main groups observed in the isolation by distance analysis and the significant grouping pattern detected in the AMOVA and SAMOVA revealed a mesoscale (between region) genetic subdivision, suggesting that factors other than the characteristic life cycle of A. monodon may explain its phylogeographic pattern.…”

Large-scale genetic patchiness among NE Atlantic populations of the brittle star Ophiothrix fragilis

“…Comparative studies of closely related species with contrasting larval lifespans show that the genetic structure of a given species is not necessarily correlated to its dispersal ability. While population connectivity often conforms to what can be expected based on larval lifespan (McMillan et al 1992, Arndt & Smith 1998, Kyle & Boulding 2000, the opposite situation is also encountered. Certain species with a long planktonic phase have a more pronounced genetic structure than species with direct development (Todd et al 1998, Marko 2004, Bowen et al 2006.…”

Genetic diversity and population structure of two South American marine gastropods,Crepipatella dilatataandC. fecunda(Gastropoda: Calyptraeidae): Distinct patterns based on developmental mode

“…As planktonic larvae can remain suspended in the water column at the mercy of ocean currents for weeks or months, it is commonly supposed that benthic species with planktonic larvae have higher levels of dispersal and lower degrees of genetic structuring than species with direct development (Kelly & Palumbi 2010). Comparative studies which have examined the population structure of echinoderms (Arndt & Smith 1998;Iuri et al 2007), bryozoans (Watts & Thorpe *Correspondence: Benjamín E. Guzmán, Departamento de Zoología, Universidad de Concepción, Casilla 160-C, Concepción, Chile. Email: beguzman@ udec.cl 2006), crustaceans (Duffy 1993), corals (Hellberg 1996;Ayre & Hughes 2000), and marine gastropods (Janson 1987;Wilke & Davis 2000;Collin 2001) support the prediction that species with pelagic larvae show low degrees of population structure and genetic differentiation across populations separated by hundreds of kilometres.…”