Very fine-scale population genetic structure of sympatric asterinid sea stars with benthic and pelagic larvae: influence of mating system and dispersal potential

Abstract

The present study investigated the fine‐scale population genetic structure of sympatric asterinid sea stars with contrasting modes of larval development (benthic versus pelagic). Parvulastra exigua lacks a dispersive life phase yet is one of the worlds most widely distributed and abundant sea stars, whereas Meridiastra calcar, a sea star with a dispersive larva, has a more limited regional scale distribution. Populations of P. exigua sampled from tide pools on three adjacent headlands showed significant genetic substructure (mitochodrial DNA control region) at fine spatial scales (tide pools < 300 m apart: FST = 0.249, P < 0.01; headlands 5–15 km apart: FST = 0.125, P = 0.04). As expected, M. calcar populations sampled from the same headlands did not exhibit significant genetic structuring (FST = 0.029, P = 0.14). The life‐history traits of P. exigua, a mixed mating system (selfing + outcrossing), pseudocopulation among closely‐related conspecifics, and an entirely benthic life cycle with a philopatric larva, undoubtedly influence its strong genetic structure across fine spatial scales. Localized genetic structure, especially at the very fine‐scale of tide pools, would not be detected in the more typical regional scale approaches adopted by most studies of marine invertebrate populations. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, ●●, ●●–●●.

Fine‐scale hierarchical genetic structure and kinship analysis of the ascidianPyura chilensisin the southeastern Pacific

“…Life history characteristics influence the genetic structuring of marine invertebrate populations (Barbosa, Klanten, Puritz, Toonen, & Byrne, 2013;Bohonak, 1999;Hart & Marko, 2010;Pelc, Warner, & Gaines, 2009). Many marine invertebrates have a biphasic life cycle composed of a pelagic larval phase and a sessile adult stage (Pusack, Christie, Johnson, Stallings, & Hixon, 2014).…”

“…Variation in larval dispersal and reproductive traits can affect the degree and scale of population genetic structure (Barbosa et al, 2013;Kamel, Hughes, Grosberg, & Stachowicz, 2012). For instance, various studies have shown that the absence (direct development) or the presence of a larval phase (indirect development)…”

Shallow gene pools in the high intertidal: extreme loss of genetic diversity in viviparous sea stars ( Parvulastra )

“…Hermaphroditism and benthic brood protection have evolved in parallel as a suite of life-history traits among multiple asterinid lineages [14], in physiologically extreme high-intertidal habitats and in association with low genetic diversity and strong population differentiation [15]. The apparent ease with which many asterinid lineages can evolve benthic brood protection and self-fertility [20] raises the question of why such lineages have not replaced asterinids with gonochoric outcrossing adults and planktonic larvae? One hypothesis involves the associated high risk of local extirpation and extinction.…”

“…KC866341-42) and two parts of the mitochondrial genome concatenated together as a single locus (several transfer RNA genes plus the control region) [21,22] (KC876801-859). All nine loci are highly variable in other asterinids, including P. exigua [10,19,20]. We used some of the same microsatellite markers to genotype offspring and brooding females from four populations (The Granites, Smooth Pools, Eaglehawk Neck, The Blowhole; table 1) to look for evidence of sexual reproduction and outcrossing.…”

“…Adults (less than or equal to 1 cm diameter) and clutches (less than 100 offspring) are small, and larvae metamorphose into juvenile sea stars in the gonad followed by birth of non-dispersing benthic offspring [14]. This life history probably arose in the common ancestor of these two species in the Pleistocene [18] after their divergence from Parvulastra exigua, in which adults have external fertilization, a mix of selfing and outcrossing, and no brood care [10,19,20]. We found nearly complete loss of genetic diversity in all populations of both live-bearing Parvulastra species (similar to C. hystera), with small population sizes and zero gene flow.…”