Spatial and temporal population genetic structure of four northeastern Pacific littorinid gastropods: the effect of mode of larval development on variation at one mitochondrial and two nuclear DNA markers

Abstract

We investigated the effect of development mode on the spatial and temporal population genetic structure of four littorinid gastropod species. Snails were collected from the same three sites on the west coast of Vancouver Island, Canada in 1997 and again in 2007. DNA sequences were obtained for one mitochondrial gene, cytochrome b (Cyt b), and for up to two nuclear genes, heat shock cognate 70 (HSC70) and aminopeptidase N intron (APN54). We found that the mean level of genetic diversity and long-term effective population sizes (N(e)) were significantly greater for two species, Littorina scutulata and L. plena, that had a planktotrophic larval stage than for two species, Littorina sitkana and L. subrotundata, that laid benthic egg masses which hatched directly into crawl-away juveniles. Predictably, two poorly dispersing species, L. sitkana and L. subrotundata, showed significant spatial genetic structure at an 11- to 65-km geographical scale that was not observed in the two planktotrophic species. Conversely, the two planktotrophic species had more temporal genetic structure over a 10-year interval than did the two direct-developing species and showed highly significant temporal structure for spatially pooled samples. The greater temporal genetic variation of the two planktotrophic species may have been caused by their high fecundity, high larval dispersal, and low but spatially correlated early survivorship. The sweepstakes-like reproductive success of the planktotrophic species could allow a few related females to populate hundreds of kilometres of coastline and may explain their substantially larger temporal genetic variance but lower spatial genetic variance relative to the direct-developing species.

Genetic variation and population structure of the Pacific oyster Crassostrea gigas in the northwestern Pacific inferred from mitochondrial COI sequences

“…The coastal currents are composed of the China coastal current (CCC) from the SCS, the Subei coastal current (SBCC) and Lubei coastal current (LBCC), all of which are characterized by low salinity flow into the ECS/YS [22]. Theoretically, oceanic currents operating during the pelagic phase should facilitate larvae dispersal and promote genetic exchange [25]. Another important factor is the CDW, which carries huge freshwater outflow into the ECS and profoundly influences the hydrological and ecological features of the ECS [26].…”

Highly Connected Populations and Temporal Stability in Allelic Frequencies of a Harvested Crab from the Southern Pacific Coast

“…For example, temporal variations in allele frequencies have been described [14,15] and related to a phenomenon called chaotic patchiness [16,17]. Several hypotheses try to explain the factors that can cause genetic heterogeneity, for example strong genetic drift caused by high mortality during early development, the action of natural selection during the larval stage and catastrophic events in the marine environment could change the pattern of larval recruitment in different years [18]. The possibility of low larvae mixture [19] and high reproductive variance [20] may also occur.…”

Phylogeography in Nassarius mud snails: Complex patterns in congeneric species

“…Some species showed a high level of gene flow at large geographical scales [3, 4, 6, 10], whereas others had complex biogeographical patterns such as unstructured genetic heterogeneity at fine geographical scales [12, 13]. Such difference is mainly explained by complex interactions of unique hydrological characteristics and several biological features, such as direct versus indirect development models [13, 14], and/or the presence of lecithotrophic versus planktotrophic larvae [13–15]. For instance, a comprehensive study in 50 marine species on the Pacific coast of North America showed clear difference in the population genetic structure between species with and without pelagic development [16].…”

“…The passive dispersal at larval stages via marine currents is the major, and often the only, natural dispersal means for gene flow among populations, particularly at large geographical scales [10–16]. Consequently, planktonic larvae advected by marine currents play a significant role in the formation of phylogeographical and population genetic patterns in coastal sessile gastropods [12–16], and relatively direct evidence can be obtained by testing the interplays between planktonic larvae and marine currents based on coastal sessile gastropods, such as species with versus without planktonic larval phases [13]. As biological characteristics play crucial roles in interactions among multiple factors such as hydrological features, sister species with the same or similar biological characteristics represent promising models to test how these factors interplay to shape phylogeographical patterns.…”