Genetic population structure across a range of geographic scales in the commercially exploited marine gastropod Buccinum undatum

Abstract

Marine invertebrates are exploited increasingly as food resources worldwide, but knowledge of genetic population structure is limited for most commercially valuable taxa. We investigated genetic structure in the widely distributed, subtidal gastropod Buccinum undatum by screening samples from 28 locations at 5 microsatellite loci. Multidimensional scaling and cluster analysis were applied to study macrogeographic structure, and revealed 4 well-supported groupings of populations: Canada, Iceland, Swedish Skaggerak, and a cluster containing most samples from the European continental shelf (hereafter 'Shelf'). A fifth cluster comprising all 5 samples from the Solent (UK) relied on exceptional differentiation of just 2 alleles, which is consistent with significant evidence for recent bottlenecks in this area. Within the Shelf cluster most pairwise tests of differentiation were significant, although the global F ST of 0.014 was very low for a direct-developing species. Our data suggest that use of highly polymorphic markers caused a relatively minor downward bias to F ST , although historical connectivity of populations that are not in migration-drift equilibrium might be more important. However, significant isolation by distance among British North Sea coast samples (F ST = 0.010) is consistent with approach to equilibrium and suggests recent gene flow, probably between semi-continuous populations. At a microgeographic scale, we found migration to be consistently higher from inshore to offshore within 3 separate areas; a factor that may underpin the lower diversity and greater differentiation observed for bay and inlet populations. Such populations might serve as important sources of genetic diversity, but are likely to be particularly vulnerable to exploitation.

Independence of neutral and adaptive divergence in a low dispersal marine mollusc

“…In all cases, these deviations resulted from heterozygote deficiencies. The consistency of observations across sample sites for Bu145 and Bu76 suggests the presence of null alleles as the most probable cause for the departures from Hardy-Weinberg expectations and is consistent with the findings of Weetman et al (2006) for these loci. Following these authors, we used Brookfield's (1996) method ('Brookfield 1' in MICRO-CHECKER) to estimate null allele frequencies (r; Table 3) for Bu145 and Bu76, and generated a dataset that included the null alleles recoded as missing data.…”

“…We found an overall level of spatial population structuring greater than that detected by Weetman et al (2006) among populations distributed along the western, southern and eastern coasts of Britain. The most important genetic breaks (Fig.…”

“…The present genetic data allow for a direct comparison with a recent study conducted using the same marker loci over a broader area of the NE Atlantic (Weetman et al 2006), albeit excluding Irish locations. We found an overall level of spatial population structuring greater than that detected by Weetman et al (2006) among populations distributed along the western, southern and eastern coasts of Britain.…”

“…An extensive population genetic study across the NE Atlantic (Weetman et al 2006) -but not including the Irish shelf -has shown that, while significant levels of genetic structuring in this species can occur locally at spatial scales of tens of km, populations generally seem to have large neighbourhood sizes and are likely to maintain connectivity through a stepping-stone mechanism (Slatkin 1993). Here, we set out to investigate spatial population structure of whelk populations around Ireland, using both neutral genetic markers and phenotypic descriptors, in order to examine the independence or interplay of demographic and adaptive processes in the contemporary evolution of these populations.…”

Genetic population structure of Neptune whelk in northern Japan inferred from microsatellite DNA variation

“…Microsatellites, also known as short tandem repeats, are currently the most powerful set of loci for population genetics, because of the high variability at individual level with biparental inheritance, co-dominance, and the high rate of molecular evolution. msDNA markers have proven useful to estimate the genetic population structure in several gastropods, including a freshwater snail (Meunier et al 2004) and some marine species (Weetman et al 2006). Considering the results of genetic analysis, we discuss the effect of current and recent gene flow and historical factors for population structure of N. arthritica.…”