Fine-scale temperature-associated genetic structure between inshore and offshore populations of sea scallop (Placopecten magellanicus)

Abstract

In the northwest Atlantic Ocean, sea scallop (Placopecten magellanicus) has been characterized by a latitudinal genetic cline with a breakpoint between northern and southern genetic clusters occurring at ~45°N along eastern Nova Scotia, Canada. Using 96 diagnostic single-nucleotide polymorphisms (SNPs) capable of discriminating between northern and southern clusters, we examined fine-scale genetic structure of scallops among 27 sample locations, spanning the largest geographic range evaluated in this species to date (~37-51°N). Here, we confirmed previous observations of northern and southern groups, but we show that the boundary between northern and southern clusters is not a discrete latitudinal break. Instead, at latitudes near the previously described boundary, we found unexpected patterns of fine-scale genetic structure occurring between inshore and offshore sites. Scallops from offshore sites, including St. Pierre Bank and the eastern Scotian Shelf, clustered with southern stocks, whereas inshore sites at similar latitudes clustered with northern stocks. Our analyses revealed significant genetic divergence across small spatial scales (i.e., 129-221 km distances), and that spatial structure over large and fine scales was strongly associated with temperature during seasonal periods of thermal minima. Clear temperature differences between inshore and offshore locations may explain the fine-scale structuring observed, such as why southern lineages of scallop occur at higher latitudes in deeper, warmer offshore waters. Our study supports growing evidence that fine-scale population structure in marine species is common, often environmentally associated, and that consideration of environmental and genomic data can significantly enhance the identification of marine diversity and management units.

Diversity Patterns of Bermuda Grass along Latitudinal Gradients at Different Temperatures in Southeastern China

“…Low temperatures limit the distribution and development of most plant species [ 13 ]. For example, southern lineages of scallops located at higher latitudes live in warmer offshore waters because they have adapted to high temperatures [ 46 ]. Genetic variation should allow populations of A. millepora to adapt to gradual warming, while novel genetic mutations could induce further adaptations [ 47 ].…”

RAD sequencing sheds new light on the genetic structure and local adaptation of European scallops and resolves their demographic histories

“…Despite the expectation that local adaptation should be stronger in species with restricted gene flow 45 , there is a growing consensus that selection can also shape the genetic composition of species with highly dispersive planktonic larvae 17 . In particular, studies of several benthic organisms including the sea scallop P. magellanicus have identified ambient temperature as a key selective pressure influencing fine-scale genetic structure 19 . To build upon these studies, we therefore conducted gradient forest analysis to identify the most important explanatory environmental variables, and then sought to characterize candidate environmentally associated loci as those markers identified by both LFMM and BayPass.…”

“…Broadly, there is a large body of evidence suggesting that local adaptation to temperature is a pervasive phenomenon across marine invertebrates 17 . More specifically, a related scallop species ( Placopecten magellanicus ) in North America was found to exhibit geographical variation in thermal tolerance 18 as well as significant genetic associations with sea surface temperature (SST), implying an important role of ecologically mediated divergence 19 . In European scallops, growth performance correlates positively with SST 20 and proteomic differences have also been observed between scallops from different latitudes 21 , although it is not known if these differences have a mainly genetic or plastic basis.…”

Fine‐scale seascape genomics of an exploited marine species, the common cockle Cerastoderma edule, using a multimodelling approach

“…The spatial environmental association analysis identified several environmental factors that appeared associated with the population structure observed at neutral and outlier genetic markers. This is a strong statistical approach, which has already been successfully employed to study the influence of the environment on the genetic structure of commercially important bivalves, such as the eastern oyster (Crassostrea virginica; Bernatchez et al, 2019) and Atlantic deep-sea scallop (Placopecten magellanicus; Lehnert et al, 2019).…”