Host‐targeted RAD‐Seq reveals genetic changes in the coral Oculina patagonica associated with range expansion along the Spanish Mediterranean coast

Abstract

Many organisms are expanding their ranges in response to changing environmental conditions. Understanding the patterns of genetic diversity and adaptation along an expansion front is crucial to assessing a species' long-term success. While next-generation sequencing techniques can reveal these changes in fine detail, ascribing them to a particular species can be difficult for organisms that live in close association with symbionts. Using a novel modified restriction site-associated DNA sequencing (RAD-Seq) protocol to target coral DNA, we collected 595 coral-specific single nucleotide polymorphisms from 189 colonies of the invasive coral Oculina patagonica from the Spanish Mediterranean coast, including established core populations and two expansion fronts. Surprisingly, populations from the recent northern expansion are genetically distinct from the westward expansion and core populations and also harbour greater genetic diversity. We found that temperature may have driven adaptation along the northern expansion, as genome scans for selection found three candidate loci associated with temperature in the north but none in the west. We found no genomic signature of selection associated with artificial substrate, which has been proposed for explaining the rapid spread of O. patagonica. This suggests that this coral is simply an opportunistic colonizer of free space made available by coastal habitat modifications. Our results suggest that unique genetic variation, possibly due to limited dispersal across the Ibiza Channel, an influx of individuals from different depths and/or adaptation to cooler temperatures along the northern expansion front may have facilitated the northward range expansion of O. patagonica in the western Mediterranean.

Is the central‐marginal hypothesis a general rule? Evidence from three distributions of an expanding mangrove species, Avicennia germinans (L.) L

“…USA mangroves also provide three natural replicates of core to margin distribution ranges. Comparing variation across multiple distributions of the same species can provide greater insights into the processes shaping genetic change (Griffin & Willi, ; Kennedy et al, ; Leydet, Grupstra, Coma, Ribes, & Hellberg, ; Micheletti & Storfer, ). For instance, West Florida (WFL) and East Florida (EFL) exhibited a similar decline in neutral genetic diversity, with reductions in mean allelic richness of almost 50% from south to north, and greatest intersite differentiation at the northern range margins, consistent with latitudinal reductions in mangrove abundances along these coastlines (Osland, Feher, et al, ).…”

“…USA mangroves also provide three natural replicates of core to margin distribution ranges. Comparing variation across multiple distributions of the same species can provide greater insights into the processes shaping genetic change (Griffin & Willi, 2014;Kennedy et al, 2017;Leydet, Grupstra, Coma, Ribes, & Hellberg, 2018;Micheletti & Storfer, 2015). For instance, West Florida (WFL) and…”

Signatures of selection in a recent invasion reveals adaptive divergence in a highly vagile invasive species

“…To identify a reduced set of variables that explained environmental variation across the introduced range, we conducted a principle components analysis (PCA) including all environmental variables and run in R using the PRCOMP function (RCoreTeam, 2015) . We calculated the pairwise distance between points on a plot of PC1 and PC2 to calculate pairwise environmental distances between collection localities, which were subsequently used in the analysis of isolation by environment (Leydet et al, 2018, Wang et al, 2013.…”

“…Evidence may be taken from the functional nature of a polymorphism e.g. (Dudaniec et al, 2018, Leydet et al, 2018, however this is still only circumstantial. White et al (2013) recognise this problem and propose replicated SNP analysis across different sections of the invasive range, suggesting that similar clines across multiple regions are less likely to be due to random processes such as drift (White et al, 2013).…”

From Pavement to Population Genomics: Characterizing a Long-Established Non-native Ant in North America Through Citizen Science and ddRADseq

“…Population genomic approaches, in particular, restriction siteassociated DNA sequencing (RADseq) (Miller et al, 2007;Baird et al, 2008;Peterson et al, 2012), offer a cost-effective solution for surveying genome-wide single nucleotide polymorphism (SNPs) in species without a sequenced genome. These techniques have proven useful to understanding species' invasion histories (Dupuis et al, 2018;Leydet et al, 2018;Bors et al, 2019;Cohen and Privman, 2019) and as a non-destructive method for identification and monitoring (reviewed in Taylor and Gemmell, 2016). More generally, emergence of RAD-based techniques have led to wide adoption of these methods in ecological and evolutionary studies of insects (Bagley et al, 2017;Storer et al, 2017;Lower et al, 2018;Zhang et al, 2018;De Jesús-Bonilla et al, 2019), including ants (Moreau and Wray, 2017;Boyle et al, 2018;Avril et al, 2019;Smith et al, 2019), which rank among the most damaging and difficult to control invasive species (Rabitsch, 2011).…”