Decadal stability in genetic variation and structure in the intertidal seaweed Fucus serratus (Heterokontophyta: Fucaceae)

Abstract

BackgroundThe spatial distribution of genetic diversity and structure has important implications for conservation as it reveals a species’ strong and weak points with regard to stability and evolutionary capacity. Temporal genetic stability is rarely tested in marine species other than commercially important fishes, but is crucial for the utility of temporal snapshots in conservation management. High and stable diversity can help to mitigate the predicted northward range shift of seaweeds under the impact of climate change. Given the key ecological role of fucoid seaweeds along rocky shores, the positive effect of genetic diversity may reach beyond the species level to stabilize the entire intertidal ecosystem along the temperate North Atlantic. In this study, we estimated the effective population size, as well as temporal changes in genetic structure and diversity of the seaweed F. serratus using 22 microsatellite markers. Samples were taken across latitudes and a range of temperature regimes at seven locations with decadal sampling (2000 and 2010).ResultsAcross latitudes, genetic structure and diversity remained stable over 5–10 generations. Stable small-scale structure enhanced regional diversity throughout the species’ range. In accordance with its biogeographic history, effective population size and diversity peaked in the species’ mid-range in Brittany (France), and declined towards its leading and trailing edge to the north and south. At the species’ southern edge, multi-locus-heterozygosity displayed a strong decline from 1999 to 2010.ConclusionTemporally stable genetic structure over small spatial scales is a potential driver for local adaptation and species radiation in the genus Fucus. Survival and adaptation of the low-diversity leading edge of F. serratus may be enhanced by regional gene flow and ‘surfing’ of favorable mutations or impaired by the accumulation of deleterious mutations. Our results have clear implications for the conservation of F. serratus at its genetically unique southern edge in Northwest Iberia, where increasing temperatures are likely the major cause for the decline not only of F. serratus, but also other intertidal and subtidal macroalgae. We expect that F. serratus will disappear from Northwest Iberia by 2100 if genetic rescue is not induced by the influx of genetic variation from Brittany.Electronic supplementary materialThe online version of this article (10.1186/s12862-018-1213-2) contains supplementary material, which is available to authorized users.

The microbiome of the habitat‐forming brown alga Fucus vesiculosus (Phaeophyceae) has similar cross‐Atlantic structure that reflects past and present drivers1

“…These studies mirror the lottery hypothesis for community assembly of coral reef fishes (Sale 1979) to explain functionally similar but taxonomically different microbial assemblages (Burke et al 2011, Ghaderiardakani et al 2017. However, for latitudinally varying bacterial communities, the core bacteria essential to host function and structural integrity might change at retreating edge distributions if hosts have altered genetic variability that coincides with phylogeographic history and range contractions (Muhlin and Brawley 2009, Neiva et al 2015, Jueterbock et al 2018, Casado-Amez ua et al 2019, Qiu et al 2019, Coleman et al 2020.…”

Genetic tropicalisation following a marine heatwave

“…The few existing temporally replicated seaweed studies show contrasting results. For example, Fucus serratus populations sampled 10 years apart across Europe, showed temporal genetic stability 48 except in warm range edge populations that were thermally stressed. These populations experienced a 90% decline in abundance and greater homozygosity (decline in MLH), possibly as a result of selection favouring thermal tolerance 48 .…”

“…For example, Fucus serratus populations sampled 10 years apart across Europe, showed temporal genetic stability 48 except in warm range edge populations that were thermally stressed. These populations experienced a 90% decline in abundance and greater homozygosity (decline in MLH), possibly as a result of selection favouring thermal tolerance 48 . Conversely, an extreme event (earthquake) in Chile resulted in a decline in Agarophyton chilense genetic diversity (loss of rare alleles) immediately following the event, but recovery occurred after 2 years 72 .…”

“…The total number of alleles or allelic richness (Na) per locus, the observed (Ho) and expected (He) heterozygosity and the number of private alleles (unique to a particular site) were estimated for each population before and after the MHW using GENALEX 6.5 46 and GENETIX 4.05 47 also used to estimate pairwise Weir and Cockerham's F ST . MLH (multi-locus heterozygosity or the mean number of heterozygous loci per individual) was calculated using the R package InbreedR at each site before and after the heatwave as this metric has previously been shown to be a sensitive metric of thermal change 48 . F ST and F IS were computed per population in FSTAT 3.2 49 .…”

Natural history collections recapitulate 200 years of faunal change

“…Both decline and expansion should leave population genetic signatures, i.e. changes in effective population size [75][76][77][78][79][80], which can be inferred from a few specimens [81]. This is certainly an exciting new route to explore the potential of natural history collections.…”