Shift happens: trailing edge contraction associated with recent warming trends threatens a distinct genetic lineage in the marine macroalga Fucus vesiculosus

Abstract

BackgroundSignificant effects of recent global climate change have already been observed in a variety of ecosystems, with evidence for shifts in species ranges, but rarely have such consequences been related to the changes in the species genetic pool. The stretch of Atlantic coast between North Africa and North Iberia is ideal for studying the relationship between species distribution and climate change as it includes the distributional limits of a considerable number of both cold- and warm-water species.We compared temporal changes in distribution of the canopy-forming alga Fucus vesiculosus with historical sea surface temperature (SST) patterns to draw links between range shifts and contemporary climate change. Moreover, we genetically characterized with microsatellite markers previously sampled extinct and extant populations in order to estimate resulting cryptic genetic erosion.ResultsOver the past 30 years, a geographic contraction of the southern range edge of this species has occurred, with a northward latitudinal shift of approximately 1,250 km. Additionally, a more restricted distributional decline was recorded in the Bay of Biscay. Coastal SST warming data over the last three decades revealed a significant increase in temperature along most of the studied coastline, averaging 0.214°C/decade. Importantly, the analysis of existing and extinct population samples clearly distinguished two genetically different groups, a northern and a southern clade. Because of the range contraction, the southern group is currently represented by very few extant populations. This southern edge range shift is thus causing the loss of a distinct component of the species genetic background.ConclusionsWe reveal a climate-correlated diversity loss below the species level, a process that could render the species more vulnerable to future environmental changes and affect its evolutionary potential. This is a remarkable case of genetic uniqueness of a vanishing cryptic genetic clade (southern clade).

Closer to the rear edge: ecology and genetic diversity down the core‐edge gradient of a marine macroalga

“…Four annual environmental predictors were selected based on the biological significance to Fucus spp. along this stretch of coast (e.g., Nicastro et al 2013, Assis et al 2014) and averaged across the years: SST of the hottest and coldest month and air temperature of the hottest and coldest month.…”

Long-term herbarium data reveal the decline of a temperate-water algae at its southern range

“…Tanaka et al, 2012;Smale and Wernberg, 2013;Nicastro et al, 2013). Ocean warming is considered a key factor in the ongoing decline of fucoid species (Martínez et al, 2012).…”

The importance of phenotypic plasticity and local adaptation in driving intraspecific variability in thermal niches of marine macrophytes

“…Unlike many marine species that have large dispersal capacities, marine macrophytes generally exhibit restrictive dispersal with seaweed spores settling within a few metres of the parent alga (Dayton 1985, Schiel and Foster 1986, Santelices 1990, Kendrick and Walker 1991, 1995, Norton 1992 and seagrass pollen and seed dispersal often limited to the meadow in which the adult plant inhabits (Zipperle et al 2011, Kendrick et al 2012. This often results in highly structured distributions (Valero et al 2011, Nicastro et al 2013, Robuchon et al 2014, Assis et al 2015, Neiva et al 2015 and means local ecotypes may be a common characteristic (Gerard and Du Bois 1988) in marine macrophytes, with any associated population decline unable to be ameliorated by migration (Bennett et al 2015, Assis et al 2017, Molinos et al 2017). However, it should be noted that even within this group some species exhibit larger scale dispersal capacities that can result in a closer tracking of habitat as niches shift (Duarte et al 2013).…”

“…Perhaps the most notable is a ~ 1250 km range contraction of the intertidal fucoid, Fucus vesiculosus, from Morocco polewards to the mid Iberian Peninsula over a 30 yr period (Nicastro et al 2013). Many marine macrophytes are foundation species that provide habitat and resources for other species and structure entire communities and ecosystems (Steneck et al 2002, Teagle et al 2017.…”