Taking the heat: distinct vulnerability to thermal stress of central and threatened peripheral lineages of a marine macroalga

Abstract

Aim Although many studies have reported the effects of climate change on species' distributions, most of them consider each species as a physiologically homogenous unit. However, different lineages or populations inhabiting distinct bioregions within a species' distributional range can retain unique genetic diversity that could result in distinct adaptive capacities. A recent, large, climate‐correlated distributional range contraction occurred at the southern edge of the intertidal macroalga Fucus vesiculosus, causing loss of genetic diversity unique to the southern clade. We tested for differential selective constraints and signs of local adaptation to thermal stress in the two genetic lineages. Location Iberian Atlantic shores. Methods We performed a series of common garden experiments and a field reciprocal transplant. Results In the laboratory, southern F. vesiculosus showed higher resilience to heat stress than northern individuals. On the southwest coast of Portugal, local individuals grew more than those transplanted from the northern range; in the north of Portugal, growth rates did not differ significantly between lineages. Conclusions We present evidence for unique adaptive traits at the retreating edge of the species' distribution that could be lost if warming trends persist. The loss of the distinct southern genetic heritage could end potential ongoing diversification or speciation processes and impoverishes the adaptive potential of the species as a whole.

Dual influence of terrestrial and marine historical processes on the phylogeography of the Brazilian intertidal red alga Gracilaria caudata

“…, Saada et al. ). Ecotypic divergence has been shown to lead to rapid speciation in several organisms including macroalgae (i.e., adaptation to low salinity in the Baltic sea in Fucus in the time span of a few hundreds of years, Pereyra et al.…”

“…Differences in sensitivity to UVB radiation were also detected between G. birdiae strains from CE and SP states (Ayres-Ostrock and . Physiological divergence between habitats, linked to distinct resilience capacity to temperature fluctuation and emersion (i.e., desiccation) stress, has been shown in other intertidal seaweeds, for example in the brown alga Fucus vesiculosus (Nicastro et al 2013, Saada et al 2016. Ecotypic divergence has been shown to lead to rapid speciation in several organisms including macroalgae (i.e., adaptation to low salinity in the Baltic sea in Fucus in the time span of a few hundreds of years, Pereyra et al 2009).…”

Climate Change Impacts on Seagrass Meadows and Macroalgal Forests: An Integrative Perspective on Acclimation and Adaptation Potential

“…Macrophytes can be locally adapted to their thermal regime (e.g., Zardi et al, 2013;Pereira et al, 2015;Saada et al, 2016;King et al, in press). This means that migrations are rather the dislocation of those adapted subpopulations, and must also be investigated/modeled as such (as in Assis et al, 2016b).…”

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

“…When such approaches were employed variation in thermal phenotype was still observed. In range centre to range edge transplants (cool to warm conditions), which simulate warming scenarios, studies either found that central populations could not tolerate range edge conditions (Gerard andDu Bois 1988, Bennett et al 2015) or performed poorer than local individuals (Saada et al 2016).…”

“…Locations where this threshold was exceeded during the Ningaloo Niño heatwave in 2011 (Feng et al 2013) experienced widespread population loss and shifts in community structure (Smale and Wernberg 2013). Similarly, Saada et al, (2016) concluded that intraspecific differences in thermal tolerances of the intertidal fucoid, Fucus vesiculosus, may render central populations along the Iberian Peninsula vulnerable to warming.…”