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Shift happens: trailing edge contraction associated with recent warming trends threatens a distinct genetic lineage in the marine macroalga Fucus vesiculosus
Publication . Nicastro, Katy R; I Zardi, Gerardo; Teixeira, Sara; Neiva, J.; Serrão, Ester; Pearson, G. A.
Significant 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. Results Over 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. Conclusions We 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).
Taking the heat: distinct vulnerability to thermal stress of central and threatened peripheral lineages of a marine macroalga
Publication . Saada, Gabriel; Nicastro, Katy R; Jacinto, Rita; McQuaid, Christopher D.; Serrão, Ester; Pearson, G. A.; Zardi, Gerardo I.
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.

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Funding agency

Fundação para a Ciência e a Tecnologia

Funding programme

3599-PPCDT

Funding Award Number

PTDC/MAR/110251/2009

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