Abstract
The global redistribution of biodiversity will intensify in the coming decades of climate change, making projections of species range shifts and of associated genetic losses important components of conservation planning. Highly-structured marine species, notably brown seaweeds, often harbor unique genetic variation at warmer low-latitude rear edges and thus are of particular concern. Here, a combination of Ecological Niche Models (ENMs) and molecular data is used to forecast the potential near-future impacts of climate change for a warm-temperate, canopy forming seaweed, Bifurcaria bifurcata. ENMs for B. bifurcata were developed using marine and terrestrial climatic variables, and its range projected for 2040-50 and 2090-2100 under two greenhouse emission scenarios. Geographical patterns of genetic diversity were assessed by screening 18 populations spawning the entire distribution for two organelle genes and 6 microsatellite markers. The southern limit of B. bifurcata was predicted to shift northwards to central Morocco by the mid-century. By 2090-2100, depending on the emission scenario, it could either retreat further north to western Iberia or be relocated back to Western Sahara. At the opposing margin, B. bifurcata was predicted to expand its range to Scotland or even Norway. Microsatellite diversity and endemism were highest in Morocco, where a unique and very restricted lineage was also identified. Our results imply that B. bifurcata will maintain a relatively broad latitudinal distribution. Although its persistence is not threatened, the predicted extirpation of a unique southern lineage or even the entire Moroccan diversity hotspot will erase a rich evolutionary legacy and shrink global diversity to current (low) European levels. NW Africa and similarly understudied southern regions should receive added attention if expected range changes and diversity loss of warm-temperate species is not to occur unnoticed.
Highlights
Global warming constitutes, together with land-use change and pollution, a major global anthropogenic threat to biodiversity in both marine and terrestrial systems [1,2,3]
The contribution of each environmental predictor to the models was very similar between Multivariate Adaptive Regression Splines (MARS) and Boosted Regression Trees (BRT) (S3 Table)
Only the values obtained with BRT are discussed
Summary
Together with land-use change and pollution, a major global anthropogenic threat to biodiversity in both marine and terrestrial systems [1,2,3]. There is a general concern that, for most species, evolutionary responses (e.g. evolution of climatic niches) will be largely outpaced by the observed rate of climatic change, forcing populations to move, acclimatize or perish when facing these new climatic environments. Range shifts involve regional extirpations and/or colonization of newly suitable areas, often but not restricted to peripheral range edges, as species track their climatic niches [9]. Ecological Niche Models (ENMs) have been increasingly used to forecast such responses to climatic change. ENMs relate distributional and environmental data to determine the environmental factors underlying species distributions, and can be used to project the potential distribution of suitable habitat (as a proxy for species distributions) in future climatic scenarios, including the geographic areas where species may be under higher risk of extirpation and those more likely to provide new suitable habitats for colonization [10,11]
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