Low genetic variation and isolation of northern peripheral populations of a red seaweed (Grateloupia lanceola)

Abstract

Marine macroalgae are rarely considered from the point of view of conservation and the assessment of their conservation status is often limited by a lack of appropriate data. The red algae Grateloupia lanceola is a common inhabitant of Atlantic rocky shores along West Africa that also occurs in a small number of enclaves in the north-west Iberian Peninsula (NWIP). NWIP populations are notoriously separated from the main range of the species, and were proposed as candidates for inclusion in the regional list of species of conservation concern. In an attempt to provide further information to assess the status of these populations, amplified fragment length polymorphism (AFLP) and mitochondrial cytochrome oxidase subunit 2 and subunit 3 gene (cox2-3) sequences were used to investigate their genetic structure in the Iberian Peninsula. In contrast with the absence of variation in the cox2-3 region, AFLP revealed significant genetic differentiation and a clear isolation by distance pattern for samples separated by 100 s to 1000 km along Iberian shores. Together with assignment/exclusion tests, these results suggest that G. lanceola has geographically restricted dispersal, and indicate that NWIP sites are probably demographically isolated from other conspecifics. Therefore, it would be a mistake, from a conservation perspective, to assume that these populations may be subsidized by arrivals from distant populations located within the main range of the species. On a regional scale, most NWIP sites cluster into a single genetic unit with low genetic variation. Altogether, these results support the listing of NWIP populations of G. lanceola as vulnerable. Copyright © 2011 John Wiley & Sons, Ltd.