Effects of habitat fragmentation on allozyme diversity and conservation status of the coastal sand dune plant Stachys maritima (Lamiaceae) in the Iberian Peninsula

Allozyme electrophoresis was used to evaluate levels and distribution of genetic diversity in Iberian populations of the threatened coastal sand dune plant Stachys maritima (Lamiaceae). During the last century, this species was subjected to severe habitat fragmentation, mainly as a consequence of tourism activities and urban pressures, with a decreasing of area up to 99% in the Iberian Peninsula and a remaining total population size of ca. 250 individuals. Extremely low levels of genetic variation were detected (P = 14.0, A = 1.16 and H-e = 0.066). From the 20 interpretable loci found, only 4 were polymorphic and another one, the ldh-2 locus, showed a fixed heterozygous banding pattern, which may be attributed to gene duplication. Low values of diversity can be related to small population size and isolation of populations. The degree of threat has been increased from vulnerable (VU) to critically endangered (CR), according to the IUCN criteria. Conservation policies should be focused on maintaining population size and gene flow, in addition to preserving its habitat, although reintroductions and reinforcements appear to be necessary to ensure long-term viability of populations.