Résumé
The Mediterranean monk seal (Monachus monachus) is one of the world's most endangered marine mammals. Centuries of human persecution along with recent expansion of the fishing industry and intensive shoreline development, have isolated Mediterranean monk seals into small populations in the eastern Mediterranean Basin and eastern North Atlantic. We developed 19 microsatellite loci from the species' genome and investigated genetic patterns within the two existing populations from the North Atlantic (Cabo Blanco and Madeira; N = 50). Microsatellite characterization was conducted on the Cabo Blanco population before the massive die-off that happened in 1997 (N = 30). Four loci deviated from the Hardy-Weinberg equilibrium and six loci showed an excess of homozygotes, suggesting that both nonequilibrium conditions (small-size, bottlenecked population subject to inbreeding) and null alleles are at stake. We could not detect any linkage disequilibrium among locus pairs. The genetic diversity observed in the population was low (mean number of alleles per locus = 2.68) but higher than reported in previous studies using cross-species amplification for the same population. Observed levels of genetic diversity in the post-crash population (N = 16) were slightly lower than in the precrash population (A R = 2.14 vs. 2.39), but the loss of 10 rare alleles in the post-crash population likely reflects the deleterious impact of the 1997 die-off. The Madeiran individuals (N = 4) were fully homozygous (A R = 1.11). Although they were genetically differentiated from Cabo Blanco, allelic distribution showed that Madeira is a genetically depauperate subpopulation of Cabo Blanco, suggesting that translocations from the latter may be considered beneficial. The newly developed microsatellites shall prove useful in managing populations at the individual level, and will be used to further investigate on the genetic structure and historical demography of past and present populations of Mediterranean monk seals.