A genetic comparison of Atlantic and Mediterranean populations of a saltmarsh beetle

Enzyme and dispersal polymorphism in the saltmarsh carabid beetle Pogonus chalceus Marsham were compared between 30 Atlantic and nine Mediterranean European populations. Allozyme results showed that Mediterranean beetles (France, Spain) are genetically distinct from Atlantic populations. All Mediterranean beetles screened showed complete fixation at one locus (IDH1), which in Atlantic populations nearly always varied, whereas some unique Mediterranean alleles were observed for another locus (MPI). Genetic differentiation (allozymes) between Mediterranean populations, although highly significant, appeared to be much lower (F-ST =0.098) than between Atlantic populations (F-ST =0.178). Beetles from the Mediterranean showed a remarkably high dispersal power in all populations studied, whereas Atlantic populations showed wing polymorphism and reduced dispersal power to much more varying degrees. These results, along with relatively lower levels of Pogonus chalceus abundance in many Mediterranean saltmarshes, strongly suggest increased levels of extinction/recolonisation in relation to a lower degree of habitat persistence in Mediterranean compared with most Atlantic saltmarshes. Conclusions are relevant to issues in bath evolutionary and conservation biology. Key welds: population genetics, genetic differentiation, dispersal power, gene flow habitat fragmentation, allozymes, wing polymorphism, saltmarshes, Atlantic, Mediterranean, ground beetles (Carabidae), Pogonus chalceus.