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

Enzyme and dispersal polymorphism in the saltmarsh carabid beetle Pogonus c halceus Marsham were compared between 30 Atlantic and nine Mediterranean Eu ropean populations. Allozyme results showed that Mediterranean beetles (Fra nce, Spain) are genetically distinct from Atlantic populations. All Mediter ranean beetles screened showed complete fixation at one locus (IDH1), which in Atlantic populations nearly always varied, whereas some unique Mediterr anean alleles were observed for another locus (MPI). Genetic differentiatio n (allozymes) between Mediterranean populations, although highly significan t, appeared to be much lower (F-ST =0.098) than between Atlantic population s (F-ST =0.178). Beetles from the Mediterranean showed a remarkably high di spersal power in all populations studied, whereas Atlantic populations show ed wing polymorphism and reduced dispersal power to much more varying degre es. These results, along with relatively lower levels of Pogonus chalceus a bundance in many Mediterranean saltmarshes, strongly suggest increased leve ls of extinction/recolonisation in relation to a lower degree of habitat pe rsistence in Mediterranean compared with most Atlantic saltmarshes. Conclus ions are relevant to issues in bath evolutionary and conservation biology. Key welds: population genetics, genetic differentiation, dispersal power, g ene flow habitat fragmentation, allozymes, wing polymorphism, saltmarshes, Atlantic, Mediterranean, ground beetles (Carabidae), Pogonus chalceus.