COARSE-GRAINED POPULATION-STRUCTURE IN CENTRAL-EUROPEAN SCULPIN (COTTUS-GOBIO L) - SECONDARY CONTACT OR ONGOING GENETIC DRIFT

Population genetic affinities of 261 European sculpins Cottus gobio L. across the Rhenanian-Danubian and the Rhenanian-Rhonian watersheds we re assessed by horizontal agarose-gel electrophoresis of up to 20 allo zyme systems (encoded by 29 genetic loci). Polymorphism P-mean = 0.068 9 (range: 0.00-0.1379), and heterozygosity H-e(mean) = 0.0167 (range: 0.000-0.0507) indicated low genetic variability within local stocks fr om single streams. Significant genetic distances D-mean = 0.1917 +/- 0 .0336 (D-max = 0.2407), based on differential fixation at 3-6 loci (Ac p-1* Pgdh**, Fh**, Est-1**, Gpi-2**, and Pgm-1**) distinguished popul ations from the Neckar catchment basin from those of the Hochhrein-Obe rrhein and Danube basins. Differential fixation of alleles and pronoun ced genetic distances also separated sculpins of the Rhonian tributary Doubs from Neckarian populations (D-mean = 0.2131 +/- 0.0033; Ah*, A cp-1*, Fh**), of the Doubs from the Danube (D-mean = 0.2177 +/- 0.002 8; Gpi-2*, Pgm-1**, Pgdh**, Ah**), and of the Doubs from the Hochrhei n-Oberrhein (D-mean = 0.1780; Pgm-1*, Pgdh**, Ah**), Genetic distance s between streams within these drainages proved low (Neckar: D-mean = 0.0047 +/- 0.0014, Danube: D-mean = 0.026 +/- 0.0179, Rhine: D-mean = 0.0308). Screening of another 16 small-size samples consisting of 55 s culpins for nine diagnostic loci (Aat-2*, Acp-1**, Acp-2**, Ah**, Est -1*, Fh**, Gpi-2**, Pgdh** and Pgm-1**) confirmed the genetic homogen eity of sculpins within the Danubian and Neckarian drainage systems, b ut Neckarian sculpins were similar to those from the river Main. Popul ations from Hochrhein-Oberrhein resembled the Danubian stock but conta ined a decreasing frequency of 'Neckarian' markers when approaching th e Danubian region. The genetic divergence between Neckarian, Danubian and Rhonian sculpins suggests the existence of hitherto neglected taxa of anteglacial divergence.