GENIC SIMILARITY OF AMERICAN AND EUROPEAN SPECIES OF THE LOBSTERHOMARUS

Abstract

Average amounts of electrophoretically detectable genic variability in European and American lobster populations appear to be similar. More than one allele was detected at 20% of the 41 loci studied; the average number of alleles detected per locus is 1.2 and average proportion of loci heterozygous per individual is 4.0%. While much less genically variable than other invertebrates, Homarus is not atypical when compared with 11 decapod species that average 5.8% heterozygosity. This is consistent with hypotheses relating genetic variability to adaptive strategy. At 30 loci H. gammarus is monomorphic for the common H. americanus allele. Two acid phosphatase systems are fixed or nearly fixed for alternative alleles in the 2 spp. while the remaining polymorphic loci show various degrees of interspecific divergence. Unique H. gammarus alleles were detected at 5 loci but only contribute significantly to species differences at the Acph-5, Me and Pgi-4 loci. Acph-1, Est-2, Pgi-3 and Pgm-1 are polymorphic for the same alleles in both species with various differences in allelic frequencies. Average genetic identity and average genetic distance are I = 0.896 and D = 0.110. Compared to values for conspecific population comparisons, I = 0.994 and D = 0.006, a small but significant amount of genetic divergence separates the European and American lobster. The 2 spp. may have been isolated during the Pleistocene. The apparent weakness of reproductive isolating barriers suggests that these populations have evolved allopatrically and that species hybridization is a potentially important breeding practice in lobster aquaculture.