GENETIC DIVERSITY AMONG 4 AMBLEMINI SPECIES (BIVALVIA, UNIONIDAE) IN THE CACHE AND WHITE RIVERS, ARKANSAS

Allozymic analysis of 16 loci was utilized to determine the genetic di versity of four species of mussels in the Tribe Amblemini (Amblema pli cata plicata (Say), Plectomerus dombeyanus (Valenciennes), Quadrula pu stulosa (I. Lea), and Q. quadrula (Rafinesque)) in the Cache and White rivers of Arkansas. Mussel populations of both rivers have been subje cted to frequent harvest, and White River populations have been expose d to periodic habitat destruction due to dredging. Ranges of polymorph ism were from 0.572 for A. plicata to 0.360 for Q.. quadrula; heterozy gosity values ranged from 0.049 for P. dombeyanus to 0.144 for Q. pust ulosa. With the exception of low heterozygosity for Q. quadrula, heter ozygosity and polymorphism values were similar to precious studies inv olving Amblemini of other river drainages. Populations were characteri zed by heterozygote deficiencies at all loci. Several determinants of heterozygote deficiency were investigated, with selection and inbreedi ng posed as viable hypotheses. Bottlenecking may be occurring in Q. qu adrula. Although no evidence of genetic decline associated with bottle necking was identified for the other three Amblemini, mussel beds are on the decline in Arkansas, and loss of genetic diversity is detriment al to the temporal stability of populations.