The federally endangered Duskytail Darter, Etheostoma percnurum Jenkins, is known from only six highly disjunct populations in the Tennessee and Cumberland river drainages of Kentucky, Tennessee, and Virginia. Only four are extant. Variation in morphology including meristics, morphometrics, and pigmentation was examined among the four extant populations and limited specimens from the two extirpated populations (Abrams Creek and South Fork Holston River). Analyses of these data found each of the extant populations is morphologically diagnosable. The few specimens avail- able from Abrams Creek and South Fork Holston River prevented thorough assessment of variation, and these were grouped with their closest geographic counterparts, Citico Creek, and Little River, respectively. Three new morphologi- cally diagnosable species are described: E. sitikuense, the Citico Darter, from Citico Creek, Abrams Creek, and Tellico River (Tennessee River system); E. marmorpinnum, the Marbled Darter, from the Little River and South Fork Holston River (Tennessee River system); and E. lemniscatum, the Tuxedo Darter, from the Big South Fork (Cumberland River system). Each species warrants federal protection as an endangered species.
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Genetic and demographic modeling of two endangered mussel species, Epioblasma brevidens and E. capsaeformis, in the Clinch River, U.S.A., was conducted to determine quantitative criteria to evaluate performance of extant and reintroduced populations. Reintroduction modelling indicated that the initial population size created during a 5 year build-up phase greatly affected final population size at 25 years, being similar to the population size at the end of the build-up phase, especially when population growth rate was low. Excluding age 0 individuals, age 1 juveniles or recruits on average comprised approximately 11% and 15% of a stable population of each species, respectively. Age-class distribution of a stable or growing population was characterized by multiple cohorts, including juvenile recruits, sub-adults, and adults. Because of current barriers to dispersal and the low dispersal capability of some mussel species, reintroductions will play a prominent role in restoring populations in the United States.
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