Inferring Deleterious-Mutation Parameters in Natural Daphnia Populations

Deng and Lynch (1, 2) proposed to characterize deleterious genomic mutations from changes in the mean and genetic variance of fitness traits upon selfing in outcrossing populations. Such observations can be readily acquired in cyclical parthenogens. Selfing and life-table experiments were performed for two such Daphnia populations. A significant inbreeding depression and an increase of genetic variance for all traits analyzed were observed. Deng and Lynch's (2) procedures were employed to estimate the genomic mutation rate (U), mean dominance coefficient ( [Image: see text] ), mean selection coefficient ( [Image: see text] ), and scaled genomic mutational variance ( [Image: see text] ). On average, [Image: see text] , [Image: see text] , [Image: see text] and [Image: see text] (^ indicates an estimate) are 0.84, 0.30, 0.14 and 4.6E-4 respectively. For the true values, the [Image: see text] and [Image: see text] are lower bounds, and [Image: see text] and [Image: see text] upper bounds

Cladocera of Malaysia and Singapore with new records, redescriptions, and remarks on some species

An intensive and extensive sampling of the zooplankton from East and West Malaysia and Singapore yielded 63 cladoceran species of which 26 are recorded for this region for the first time. Redescriptions of a few species are given together with remarks on some others. The records include the first known occurrence of Alonella nana, Chydorus faviformis and Streblocercus pygmaeus in the tropics. The most diverse fauna was found in rice fields and ponds. The species composition is typical for a tropical region and lacks the families Polyphemidae, Leptodoridae and Holopedidae. Also Daphnia was extremely rare