Cryptic invasion and dispersal of an American Daphnia in East Africa

Mergeay, Joachim, Dirk Verschuren, Luc De Meester

Limnol. Oceanogr., 50(4), 2005, 1278-1283 | DOI: 10.4319/lo.2005.50.4.1278

ABSTRACT: We document the cryptic invasion of a North American genotype of Daphnia pulex into Kenya. During a survey of zooplankton samples and dormant egg banks of 41 natural lakes, ponds, and man-made reservoirs throughout central and southern Kenya, D. pulex was found at seven localities in the Rift Valley region. We used DNA sequencing (12S rDNA and cytochrome c oxidase subunit 1 gene [COI]) and microsatellite analyses (10 loci) to characterize each population genetically. A single haplotype was found for both 12S and COI sequences. Comparison with DNA sequences of the D. pulex complex from Europe and America reveals that the Kenyan D. pulex is not closely related to European D. pulex but clusters tightly with the American-Panarctic clade of D. pulex sensu stricto. Microsatellite data further reveal that all seven known Kenyan populations are genetically nearly identical and are dominated by a single clone. All populations except that in Lake Naivasha contained only one multilocus genotype, a fixed heterozygote for 3 of the 10 studied loci. Our data suggest that an obligately parthenogenetic clone of American D. pulex recently immigrated into Kenya and has subsequently dispersed over distances of several hundreds of kilometers. Most likely it was co-introduced accidentally during one of numerous stockings of North American fish or crayfish in Kenya’s Rift Valley lakes since the mid-1920s.

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