Abstract:

To understand the phylogeography of the Daphnia longispina complex (consisting of three species: Daphnia longispina, Daphnia galeata and Daphnia dentifera) in the lakes of Tibet, we amplified the mitochondria COI sequences of the Daphnia longispina complex from Tibetan lakes and compared these with sequences from GenBank (containing Daphnia longispina from Europe, Daphnia galeata from the low altitudes area of eastern China, and Daphnia dentifera from Canada). Results showed that there is significant differentiation within Daphnia longispina, Daphnia galeata and Daphnia dentifera in the lakes of Tibet. The genetic diversity within Daphnia dentifera is 0.33-2.32%, 0.33-2.74% for Daphnia galeata, and 1.33-5.50% for Daphnia longispina, representing the largest among the three species. Both Maximum Likelihood and Bayes trees based on mitochondria COI sequences showed that the Daphnia longispina complex was composed of three obvious clades, corresponding to Daphnia longispina, Daphnia galeata and Daphnia dentifera, respectively. The genetic diversity among the clades was 9.40-16.98%, according to a Kimura 2-parameter model. Haplotype network based on the mitochondria COI sequences showed that the Daphnia longispina complex was composed of three branches, corresponding to Daphnia longispina, Daphnia galeata and Daphnia dentifera, respectively. Early Chinese records showed that Daphnia longispina was widely distributed, but in this present study, Daphnia longispina only appeared in Lake Bangongcuo, and Daphnia galeata and Daphnia dentifera were more widely distributed. Because of the difficulty in morphological identification as well as the lack of molecular data in early investigations, the early records of Daphnia longispina in China were probably confused with Daphnia galeata or Daphnia dentifera.

Key words: Daphnia, mitochondrial gene, Tibet, phylogeny