Abstract
Daphnia on the Tibetan Plateau has been little studied, and information on species diversity and biogeography is lacking. Here, we conducted a 4‐year survey using the barcoding fragment of the mitochondrial COI gene to determine the distribution and diversity of Daphnia species found across the Plateau. Our results show that species richness is higher than previously thought, with total described and provisional species number doubling from 5 to 10. Six of the taxonomic units recovered by DNA taxonomy agreed well with morphology, but DNA barcoding distinguished three clades each for the D. longispina (D. galeata, D. dentifera, and D. longispina) and D. pulex (D. pulex, D. cf. tenebrosa, and D. pulicaria) complexes. The sequence divergence between congeneric species varied within a large range, from 9.25% to 30.71%. The endemic D. tibetana was the most common and widespread species, occurring in 12 hyposaline to mesosaline lakes. The lineage of D. longispina is the first confirmed occurrence in west Tibet.
Highlights
| INTRODUCTIONDNA sequencing has generated abundant molecular information, standard dataset platforms, and universal technical rules for modern taxonomic and biogeographical research (Ratnasingham & Hebert, 2007)
DNA barcoding in the present study revealed that Daphnia species diversity on the Tibetan Plateau is much higher than previously thought (Chiang, 1963; Chiang & Chen, 1974; Chiang & Du, 1979; Chiang et al, 1983; Shen & Sung, 1964), doubling the described and provisional species number from 5 (D. magna, D. tibetana, D. pulex, D. similoides, and D. dentifera) to 10
The average interspecific divergence between Daphnia species on the Tibetan Plateau of 25.23% is similar to that reported in Argentina (25.28%, Adamowicz, Hebert, & Marinone, 2004), but significantly higher than values reported from Churchill, Canada (14.1%, Jeffery et al, 2011)
Summary
DNA sequencing has generated abundant molecular information, standard dataset platforms, and universal technical rules for modern taxonomic and biogeographical research (Ratnasingham & Hebert, 2007). The barcoding fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI) is a popular marker used to identify and differentiate closely related species that are very similar in morphology. Previous fragmentary taxonomic studies of Cladocera on the Tibetan Plateau including the genus Daphnia were based solely on morphology (Chiang, 1963; Chiang & Du, 1979; Shen & Sung, 1964). These were updated after several scientific expeditions to the area during the 1970s (Chiang & Chen, 1974; Chiang, Shen, & Gong, 1983). We employed DNA barcoding and DNA taxonomy through analysis of the mitochondrial marker COI to determine species diversity of the Daphnia genus in lakes and ponds on the Tibetan Plateau. Our study will greatly improve our understanding of distribution and species diversity in Cladocera and may have important implications for the conservation of the Tibetan Plateau freshwater fauna
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