Genetic Diversity of Daphnia pulex in the Middle and Lower Reaches of the Yangtze River

Abstract

Increased human activities and environmental changes may lead to genetic diversity variations of Cladocerans in water. Daphnia pulex are distributed throughout the world and often regarded as a model organism. The 16S rDNA, cytochrome c oxidase subunit I (COI), and 18S genes were used as molecular marks. The genetic diversity and phylogeny of D. pulex obtained from 10 water bodies in the middle and lower reaches of the Yangtze River were studied. For 16S rDNA, COI gene, and 18S gene, the A+T content (65.4%, 58.4%, and 54.6%) was significantly higher than the G+C content (34.6%, 41.6% and 45.4%). This result was consistent with higher A and T contents among invertebrates. Based on the genetic distances of 16S rDNA and COI genes, the genetic differences of D. pulex from 10 water bodies located in the middle and lower reaches of the Yangtze River in China was minimal (0%–0.8% for 16S rDNA and 0%–1.5% for COI gene). However, D. pulex evolved into two branches in the phylogenetic trees, which coincided with its geographical distribution. Compared with D. pulex from other countries, the average genetic distance of D. pulex obtained from 10 water bodies in the middle and lower reaches of the Yangtze River reached 9.1%–10.5%, thereby indicating that D. pulex may have evolved into different subspecies.

Genetic diversity and differentiation of Daphnia galeata in the middle and lower reaches of the Yangtze River, China

“…Similarly, the genetic differentiation of other Daphnia species from water bodies in the middle and lower reaches of the Yangtze River had been observed at different levels (Wang, Zhang, et al, ; Wei et al, ; Wu, Wang, et al, ). Wei et al () found that three genetically differentiated D. galeata subgroups from eight lakes in the lower reaches of the Yangtze River were observed and did not cluster by their geographical origin in overall.…”

“…Both 16S rDNA and CO I genes are two popular markers in identifying the genetic differentiation and phylogeny of Daphnia species (Ma et al, ; Ma, Petrusek, Wolinska, Hu, & Yin, ; Wang, Zhang, et al, ; Xu et al, , ). In the present study, the A + T contents were all higher than the C + G contents in the 16S rDNA and CO I gene sequences of D. galeata , which was consistent with other Daphnia species (Hebert et al, ; Wang, Zhang, et al, ; Wu, Wang, et al, ; Xu et al, ). Moreover, our results suggested that the combined analysis of the 16S rDNA and CO I gene sequences could clarify more genetic differentiation of D. galeata from water bodies located in the middle and lower reaches of the Yangtze River, China.…”

“…Wei et al () found that three genetically differentiated D. galeata subgroups from eight lakes in the lower reaches of the Yangtze River were observed and did not cluster by their geographical origin in overall. Wang, Zhang, et al () detected that 10 D. pluex populations could initially differentiate into two branches of the middle populations and the lower populations of the Yangtze River. Wu, Wang, et al () discovered that seven D. similoides sinensis populations were obviously clustered two main clades based on the CO I gene sequence, and thought that the habitat fragmentation due to the barrier of the dams and sluices promoted the genetic differentiation and phylogeography of D. similoides sinensis in the middle and lower reaches of the Yangtze River.…”

“…Along the Yangtze River Basin, many tributaries of the river and lakes are distributed, which is an ideal habitat for studying the genetic differentiation of Daphnia . Wang, Zhang, et al () observed the genetic differentiation among D. pulex populations distributed in 10 water regions in the middle and lower reaches of the Yangtze River. Wang () also found genetic differences among Daphnia similoides sinensis from the hatching of resting eggs in different sedimentary layers of Lake Chaohu.…”

“…Wang, Zhang, et al () observed the genetic differentiation among D. pulex populations distributed in 10 water regions in the middle and lower reaches of the Yangtze River. Wang () also found genetic differences among Daphnia similoides sinensis from the hatching of resting eggs in different sedimentary layers of Lake Chaohu. Wu, Wang, et al () found that D. similoides sinensis from seven water bodies located in the middle and lower reaches of the Yangtze River had evolved into two clades, namely the Yangtze River clade and the Huaihe River clade.…”