[Temporal and Spatial Variation of Nutrients and Chlorophyll a, and Their Relationship in Pengxi River Backwater Area, Three Gorges Reservoir].

In order to explore the temporal and spatial variation of nutrients and chlorophyll a and their relationship in the Three Gorges Reservoir, nutrients and chlorophyll a were monitored chronically and frequently in Gaoyang Lake in Pengxi River in the Three Gorges Reservoir from May 2013 to May 2014. The study showed that the thermal stratification affected the vertical distribution of chlorophyll a and nutrients. The water thermal stratification in Gaoyang Lake occurred in early March and disappeared in the middle of September, and there was no stratification in winter ( November to February of the second year). Chlorophyll a in the surface water increased from 14.92 microg x L(-1) to 183.73 microg x L(-1) and then the chlorophyll a concentration decreased with the increasing depth of the mixing layer ( epilimnion) in the spring of 2014. Furthermore, phosphorus concentration was significantly different among layers when the water stratified and the concentration gradient of TP between the surface and the bottom was (0.18 +/- 0.04) mg x L(-1). When water was not stratified in Gaoyang Lake, the surface, middle and bottom layers had similar concentrations of chlorophyll a and nutrients, respectively. Nitrate N and dissolved phosphorus were the major components of TN and TP, respectively, during the high water level period in Gaoyang Lake with nitrate N accounting for 71.4%-95.4% of TN and dissolved phosphorus 42.7%-94.% of TP, showing that the backwater from the mainstream of Yangtze was the main source of nitrate N and dissolved phosphorus in Gaoyang Lake.

Ancient lakes revisited: from the ecology to the genetics of speciation.

Explosive speciation in ancient lakes has fascinated biologists for centuries and has inspired classical work on the tempo and modes of speciation. Considerable attention has been directed towards the extrinsic forces of speciation--the geological, geographical and ecological peculiarities of ancient lakes. Recently, there has been a resurgence of interest in the intrinsic nature of these radiations, the biological characteristics conducive to speciation. While new species are thought to arise mainly by the gradual enhancement of reproductive isolation among geographically isolated populations, ancient lakes provide little evidence for a predominant role of geography in speciation. Recent phylogenetic work provides strong evidence that multiple colonization waves were followed by parallel intralacustrine radiations that proceeded at relatively rapid rates despite long-term gene flow through hybridization and introgression. Several studies suggest that hybridization itself might act as a key evolutionary mechanism by triggering major genomic reorganization/revolution and enabling the colonization of new ecological niches in ancient lakes. These studies propose that hybridization is not only of little impediment to diversification but could act as an important force in facilitating habitat transitions, promoting postcolonization adaptations and accelerating diversification. Emerging ecological genomic approaches are beginning to shed light on the long-standing evolutionary dilemma of speciation in the face of gene flow. We propose an integrative programme for future studies on speciation in ancient lakes.