Long-term annual (1990–2010) monitoring data were analyzed to test the responses of phytoplankton biomass in three lakes in the Yungui Plateau, China, to increasing temperature and increasing nutrient concentrations. The three studied lakes (Lake Fuxian, Lake Erhai and Lake Dianchi) all exhibited significant increases in algal biomass from 1990 to 2010, with increases of 0.111 µg/L, 0.662 µg/L and 3.07 µg/L per year, respectively. The study also indicated that the relative influences of warming and nutrient concentrations on chlorophyll a concentration varied among the lakes and was dependent on trophic level and phytoplankton composition. In Lake Fuxian, the increase in algal biomass was correlated with the rapid growth ofMougeotiaspp., and the total phosphorous concentration was the key factor driving this increase in algal biomass. In Lake Erhai, the dominant species shifted fromDolichospermumspp. toMicrocystisspp. Additionally, the increase in algal biomass in Lake Erhai (involving mainly an increase inMicrocystisspp.) was significantly associated with an increase in total nitrogen (TN) concentration. In Lake Dianchi, warming and increases in TN concentration were the strongest predictors of biomass change.

The geological structure and history of mountains often cause highly complex patterns of evolution. The origin and diversity of the genus Triplophysa is considered to be closely associated with the rapid and persistent rise of the Qinghai-Tibet Plateau (QTP). Species of the genus are widely distributed in the QTP and adjacent regions, and are strongly adapted to its extreme environments. However, the Central Chinese Mountains (CCM), which are far apart from the QTP, also have many Triplophysa populations and yet their taxonomy, phylogeny and origin are unknown. We used three mitochondrial genes of 266 individuals from 29 sites in the CCM to shed light on the evolution of these Triplophysa populations. Phylogenetic analyses and species delimitation revealed seven distinct molecular operational taxonomic units (mOTUs) in the CCM, each with low genetic diversity. Molecular clock and biogeographic analyses suggested that vicariance events resulting from the rapid uplifting of the Qinling and Taihang Mountains initialized diversification in the Pliocene. During the early Pleistocene, dispersal events in the central parts of the Yellow River drainage altered genetic diversity and led to the currently observed biogeographic patterns. Our results suggest the presence of at least six species of Triplophysa in the CCM and more are likely to be discovered in the future.

Background: An important aspect of studying evolution is to understand how new species are formed and their uniqueness is maintained. Hybridization can lead to the formation of new species through reorganization of the adaptive system and significant changes in phenotype. Interestingly, eight stable strains of 2nNCRC derived from interspecies hybridization have been established in our laboratory. To examine the phylogeographical pattern of the widely distributed genusCarassiusacross Eurasia and investigate the possible homoploid hybrid origin of theCarassius auratuscomplex lineage in light of past climatic events, the mitochondrial genome (mtDNA) and one nuclear DNA were used to reconstruct the phylogenetic relationship between theC. auratuscomplex and 2nNCRC and to assess how demographic history, dispersal and barriers to gene flow have led to the current distribution of theC. auratuscomplex.Results: As expected, 2nNCRC had a very close relationship with theC. auratuscomplex and similar morphological characteristics to those of theC. auratuscomplex, which is genetically distinct from the other three species ofCarassius. The estimation of divergence time and ancestral state demonstrated that theC. auratuscomplex possibly originated from the Yangtze River basin in China. There were seven sublineages of theC. auratuscomplex across Eurasia and at least four mtDNA lineages endemic to particular geographical regions in China. The primary colonization route from China to Mongolia and the Far East (Russia) occurred during the Late Pliocene, and the diversification of other sublineages of theC. auratuscomplex specifically coincided with the interglacial stage during the Early and Mid-Pleistocene in China.Conclusion: Our results support the origin of theC. auratuscomplex in China, and its wide distribution across Eurasia was mainly due to natural Pleistocene dispersal and recent anthropogenic translocation. The sympatric distribution of the ancestral area for both parents of 2nNCRC and theC. auratuscomplex, as well as the significant changes in the structure of pharyngeal teeth and morphological characteristics between 2nNCRC and its parents, imply that homoploid hybrid speciation (HHS) forC. auratuscould likely have occurred in nature. The diversification pattern indicated an independent evolutionary history of theC. auratuscomplex, which was not separated from the most recent common ancestor ofC. carassiusorC. cuvieri. Considering that the paleoclimate oscillation and the development of an eastward-flowing drainage system during the Pliocene and Pleistocene in China provided an opportunity for hybridization between divergent lineages, the formation of 2nNCRC in our laboratory could be a good candidate for explaining the HHS ofC. auratusin nature.

Species diversity is determined by both local environmental conditions that control differentiation and extinction and the outcome of large-scale processes that affect migration. The latter primarily comprises climatic change and dynamic landscape alteration. In the past few million years, both Southeast Asia and Eastern Africa experienced drastic climatic and geological oscillations: in Southeast Asia, especially in China, the Tibetan Plateau significantly rose up, and the flow of the Yangtze River was reversed. In East Africa, lakes and rivers experienced frequent range expansions and regressions due to the African mega-droughts. To test how such climatic and geological histories of both regions relate to their respective regional species and genetic diversity, a large scale comparative phylogeographic study is essential. Bellamya, a species rich freshwater snail genus that is widely distributed across China and East Africa, represents a suitable model system to address this question. We sequenced mitochondrial and nuclear DNA for members of the genus from China and used published sequences from Africa and some other locations in Asia to investigate their phylogeny and distribution of genetic diversity. Our phylogenetic analysis revealed two monophyletic groups, one in China and one in East Africa. Within the Chinese group, Bellamya species show little genetic differentiation. In contrast, we observe fairly deep divergence among the East African lakes with almost every lake possessing its unique clade. Our results show that strong divergence does not necessarily depend on intrinsic characteristics of a species, but rather is related to the landscape dynamics of a region. Our phylogenetic results suggest that the Bellamya in China and East Africa are independent phylogenetic clades with different evolutionary trajectories. The different climate and geological histories likely contributed to the diverging evolutionary patterns. Repeated range expansions and regressions of lakes likely contributed to the great divergence of Bellamya in East Africa, while reversal of the river courses and intermingling of different lineages had an opposite effect on Bellamya diversification in China.