Dekui He

Molecular phylogeny of the specialized schizothoracine fishes (Teleostei: Cyprinidae), with their implications for the uplift of the Qinghai-Tibetan Plateau

Molecular phylogeny of three genera containing nine species and subspecies of the specialized schizothoracine fishes are investigated based on the complete nucleotide sequence of mitochondrial cytochromeb gene. Meantime relationships between the main cladogenetic events of the specialized schizothoracine fishes and the stepwise uplift of the Qinghai-Tibetan Plateau are also conducted using the molecular clock, which is calibrated by geological isolated events between the upper reaches of the Yellow River and the Qinghai Lake. Results indicated that the specialized schizothoracine fishes are not a monophyly. Five species and subspecies ofPtychobarbus form a monophyly. But three species ofGymnodiptychus do not form a monophyly.Gd. integrigymnatus is a sister taxon of the highly specialized schizothoracine fishes whileGd. pachycheilus has a close relation withGd. dybowskii, and both of them are as a sister group ofDiptychus maculatus. The specialized schizothoracines fishes might have originated during the Miocene (about 10 MaBP), and then the divergence of three genera happened during late Miocene (about 8 MaBP). Their main specialization occurred during the late Pliocene and Pleistocene (3.54-0.42 MaBP). The main cladogenetic events of the specialized schizothoracine fishes are mostly correlated with the geological tectonic events and intensive climate shift happened at 8, 3.6, 2.5 and 1.7 MaBP of the late Cenozoic. Molecular clock data do not support the hypothesis that the Qinghai-Tibetan Plateau uplifted to near present or even higher elevations during the Oligocene or Miocene, and neither in agreement with the view that the plateau uplifting reached only to an altitude of 2000 m during the late Pliocene (about 2.6 MaBP).

Otolith characteristics and age determination of an endemic Ptychobarbus dipogon (Regan, 1905) (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo River, Tibet

We describe the microincrements, checks and annuli in the lapilli of the schizothoracine Ptychobarbus dipogon, an endemic species of the Tibetan plateau. We collected samples in the Yarlung Tsangpo River and its tributaries on a monthly basis (from April 2004 to August 2006). We describe the shape features of the three pairs of otoliths and document the full trajectory of lapillus development. We found that five to seven checks were clearly visible in the opaque zone of the first annulus. The pattern of 21–23 daily growth increments within each check might be explained as a lunar-induced deposition. We counted between 137 and 154 increments within the first annulus. Annuli appeared as a sequence of gradually declining increment widths, whereas false rings were characterized by abrupt checks. Our oldest estimates were 23+years for males and 44+ for females. The time of annulus completion was clearly between March and April each year using monthly marginal increments analysis. We consider the factors responsible for daily increment formation as an endogenous circadian rhythm. Environmental information, such as strong sunlight and cold water temperatures in the Tibetan Plateau, could reinforce the endogenous daily cycle. Our results provided important data addressing the ecology and population dynamics of P. dipogon.

Phylogeography of Schizothorax o’connori (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo River, Tibet

Schizothorax o’connori is endemic to the Yarlung Tsangpo River on the Tibetan Plateau. We assessed the relative impacts of historical and contemporary factors in organizing genetic variation in S. o’connori populations using mitochondrial cytochrome b sequences. We analyzed 191 samples from 11 populations and identified 78 haplotypes. The phylogenetic analyses and analysis of molecular variance all supported the same conclusions of two well-differentiated east–west phylogroups, separated by the Tsangpo Great Gorge. The split between the two clades accounted for 58% of the genetic variance observed among the examined samples. Waterfalls as effective barriers played an important role in shaping the phylogeographical structure of this species. Analyses of migration rates revealed that upstream dispersal was limited crossing waterfalls. Our study revealed substantial spatial and temporal variation in the influence of landscape features on contemporary patterns of genetic structure in S. o’connori. Interglacial range expansions clearly left their mark on contemporary populations above the Tsangpo Great Gorge.

Comparative phylogeography and evolutionary history of schizothoracine fishes in the Changtang Plateau and their implications for the lake level and Pleistocene climate fluctuations

Abstract The water level oscillation of endorheic lakes and extent change of glaciers associated with the Asian monsoon are known as prominent representatives of climatic and environmental events in the Tibetan Plateau during the Quaternary. However, details process in spatial and temporal changes are still debated. We use the schizothoracines as a palaeoclimatic proxy to test two hypotheses concerning the evolution of Quaternary glaciations and lakes of the Changtang Plateau: (1) the Tibetan glaciations generally tended to decrease since the middle Pleistocene; (2) the lakes expansion was driven by summer monsoon rainfall. Based on a wide range‐wide sampling throughout in the Changtang Plateau and its adjacent drainages, we constructed phylogeny and demographic histories of schizothoracines in the Changtang Plateau. Our results showed that the populations of the exorheic rivers and lakes in southern Tibet possessed higher genetic variability, earlier coalescent and expansion times than those of the endorheic lakes in the Changtang Plateau. Population expansions are highly consistent with phases of strong summer monsoon and high lake level during interglacial stages. The maximum growth rate intervals showed three pulses from 64.7 to 54.8, 39.6 to 31.0, and 14.9 to 2.4 kya respectively. The significant positive correlations were found between regional precipitation and genetic diversity, as well as coalescence time of populations in the endorheic lakes. We suggested that the demographic history of the schizothoracines reflects the spatial and temporal changes in climate and lake level, in particular, in regional precipitation gradients associated with changes of the South Asian monsoon, and supports the climatic hypothesis of a general diminishing tend in Tibetan glaciations in the Tibetan Plateau since the middle Pleistocene.

Phenotypic Shifts in Life History Traits Influence Invasion Success of Goldfish in the Yarlung Tsangpo River, Tibet

Goldfish Carassius auratus have been established in myriad ecosystems outside of their native ranges, and part of their successful establishment in new ecosystems might be attributed to the shift in life history traits. To explore the role of phenotypic shifts in Goldfish invasions, we quantified and compared spawning times and growth rates in the early life history of nonnative Goldfish from Chabalang and Chongdui wetlands in the Yarlung Tsangpo River basin. Spawning of nonnative Goldfish began on March 20 and April 14 for the Chabalang and the Chongdui populations, respectively, and both were considerably earlier than native populations despite the cold environments in the Yarlung Tsangpo River basin. Growth rates for the Chabalang population were significantly higher than those for the Chongdui population during the first 14 d posthatch; however, growth rates for the Chongdui population became higher after the 37th day. Within the Chabalang population, Goldfish hatching later had faster growth rates than individuals hatching earlier. Consequently, it seems that shifts in the timing of spawning and growth rates play an important role in the invasion success of Goldfish in extremely cold climates.

Relationships between climate and growth of Gymnocypris selincuoensis in the Tibetan Plateau

The consequences of climate change are becoming increasingly evident in the Tibetan Plateau, represented by glaciers retreating and lakes expanding, but the biological response to climate change by plateau–lake ecosystems is poorly known. In this study, we applied dendrochronology methods to develop a growth index chronology with otolith increment widths of Selincuo naked carp (Gymnocypris selincuoensis), which is an endemic species in Lake Selincuo (4530 m), and investigated the relationships between fish growth and climate variables (regional and global) in the last three decades. A correlation analysis and principle component regression analysis between regional climate factors and the growth index chronology indicated that the growth of G. selincuoensis was significantly and positively correlated with length of the growing season and temperature-related variables, particularly during the growing season. Most of global climate variables, which are relevant to the Asian monsoon and the midlatitude westerlies, such as El Nino Southern Oscillation Index, the Arctic Oscillation, North Atlantic Oscillation, and North America Pattern, showed negative but not significant correlations with the annual growth of Selincuo naked carp. This may have resulted from the high elevation of the Tibetan Plateau and the high mountains surrounding this area. In comparison, the Pacific Decade Oscillation (PDO) negatively affected the growth of G. selincuoensis. The reason maybe that enhancement of the PDO can lead to cold conditions in this area. Taken together, the results indicate that the Tibetan Plateau fish has been affected by global climate change, particularly during the growing season, and global climate change likely has important effects on productivity of aquatic ecosystems in this area.

The reproductive strategies of an endemic Tibetan fish, Gymnocypris selincuoensis

ABSTRACT The reproductive traits of Gymnocypris selincuoensis from Selincuo Lake and its tributaries were investigated in 1997 and 1998. The youngest mature male was age 7 with a standard length (SL) of 172.0 mm, and the youngest mature female was age 8 with a SL of 194.0 mm. The L50s of SL and age at first maturity were respectively 250.32 mm and age 9 for males and 224.71 mm and age 8 for females. The gonadosomatic index (GSI) significantly changed with seasons for mature individuals but not for immature individuals. GSIs of mature females at stages IV and V of ovary development increased with SL and reached a maximum value at the SL range from 370 mm to 390 mm; the GSIs of mature males were negatively correlated with SL. The breeding season lasted from early April to early August. Egg size did not significantly change with SL but increased with the delay of spawning. The individual absolute fecundity varied from 1,341 to 28,002 eggs (mean 12,607±7,349), and the individual relative fecundity varied from 6.4 to 42.0 eggs.g−1 (mean 25.5±9.7). The individual fecundity increased with total body weight; it also increased with SL for those of SL less than 370 mm. There was a rest of spawning for mature individuals.

The complete mitochondrial genome organization of Schizothorax Plagiostomus (Teleostei: Cyprinidae) from Northern Pakistan

Abstract Schizothorax plagiostomus, a fresh water fish, is an economically important fish of Pakistan. In this study, the complete mitochondrial DNA (mtDNA) sequence of S. plagiostomus was explored. The mitogenome length was found to be 16 563bp with 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and 2 non-coding regions: origin of light-strand replication (OL) and control region (D-loop). All genes were encoded on the heavy strand except ND6 and few tRNA genes. The overall base composition of S. plagiostomus of the heavy strand was T 25.5%, C 27.0%, A 29.8% and G 17.8%, A + T content 55.3% and G + C content 44.7%. The phylogenetic tree suggests that S. esocinus, S. progastus, S. richardsonii and S. plagiostomus may have closer affinities than other fish of the genus Schizothorax. This mitogenome sequence would be useful for phylogenetic analysis and conservation of this species in Pakistan.

Trends and potential cautions in food web research from a bibliometric analysis

Understanding food webs is important and useful for planning environmental conservation, management and restoration. However, research on food webs is not uniform globally; it tends to be concentrated in specific areas or ecosystem types, and would hinder our understanding of food webs and ecosystem processes. This study examined the trends in food web research over the past decades by analysing publication data from Web of Science; in particular, it focused on the ecosystem types studied, countries in which the studies were done, and which countries collaborated on the studies. A total of 20,239 publications were examined. The results showed that research on food webs has dramatically increased since the 1990s. Most publications related focused on aquatic ecosystems. North American and European countries contributed much more in terms of research productivity than those from Africa and South America. Collaboration among individual authors and countries has become increasingly intensive. The USA and Canada were consistently the top two productive countries, and had the most frequent collaborations. Our study indicates that food webs from ecosystems other than aquatic ones, such as terrestrial ecosystems, also require more attention in the future; in particular those that exist within countries from Africa and South America.

The complete mitochondrial genome of Rhynchocypris oxycephalus (Cypriniformes: Cyprinidae)

Abstract The Rhynchocypris oxycephalus (Cypriniformes: Cyprinidae) is an ecological important fish in East Asia. In this study, we firstly sequenced the complete mitochondrial genome of R. oxycephalus. The mitogenome is 16,606 bp in length, including 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and two non-coding regions (origin of light–strand replication and control region). The gene content and order is in accord with the common vertebrate form. The nucleotide base composition of H-strand is 28.4% A, 27.2% T, 26.4% C and 18.0% G. The complete mitochondrial genome data would be useful for further studies of genetics, conservation biology and adaptive evolution of R. oxycephalus.