Cuizhang Fu

Freshwater fish biodiversity in the Yangtze River basin of China: patterns, threats and conservation

We synthesized information on freshwater fish biodiversity in the Yangtze River basin. We documented 361 species and subspecies that had been recorded and described from the basin. Of these, 177 species are endemic. The basin is usually divided into three parts, i.e. the upper reaches, the middle reaches and the lower reaches. This study indicated that the ‘three reaches’ approach was not supported by fish distribution patterns. Hydrological alterations are perhaps the largest threat to fish biodiversity in the basin. Fishes in the upper reaches will be seriously affected by the construction of the Three Gorges Dam and other dams, and action should be taken for priority conservation. The most immediate restoration need is reconnection of the Yangtze River with its lakes. The cluster of lakes in the Central Yangtze should be protected to maintain habitats for spawning, feeding and migration of migratory fishes. Our study indicates a need to identify areas of high fish biodiversity and to select nature reserves to mitigate the loss of fish biodiversity in the Yangtze River basin.

Genetic diversity of alligator weed in China by RAPD analysis

Random amplified polymorphic DNA (RAPD) was applied to analyze geneticdiversity of an invasive weedy species, alligator weed (Alternantheraphiloxeroides (Martius) Grisebach), collected from eight differentsites in southern China. Amplified by 108 RAPD primers, 391 bands wereidentified from samples collected from three of the eight sites withconsiderably large spatial intervals, but no genetic variation was detectedamong the samples. A total number of 196 RAPD fragments were amplified from allsamples collected in the eight sites by 31 primers that produced the mostconsistent results, but no genetic variation was detected within or betweenpopulations. The molecular data indicated extremely low genetic diversity in thealligator weed. Given the fact that the alligator weed is a serious invasiveweed, and widely found in China, we consider that the low genetic diversity ofthe alligator weed does not affect the success of its expansion in China, andlow genetic diversity does not necessarily lead to endangered status of a plantspecies. In addition, molecular evidence from this study suggests that thealligator weed in southern China might originate from a very few clones or evenonly from a single clone. Therefore, the rapid range expansion of the alligatorweed is most likely the result of a massive vegetative propagation since it wasintroduced in China.

Soil faunal response to land use: effect of estuarine tideland reclamation on nematode communities

Effects of reclaiming estuarine tideland on soil fauna biodiversity were studied in the Yangtze river estuary of China, focusing on nematodes. The responses of the nematode community to the disturbance caused by reclamation can be summarized as: (1) there was no distinct decline in the density of nematodes, but the community structure changed greatly; (2) the proportions of plant feeders and omnivorous nematodes increased after reclamation, whereas the proportions of bacterial feeders and predators decreased; (3) more apparent patchiness of nematode distribution was found in the reclaimed terrestrial environment than in intertidal marshes. Generally, agrocenoses have been characterized by low proportions of predator-omnivores. Our study indicated that omnivorous dorylaimids can be markedly abundant in agroecosystems, depending on the annual crop rotation and tillage practices. The predominant trophic group in cultivated land shifted between omnivorous nematodes and plant feeders, implying that the food chain path changed with agricultural processes. The maturity index (MI) provides little information in the present study, probably because the MI value embraced information of many disturbances including vegetation succession and changes in soil features. The faunal profile, representing both enrichment and structural conditions, is believed to be effective and more informative for analyzing the nematode successional trends.

Phylogenetic position of the enigmatic Lepidogalaxias salamandroides with comment on the orders of lower euteleostean fishes.

This study examines phylogenetic placement of the enigmatic Western Australian Lepidogalaxias, and extends previous studies by including eight new taxa to enable re-examination phylogenetic relationships of lower euteleostean fishes at the ordinal level, based on mitochondrial genomes from 39 ingroup taxa and 17 outgroups. Our results suggest that Lepidogalaxias occupies a basal position among all euteleosts, in contrast with earlier hypotheses that variously suggested a closer relationship to esocid fishes, or to the galaxiid Lovettia. In addition our evidence shows that Osmeriformes should be restricted Retropinnidae, Osmeridae, Plecoglossidae and Salangidae. This reduced Osmeriformes is supported in our results as the sister group of Stomiiformes. Galaxiidae, which is often closely linked to Osmeriformes, emerges as sister group of a combined Osmeriformes, Stomiiformes, Salmoniformes, Esociformes and Argentiformes, and we give Galaxiiformes the rank of order to include all remaining galaxioid fishes (Galaxias and allied taxa, Aplochiton and Lovettia). Our results also support a sister group relationship between Salmoniformes and Esociformes, which are together the sister group of Argentiniformes.

Elevational gradients of diversity for lizards and snakes in the Hengduan Mountains, China

Comparing elevational gradients across a wide spectrum of climatic zones offers an ideal system for testing hypotheses explaining the altitudinal gradients of biodiversity. We document elevational patterns of lizard and snake species richness, and explore how land area and climatic factors may affect species distributions of lizards and snakes. Our synthesis found 42 lizard species and 94 snake species known from the Hengduan Mountains. The lizards are distributed between 500 and 3500 m, and the snakes are distributed between 500 and 4320 m. The relationship between species richness and elevation for lizards and snakes is unimodal. Land area explains a significant amount of the variation in lizard and snake species richness. The cluster analysis reveals pronounced distinct assemblages for lizards and snakes to better reflect the vertical profiles of climate in the mountains. Climatic variables are strongly associated with lizard and snake richness along the elevational gradient. The data strongly implicate water availability as a key constraint on lizard species richness, and annual potential evapotranspiration is the best predictor of snake species richness along the elevational gradient in the Hengduan Mountains.

Biogeographical Consequences of Cenozoic Tectonic Events within East Asian Margins: A Case Study of Hynobius Biogeography

Few studies have explored the role of Cenozoic tectonic evolution in shaping patterns and processes of extant animal distributions within East Asian margins. We select Hynobius salamanders (Amphibia: Hynobiidae) as a model to examine biogeographical consequences of Cenozoic tectonic events within East Asian margins. First, we use GenBank molecular data to reconstruct phylogenetic interrelationships of Hynobius by Bayesian and maximum likelihood analyses. Second, we estimate the divergence time using the Bayesian relaxed clock approach and infer dispersal/vicariance histories under the ‘dispersal–extinction–cladogenesis’ model. Finally, we test whether evolutionary history and biogeographical processes of Hynobius should coincide with the predictions of two major hypotheses (the ‘vicariance’/‘out of southwestern Japan’ hypothesis). The resulting phylogeny confirmed Hynobius as a monophyletic group, which could be divided into nine major clades associated with six geographical areas. Our results show that: (1) the most recent common ancestor of Hynobius was distributed in southwestern Japan and Hokkaido Island, (2) a sister taxon relationship between Hynobius retardatus and all remaining species was the results of a vicariance event between Hokkaido Island and southwestern Japan in the Middle Eocene, (3) ancestral Hynobius in southwestern Japan dispersed into the Taiwan Island, central China, ‘Korean Peninsula and northeastern China’ as well as northeastern Honshu during the Late Eocene–Late Miocene. Our findings suggest that Cenozoic tectonic evolution plays an important role in shaping disjunctive distributions of extant Hynobius within East Asian margins.

Species Delimitation and Historical Biogeography in the Genus Helice (Brachyura: Varunidae) in the Northwestern Pacific

The genus Helice is comprised of four species, H. formosensis, H. latimera, H. tientsinensis, and H. tridens. A recent molecular analysis identified H. formosensis and H. tientsinensis as junior synonyms of H. latimera. We used three mitochondrial and two nuclear genes to further delineate species boundaries in Helice and to add to knowledge of the historical biogeography of the genus. The molecular data revealed deep divergences between the H. formosensis-latimera-tientsinensis complex and H. tridens. Clear genetic separations with incomplete lineage sorting and convincing morphological divergences were detected among H. formosensis, H. latimera, and H. tientsinensis, and a coalescence analysis revealed negligible gene flow among these species, except for weak unidirectional gene flow from H. formosensis to H. latimera. The estimated divergence time of 1.42–1.92 Ma between the H. formosensis-latimera-tientsinensis complex and H. tridens is consistent with the opening of the Tsushima/Korea Strait (1.71–1.52 Ma). The divergence time (∼22-730 ka) among H. formosensis, H. latimera, and H. tientsinensis indicates that the Taiwan Strait acted as a biogeographic barrier during major falls in sea level during the Pleistocene. Our findings indicate that H. formosensis, H. latimera, and H. tientsinensis are valid species, and that straits (Tokara Strait, Tsushima/Korea Strait, and Taiwan Strait), the Okinawa Trough, and currents (Kuroshio Current, Tsushima Current, and Taiwan Strait Warm Current) have acted as geographic barriers resulting in allopatric speciation among onshore marine animals in the northwestern Pacific.

Cryptic Species and Historical Biogeography of Eel Gobies (Gobioidei: Odontamblyopus) Along the Northwestern Pacific Coast

Cryptic species are common in gobioid fishes, as revealed by recent molecular studies. This study collected molecular and morphological data to delimit species boundaries and to reveal the historical biogeography of Odontamblyopus lacepedii sensu lato by sampling 87 specimens from 16 locations in the northwestern Pacific. Phylogenetic trees based on mitochondrial NADH dehydrogenase subunit 5 sequences identified three major clades. Clear morphological separations among these clades were detected by examining morphological characters used in taxonomic diagnosis. Therefore, these clades were delineated as three separate species: O. lacepedii sensu stricto (in the East China Sea, Yellow Sea, Gulf of Bohai, and Ariake Bay); O. sp. (in the southern East China Sea and southern Yellow Sea); and O. rebecca (in the Gulf of Tonkin, northern South China Sea, and southern East China Sea). Estimated divergence times were 0.61 ± 0.15 Ma between O. lacepedii and O. sp., and 2.31±0.36 Ma between O. rebecca and O. lacepedii+O. sp. These findings indicate that isolation of marginal seas and habitat fragmentation during major falls in sea level in the late Pliocene and Pleistocene may have been responsible for genetic breaks among Odontamblyopus species in the northwestern Pacific.

Phylogeographical analysis of an estuarine fish, Salanx ariakensis (Osmeridae: Salanginae) in the north-western Pacific.

This study extended the geographic coverage of a previous study to explore population genetic structure and demographic history in the Ariake icefish Salanx ariakensis from three populations of continental coastlines and one island population in the north-western Pacific based on a partial sequence of the mitochondrial cytochrome b gene. The S. ariakensis showed high genetic diversity and strong genetic structure. Phylogenetic analysis showed a shallow gene tree with no clear phylogeographical structure. Contiguous range expansion and restricted gene flow were inferred to be main population events by nested-clade analysis. Significant genetic differentiations between populations could be attributable to negligible gene flow by coalescent analysis. High nucleotide diversity of each population was due to geographic mixing of heterogenous haplotypes during lowering sea levels of the Pleistocene. These findings indicate that cycles of geographic isolation and secondary contact happened in the Pleistocene glacial-interglacial cycles shaping genetic structure and population demography of S. ariakensis.

Complete mitochondrial genome of a freshwater snail, Semisulcospira libertina (Cerithioidea: Semisulcospiridae)

Abstract The first complete mitochondrial genome (mitogenome) of Cerithioidea (Gastropoda: Caenogastropoda) was determined using a freshwater snail Semisulcospira libertina (Cerithioidea: Semisulcospiridae) as a representative species of the superfamily. The mitogenome was 15,432 bp in length, including 13 typical invertebrate protein-coding genes, 22 transfer RNA genes and 2 ribosomal RNA genes. The overall base composition was 31.4% for A, 17.8% for C, 34.8% for T and 16.0% for G with a A + T bias. The mitogenome of S. libertina displayed novel gene order arrangement compared with published Caenogastropoda mitogenomes to date. This mitogenome contributed in resolving phylogenetic position and interrelationships of Cerithioidea.