Yexin Yang

Mitochondrial DNA as effective molecular markers for the genetic variation and phylogeny of the family Osteoglossidae

The present study examined the genetic variation of the family Osteoglossidae from different geographical locations based on the mitochondrial NADH dehydrogenase subunit 2 (ND2) and ATPase subunit 6 (ATPase6) genes; we then re-constructed the phylogenetic relationships using the two sequences in combination. The results showed that the partial sequences of mitochondrial ND2 and ATPase6 of the family Osteoglossidae were 813 bp and 669 bp, respectively. A total of 42 species-specific nucleotide positions of the family Osteoglossidae were found to be useful for molecular identification. The sequence variation showed greater differences (8.3%~28.1% for the combined sequences, 8.3%~26.7% for the ND2 gene, and 9.3%~28.7% for the ATPase6 gene) among the different species of Osteoglossidae, and there was a significant association between the genetic difference and geographical location. Phylogenetic analyses using neighbor-joining, Bayesian inference, and maximum parsimony (MP) methods based on the combined sequences of the two genes were able to distinguish the different species and were in agreement with the existing taxonomy based on morphological characters and in association with the geographical distribution among seven species of the family Osteoglossidae.

Nile Tilapia Oreochromis niloticus (L.)

Nile tilapia Oreochromis niloticus (L.) is one of the most widely cultured and most widespread invasive fish species globally. It was the most common alien fish species in South China where it has successfully established populations in the major rivers, and became the dominant species in many sites. The distribution of Nile tilapia in the wild in China is limited by the temperature and the biodiversity of native fish, so it was abundant in the rivers with lower biodiversity in South China. A series of ecological problems may have caused by the increase of Nile tilapia, such as the decrease of the CPUE (catch-per-unit-per-effort) and the income of fishermen, influence on growth of native fish species, increase of the fishing pressure on native species, and decrease of the water transparency and water quality. In order to control the population of the Nile tilapia in the wild, an organophosphate drug called “Mie fei ling” was developed and used. Meanwhile, science popularization has been used to strengthen the understanding of the public and to avoid Nile tilapia to be released and escaped from aquaculture. In order to reduce the ecological impact, more investigations should be conducted and suitable control methods should also be determined for this invasive species.

Spatial variation in adult sex ratio across multiple scales in the invasive golden apple snail, Pomacea canaliculata.

Abstract Adult sex ratio (ASR) has critical effects on behavior and life history and has implications for population demography, including the invasiveness of introduced species. ASR exhibits immense variation in nature, yet the scale dependence of this variation is rarely analyzed. In this study, using the generalized multilevel models, we investigated the variation in ASR across multiple nested spatial scales and analyzed the underlying causes for an invasive species, the golden apple snail Pomacea canaliculata. We partitioned the variance in ASR to describe the variations at different scales and then included the explanatory variables at the individual and group levels to analyze the potential causes driving the variation in ASR. We firstly determined there is a significant female‐biased ASR for this species when accounting for the spatial and temporal autocorrelations of sampling. We found that, counter to nearly equal distributed variation at plot, habitat and region levels, ASR showed little variation at the town level. Temperature and precipitation at the region level were significantly positively associated with ASR, whereas the individual weight, the density characteristic, and sampling time were not significant factors influencing ASR. Our study suggests that offspring sex ratio of this species may shape the general pattern of ASR in the population level while the environmental variables at the region level translate the unbiased offspring sex ratio to the female‐biased ASR. Future research should consider the implications of climate warming on the female‐biased ASR of this invasive species and thus on invasion pattern.

North African Catfish Clarias gariepinus (Burchell)

Fast expansion of aquaculture in China largely relies on the introduction and use of non-native species. However, the introduction and use of non-native species may have negative impacts on local ecosystems and societies. Clarias gariepinus has been widely farmed in China after introduced in 1980 from Africa. However, during aquaculture, this fish species has escaped from farm facilities to the wild. So far, we have little knowledge on the invasion status of this non-native fish in China. In this Chapter, we review the introduction, spread and impacts of C. gariepinus in China, as well as present potential management strategies for this alien fish. Multiple lines of evidence indicate that C. gariepinus has been widely distributed and established population in China and the negative impacts of this alien fish in local ecosystems have been detected. Therefore, we suggest that suitable risk assessment and early waning programs should be well developed to prevent the spread and species-specific fishing tools could be designed to control this alien fish in the wild. We also call for deep investigations on mechanisms of invasions and the technologies of management for C. gariepinus, as well as government and aquaculture industry for proper risk assessment and sound management for sustainable development of aquaculture.

Complete mitochondrial genome of northern spotted barramundi, Scleropages jardinii.

Abstract We sequenced the complete mitogenome of northern spotted barramundi Scleropages jardinii, an ancestral bonytongue with economic and conservation value. The mitogenome is 16,670 bp in length with an A + T content of 52.9%, and contains 13 protein-coding genes, 2rRNAs, 22 tRNAs and a control region. The gene order and arrangement is similar to that of other Osteoglossidae species, as is base composition and codon usage. These data will provide useful molecular information for phylogenetic relationships within the family Osteoglossidae species.