[Coexistence strategies of invaded gobies in the Dianchi Lake, Yunnan, China]. / äº‘å—æ»‡æ± å ¥ä¾µè™¾è™Žé±¼ç±»çš„å ±å­˜ç­–ç•¥.

Gobiids are widespread invasive species, with many species from this group usually invade into the same ecosystem simultaneously. Understanding the mechanisms underlying the coexi-stence of different gobiid species in the sympatric habitats is a key issue in fish invasion ecology. Incorporating morphological analyses, spatial distribution survey, and trophic analyses, we examined the coexistence strategy of Mugilogobius myxodermus and related species (the earlier invaders) in Dianchi Lake, Yunnan, China. Our results showed significant differences in morphology and spatial distribution among the four invasive gobies species (i.e., M. myxodermus, Micropercops swinhonis, Rhinogobius giurinus and Rhinogobius cliffordpopei). The spatial niche index of M. myxodermus was the highest. Food composition between M. myxodermus and other gobies was significantly different, with the former mainly feeding on Chydorus ovalis and Cypris sp. The trophic diversity index of M. myxodermus was the highest. Overall, we found that morphological differences, spatial niche diffe-rentiation, and trophic niche differentiation contributed to the coexistence of the gobies in Dianchi Lake, which could help M. myxodermus reduce interspecific competition. Importantly, the feeding strategy is the key factor determining population size and habitas of M. myxodermus during their competition with the other gobies, and finally contributing to the dominant position in the study area.

Sex dimorphism of Yunnanilus analis and its habitat adaptation in Xingyun Lake, Yunnan, China.

Yunnanilus is a group of endemic fish inhabit in Yun-Gui Plateau and its adjacent areas. They show the characteristic of sex dimorphism, which could be an important reason for their adaptation to karst habitats. Here, we used Yunnanilus analis as the model to understand the sex dimorphism characteristics and its adaptation to the karst habitats. The sex dimorphism, female fecundity, and food specialization of Y. analis were investigated in Xingyun Lake, Jiangchuan, Yunnan. Our results showed that Y. analis exhibit sex size dimorphism (sex dimorphism index=0.23; female with larger body size). There were stains on the transverse sections at females body, but not in males. Males had dark longitudinal lines at their body sides. Morphological differences between males and females were confirmed by the results of one-way analyses of variance (ANOVA), multivariate statistical analyses, principal component analyses, discriminant analyses, and one-way analyses of similarity (ANOSIM) on total length, standard body length, fork length, head width vs. heal length, and the distance between the starting point of ventral fin to the starting point of pectoral fin vs. standard body length. Fecundity of female fish was 1364.5±489.3 (470-2430) eggs, which were positively correlated with their body size. Both female and male Y. analis mainly feed on Chironomid larvae and mayfly naiads. Their food composition was somehow similar, with significantly statistical difference. In conclusion, fecundity selection pressure and food specialization should be the main factors contributing to the evolution of Y. analis' sex dimorphism. More importantly, sex dimorphism of Y. analis is a significant adaptation to the karstic habitats.

[Ecomorphological traits explaining the competition exclusion between Oryzias and mosqui-tofish].

The theory of ecomorphology predicts that species with similar morphological traits can occupy similar ecological niche, which may cause competitive exclusion. To apply this theory into fish invasion ecology research is of significance for understanding the interaction between native and invasive species. Here, we compared the morphological difference between two native (Oryzias pectoralis, Oryzias curvinotus) and one invasive species (Gambusia affinis) to explore the competitive exclusion among them. The results showed that despite O. pectoralis and O. curvinotus were sympa-tric species, they varied in spatial distribution. Such a result supported the theory of ecomorphology, which predicts that two species with similar morphological traits might have strong competition. Moreover, their population density exhibited a significant negative relationship with that of G. affinis. The morphology of G. affinis and both Oryzias species were more similar when comparing to other fish in the assemblage. Results from the cluster analysis showed that G. affinis and Oryzias species were close in a branch, with extremely low spatial niche overlap between invasive mosquitofish and native Oryzias species. There was significant negative correlation between the population abundance of mosquitofish and Oryzias species. All the results suggested that mosquitofish led to population decline of both Oryzias species, due to the ecomorphological similarity. More studies are needed to better understand the mechanisms of G. affinis invasion in habitats of native Oryzias species.