| Western mosquito fish(Gambusia affinis),native to North America is one of the top 100 invasive species in the world,and in recent years has posed a serious threat to native species in invasive sites through predation and ecological niche competition,causing great harm to local watershed ecosystems.Salinity,as an environmental factor in water bodies,has an important influence on phenotypes and population characteristics of aquatic organisms.In recent years,Global warming and sea level rise have led to an increase in salinity in part of freshwater bodies along with changes in water ecosystems of some regions.Many studies have shown that salinity has a limiting effect on the invasion and dispersal of mosquito fish,and there are great differences in population density,sex ratio and other population characteristics of individuals living in different salinities.However,there is insufficient evidence to explain the cause of this phenomenon,and the ecological mechanism of salinity affecting the invasion of mosquito fish has not been thoroughly studied yet.As phenotypic plasticity mediated by energy investment trade-offs plays an important role in adaptation to the environment(especially for behavioral and life-history traits),it is hypothesized that the effect of salinity on the population characteristics and distribution of mosquito fish may be related to their behavioral and life-history plasticity.Therefore,we used western mosquito fish in Hangzhou as the material,using linear models and other analytical methods,to test the effect of salinity(0‰,10‰,20‰)on their personality traits(boldness,activity,sociability),mating preference(body size)and lifehistory(reproductive biology)traits under laboratory conditions,and further discussed the relationship between them and ecological significance.This study obtained the following main results:(1)Individuals of western mosquito fish showed a general consistency of personality traits across time;salinity had significant effects on the personality traits of both male and female,the boldness of both sexes was significantly reduced in the two salinity treatment groups of 10‰ and 20‰.In addition,male activity,sociability and female activity decreased significantly at a salinity of 20‰,while salinity had no significant effect on female sociability;both male and female individuals exhibited behavioral syndromes,with salinity leading to a synergistic decrease in male activity and sociability,and female boldness and activity.(2)Males in all three treatment groups showed no significant preference on mate size,while female individuals in control and 10‰ salinity treatment groups showed a significant preference for larger males;Salinity had significant effects on the total preference strength of male fish,but no significant effect on female individuals.High salinity led to a decrease in the total preference strength of male fish,implying a decrease in mating desire of males.(3)Salinity had significant effects on the reproductive biology traits of both male and female western mosquito fish.For males,fat content was significantly reduced at 20‰ salinity,while gonadosomatic index was significantly increased in both 10‰ and 20‰ salinity treatment groups;somatic lean weight of unpregnant female was significantly lower in the 10‰salinity treatment group than in the control group;fat content of pregnant females was significantly increased in the 10 ‰ salinity treatment group,while their reproductive allocation and fecundity decreased significantly in the 10‰ and 20‰ salinity treatment groups.These results suggest that salinity changes the energy trade-offs between reproductive biology traits in male and female individuals.In the face of salinity pressure,male tend to maintain investment of reproductive,while female tend to maintain their own survival.(4)The path analysis results indicate that the effects of salinity on the behavioral indicators and reproductive biology traits of male and female western mosquito fish are relatively independent,and no indirect effect of salinity was detected;correlations between behavioral indicators and reproductive biology traits were only found in pregnant females,individuals with life history strategies which tend to invest more energy to growing and sustaining themselves are less brave and more social.In summary,the results of this study indicate that salinity has a comprehensive effect on the behavior(personality traits,mate preference)and life-history(reproductive biology)traits of western mosquito fish.The plastic changes of these phenotypes revealed the trade-off strategies of mosquito fish in response to salinity stress in reproduction,energy investment,and a range of survival-related behaviors.To some extent,this study explains the reasons for the differences in the characteristics of mosquito fish populations under different salinities,and provides new ideas for a deeper understanding of the adaptive mechanism of mosquito fish in the process of invading waters with different salinities,which can help to improve the prevention and control measures of mosquito fish. |
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