Study On Morphological Plasticity And Stability Of Gambusia Affinis

Western Mosquitofish(Gambusia affinis)is a notorious invasive aquatic species native to North America.Biological invasions have received considerable attention in conservation biology as invasive species threaten native species and communities,as well as the structure and function of ecosystems.As we all know,when an invasive species was introduced to a new habitat,where it faces a variety of novel environmental factors that likely act as selection factors promoting phenotypically plastic adaptive changes of various traits(e.g.,morphological,behavioral and physiological),in which morphological differences are the easiest to observe.Due to the close relationship between the structure and function of the organism,different morphological traits will support different adaptability.G.affinis,first introduced to mainland China in the 1920 s,have spread extensively in water bodies in the country nowadays.The widespread distribution of G.affinis points towards a high degree of adaptability and/or phenotypic plasticity.Therefore,the present study investigated the potential geographic and temporal variations in morphological traits of G.affinis,and further explored the source(phenotypic plasticity vs.rapid evolution)of morphological divergence.In this study,I studied morphological variations across populations spanning 17 degrees of latitude and 16 degrees of longitude.And,three populations were sampled for 12 months to study the seasonal changes of the morphological traits.Moreover,I also explored the effects of environmental and genetic factors on the morphological traits of G.affinis by the common garden experiment.The results are as follows:(1)Morphological traits of G.affinis show significant variations along the climatic gradients in China.Males at higher latitudes have larger bodies and larger fat storage areas,while females in inland areas have increased fertility by increasing the abdominal cavity.Males from lower latitudes and more coastal areas possessed wider gonopodia with increased armament.(2)There are significant seasonal variations in body divergences between different regions of G.affinis.Females from higher latitudes possess larger body sizes and larger abdominal cavities in summer(the peak breeding season of G.affinis),and vice versa.(3)According to the common garden experiments,geographic variations in body morphology of G.affinis were mainly caused by phenotypic plasticity,while the differences of the gonopodium were mainly caused by genetic differentiation.In summary,these results indicate sexual selection,as well as natural selection plays an important role in the morphological evolution of invasive species,reveal different reproductive strategies in different environments(e.g.temperature,food resource availability and predation pressure),and uncover the relative contributions of phenotypic plasticity versus rapid evolutionary change in the invasion process.This study provides a theoretical basis for further studies on evolutionary ecology and deepens our understanding of the mechanisms underlying range expansion and colonization of novel environments.