Genetic Diversity And Multiple Paternity Of Atlantic Molly,Poecilia Mexicana

Atlantic molly(Poecilia mexicana)is native to the southern Gulf of Mexico and Guatemala.This species does not migrate and usually inhabits freshwater and slightly salty springs.The habitat of Atlantic molly is unique in that it can both colonize rich hydrogen sulfide and non-hydrogen sulfide springs.Hydrogen sulfide is an acutely respiratory toxicity and it is fatal to most metazoans(including fishes)even the micromolar concentrations.Although there are a wealth of literatures and data on the adaptability of organisms in extreme environments,we still know little about the underlying mechanisms that contribute to the diversity and complexity of reproductive strategies.At first,I speculated that(1)there are differences in genetic diversity between the populations of hydrogen sulfide habitats and non-hydrogen sulfide habitats,and the effects of hydrogen sulfide on adult fish,juvenile fish and eggs are also different between different populations;(2)multiple paternity is common in both hydrogen sulfide and non-hydrogen sulfide populations and the number of sires in hydrogen sulfide population is more than that in non-hydrogen sulfide population.In order to assess the genetic diversity and multiple paternity of Atlantic molly populations in different habitats,this study based on nine highly polymorphic microsatellite markers of five Atlantic molly populations from different habitats in the River Puyacatengo(17°27'5.87''N,92°53'12.87''W)in the southern Gulf of Mexico.The main results of this study are as follows:1.From the results of PCoA,there was genetic differentiation between the five populations of Atlantic molly,although the genetic differentiation was small and the genetic differentiation coefficient of hydrogen sulfide habitats was higher than others.2.From the results of STRUCTURE,there were no differences in the likelihood assignment of females and juveniles,but the eggs'assignment scores were different in the three hybrid populations(puyha,puyhb and puyhc).3.Multiple paternity was common in each populations and female's standard length and fecundity were highly correlated between populations.ANCOVA suggested that number of sires showed no different significance between the populations,while reproductive skew had different significance and the differences mainly came from the fecundity of females.Reproductive skew and fecundity had a positive relationship(R~2=0.140).In summary,this thesis mainly explored the genetic diversity of Atlantic molly in different habitats,and made us understand the reproductive strategies of organisms in extreme environments.All of these provided a foundation for further study on the adaptive evolution of Atlantic molly.