no-choice experiments female-choice experiments
Transcrição
no-choice experiments female-choice experiments
Margarida Bárbaro, Mário Mira, Inês Fragata, Pedro Simões, Margarida Lima, Miguel Lopes-Cunha, Bárbara Kellen, Josiane Santos, Margarida Matos and Sara Magalhães Faculdade de Ciências da Universidade de Lisboa, Centro de Biologia Ambiental, Departamento de Biologia Animal, Lisboa, Portugal When a population invades an environment already occupied by conspecifics, the fate of the introgression depends on both differences in relative fitness and reproductive isolation. Here we present a study on the evolution of reproductive barriers of Drosophila subobscura populations, after being introduced to a common laboratorial environment. Will females exhibit a sexual preference for males of their own population? If so, will this preference change during adaptation to the laboratory? Drosophila subobscura individuals were GRO1 collected from the two extremes of the GRO2 GRO3 European latitudinal cline. Populations AD1 AD2 AD3 were three-fold replicated at generation 4 and maintained at 18°C with controlled densities and 12L:12D. Assays of mating behaviour (no-choice and female-choice) were conducted at generations 5, 10 and 17. The traits analyzed for no-choice experiments were frequency of matings (FM), Courtship Latency (CL) and Courtship Duration (CD). As for female-choice experiments, the Isolation Index (I.I.) was estimated which is the ratio of the difference between the frequencies of homogamic and heterogamic matings to the sum of the two. The I.I. is 1 if sexual isolation is complete, 0 if matings are random and negative if Although there were significant differences across generations in the variable CD heterogamic matings outnumber the homogamic ones. (ANCOVA, P<0.05), no trend was observed. At generations 5 and 10, no differences were found between females or males (ANOVA, P>0.05). And at generation 17, NO-CHOICE EXPERIMENTS courtships to Ad females were longer than courtships to Gro females (ANOVA, P<0.05). FEMALE-CHOICE EXPERIMENTS Gro individuals preferred to mate with individuals of the same population (homogamic matings) more than Ad individuals (t-test, P<0.05) at generations 5 and 17, but not at generation 10. Overall, the Isolation Index decreased along generations, but not significantly (Log-linear Analysis of Frequencies, P>0.05). There was a significant increase of FM across generations (ANCOVA, P<0.05). At generation 5 Gro females mated more than Ad females (ANOVA, P<0.05), however there were no differences between males (ANOVA, P>0.05). As for generations 10 and 17, no differences were found between the performances of both males and females (ANOVA, P>0.05). At generations 5 and 17 Gro males mated more than Ad individuals (Log-linear Analysis of Frequencies, P<0.05). Comparing generations 5 and 10, Ad males mated more at generation 10 than at generation 5 (Log-linear Analysis of Frequencies, P<0.05). Gro error bars correspond to the standard errors of the three replicates of each population males increased their number of matings compared to Ad males between generations Overall there was an increase in the number of matings across generations 10 and 17 (Log-linear Analysis of Frequencies, P<0.05). Also, there were significantly (Log-linear, P<0.05). But there were no significant differences across more matings at generation 17 than at generation 10 males (Log-linear, P<0.05). Overall generations in the isolation index. there was an increase in the number of matings across generations (Log-linear Analysis of Frequencies, P<0.05). CL significantly decreased across generations (ANCOVA, P<0.05). At generation 5 Gro • GRO POPULATIONS IN GENERAL WITH BETTER PERFORMANCE THAN AD POPULATIONS males initiated courtship sooner than Ad males (ANOVA, P<0.05). As for generation 10 • MATING PERFORMANCE INCREASED OVER TIME no differences were observed between females or males (ANOVA, P>0.05). And at • ASYMMETRY IN REPRODUCTIVE ISOLATION OBSERVED generation 17 Gro males started courting sooner than Ad males (ANOVA, P<0.05) and • DISASSORTATIVE MATING OF THE SOUTHERN POPULATIONS FADED Gro females were courted sooner than Ad females (ANOVA, P<0.05). AWAY DURING LABORATORY EVOLUTION Acknowledgments This study was partially financed by “Fundação para a Ciência e Tecnologia” (FCT) project nº PTDC/BIA-BEC/098213/2008. M. Mira had a grant from Fundação Amadeu Dias, I.F. has a PhD grant (SFRH/BD/60734/2009), P.S. has a Post-Doc grant and M.C. has a BI grant from FCT. J.S. had a PhD grant (SFRH/BD/28498/2006) and B. K. and M. L. had BTI grants from FCT.