Evolutionary dynamics of molecular markers during local adaptation: a case study in Drosophila subobscura.
BACKGROUND
Natural selection and genetic drift are major forces responsible for temporal genetic changes in populations. Furthermore, these evolutionary forces may interact with each other. Here we study the impact of an ongoing adaptive process at the molecular genetic level by analyzing the temporal genetic changes throughout 40 generations of adaptation to a common laboratory environment. Specifically, genetic variability, population differentiation and demographic structure were compared in two replicated groups of Drosophila subobscura populations recently sampled from different wild sources.


RESULTS
We found evidence for a decline in genetic variability through time, along with an increase in genetic differentiation between all populations studied. The observed decline in genetic variability was higher during the first 14 generations of laboratory adaptation. The two groups of replicated populations showed overall similarity in variability patterns. Our results also revealed changing demographic structure of the populations during laboratory evolution, with lower effective population sizes in the early phase of the adaptive process. One of the ten microsatellites analyzed showed a clearly distinct temporal pattern of allele frequency change, suggesting the occurrence of positive selection affecting the region around that particular locus.


CONCLUSIONS
Genetic drift was responsible for most of the divergence and loss of variability between and within replicates, with most changes occurring during the first generations of laboratory adaptation. We also found evidence suggesting a selective sweep, despite the low number of molecular markers analyzed. Overall, there was a similarity of evolutionary dynamics at the molecular level in our laboratory populations, despite distinct genetic backgrounds and some differences in phenotypic evolution.
Simões
Pedro
P
Universidade de Lisboa, Faculdade de Ciências da Universidade de Lisboa, Centro de Biologia Ambiental, Departamento de Biologia Animal, Campo Grande, 1749-016 Lisboa, Portuga. pmsimoes@fc.ul.pt
Pascual
Marta
M
Santos
Josiane
J
Rose
Michael R
MR
Matos
Margarida
M
D000222:Adaptation, Physiological; D000704:Analysis of Variance; D000818:Animals; D004330:Drosophila / Q000235:genetics*; D040961:Genetic Drift; D005819:Genetic Markers; D014644:Genetic Variation; D006579:Heterozygote; D018895:Microsatellite Repeats; D011156:Population Density; D012641:Selection, Genetic
D005819:Genetic Markers