The effect of lead on fitness components and developmental stability in Drosophila subobscura.

We analyzed the developmental time, egg-to-adult viability, and developmental stability (fluctuating wing size asymmetry) in Drosophila subobscura, maintained for six generations on different concentrations of lead. Development time is significantly affected by generation and lead concentration, but interaction of these factors is not a significant source of variability for this fitness component. Generation and the interaction generation x concentration of lead significantly affect egg-to-adult viability. Levene's test of heterogeneity of variance showed that variability of FA is not significant in any of the samples. Within both lead concentrations females showed significantly higher FA indices for the wing width than males. Within sexes, a significantly higher FA was found only in females for wing width FA between the control and the lower concentration of lead. The results show that if strong relationship between FA and the studied fitness components exists, it results in a stronger selection of unstable genotypes under lead as a stress factor and, consequently, FA needs to be used with caution as a biomarker in natural populations under environmental stress.

Monitoring of the genetic structure of natural populations: change of the effective population size and inversion polymorphism in Drosophila subobscura.

We analyzed changes in the genetic structure and effective population size of two ecologically distinct populations of Drosophila subobscura over several years. Population sizes of D. subobscura in beech and oak wood habitats for a period of 6 years were estimated by the capture-mark-release-recapture method. Inversion polymorphism parameters were also assessed in the same populations for a period of 3 years. Significant differences in the numbers of individuals were observed between sexes. This affected the effective population sizes between particular years. The ratio of the effective size over the cenzus dropped significantly in beech wood in 2 years. Although overall heterozygosity remained unchanged during the years in both habitats, frequencies of gene arrangements on five chromosomes show variability. After the bottleneck, some complex chromosomal arrangements appeared for the first time in both populations. Standard gene arrangements of chromosome A increased in frequency over the years in each habitat, while the complex arrangements remain rather stable and specific for each population. The results obtained indicate that the population structure may significantly change if the effective size of D. subobscura population is reduced, which is mostly related to microclimatic changes in habitats. Based on the results to date, monitoring of microevolutionary changes by using D. subobscura and its relatives seems a promising way to study the effects of global climate changes.