Diurnal variability of gene arrangement frequencies in Drosophila subobscura populations from two habitats

Abstract

The rich inversion polymorphism of chromosomes of Drosophila subobscura varies in association with environmental changes at spatial and temporal level. Due to random factors this might become less regular and this might be the reason that there is little evidence of altitudinal and seasonal, microgeographic and habitat-related variability. The variability of gene arrangement frequencies over daytime period was investigated in populations of D. subobscura from two ecologically different habitats. According to gene arrangement frequencies and inversion polymorphism parameters populations fit into the existing patterns of regional polymorphism. Even though populations display daytime variability for the frequencies of arrangements of chromosomes U and J, the nonsignificant differences in other arrangement frequencies, as well as data obtained from genetic distances between samples from different times of day, rule out the existence of subpopulations distinguished from each other by diurnal activity within two habitats. Some particular arrangement frequencies vary according to temperature and humidity and some changes appear for different karyotypic combinations between beech and oak habitat, which suggests different adaptive advantages and selective mechanisms. Cluster analysis of gene arrangement frequencies indicates some importance of A chromosome arrangements for diurnal activity and show in dependence to other ecological data that internally fixed daily activity rhythm might exists in D. subobscura. Analysis of light temperature and humidity factors in relation to the frequency data obtained indicate a choice of different ecological niche in a temporally structured habitat due to behavioural genetic information.