Seasonal changes in recombination characteristics in a natural population of Drosophila melanogaster.

Environmental seasonality is a potent evolutionary force, capable of maintaining polymorphism, promoting phenotypic plasticity and causing bet-hedging. In Drosophila, environmental seasonality has been reported to affect life-history traits, tolerance to abiotic stressors and immunity. Oscillations in frequencies of alleles underlying fitness-related traits were also documented alongside SNPs across the genome.

Desiccation-induced changes in recombination rate and crossover interference in Drosophila melanogaster: evidence for fitness-dependent plasticity.

Meiotic recombination is evolutionarily ambiguous, as being associated with both benefits and costs to its bearers, with the resultant dependent on a variety of conditions. While existing theoretical models explain the emergence and maintenance of recombination, some of its essential features remain underexplored. Here we focus on one such feature, recombination plasticity, and test whether recombination response to stress is fitness-dependent.

Genomic divergence and adaptive convergence in from Evolution Canyon, Israel.

Biodiversity refugia formed by unique features of the Mediterranean arid landscape, such as the dramatic ecological contrast of "Evolution Canyon," provide a natural laboratory in which local adaptations to divergent microclimate conditions can be investigated. Significant insights have been provided by studies of diversifying along the thermal gradient in Evolution Canyon, but a comparative framework to survey adaptive convergence across sister species at the site has been lacking. To fill this void, we present an analysis of genomic polymorphism and evolutionary divergence of , a close relative of with which it co-occurs on both slopes of the canyon.

Regulation of gene expression and RNA editing in Drosophila adapting to divergent microclimates.

Determining the mechanisms by which a species adapts to its environment is a key endeavor in the study of evolution. In particular, relatively little is known about how transcriptional processes are fine-tuned to adjust to different environmental conditions. Here we study Drosophila melanogaster from 'Evolution Canyon' in Israel, which consists of two opposing slopes with divergent microclimates.

Rapid genomic changes in Drosophila melanogaster adapting to desiccation stress in an experimental evolution system.

Background: Experimental evolution studies, coupled with whole genome resequencing and advances in bioinformatics, have become a powerful tool for exploring how populations respond to selection at the genome-wide level, complementary to genome-wide association studies (GWASs) and linkage mapping experiments as strategies to connect genotype and phenotype. In this experiment, we analyzed genomes of Drosophila melanogaster from lines evolving under long-term directional selection for increased desiccation resistance in comparison with control (no-selection) lines.

Results: We demonstrate that adaptive responses to desiccation stress have exerted extensive footprints on the genomes, manifested through a high degree of fixation of alleles in surrounding neighborhoods of eroded heterozygosity.

Experimental evolution of recombination and crossover interference in Drosophila caused by directional selection for stress-related traits.

Background: Population genetics predicts that tight linkage between new and/or pre-existing beneficial and deleterious alleles should decrease the efficiency of natural selection in finite populations. By decoupling beneficial and deleterious alleles and facilitating the combination of beneficial alleles, recombination accelerates the formation of high-fitness genotypes. This may impose indirect selection for increased recombination.

Divergence of Drosophila melanogaster repeatomes in response to a sharp microclimate contrast in Evolution Canyon, Israel.

Repeat sequences, especially mobile elements, make up large portions of most eukaryotic genomes and provide enormous, albeit commonly underappreciated, evolutionary potential. We analyzed repeatomes of Drosophila melanogaster that have been diverging in response to a microclimate contrast in Evolution Canyon (Mount Carmel, Israel), a natural evolutionary laboratory with two abutting slopes at an average distance of only 200 m, which pose a constant ecological challenge to their local biotas. Flies inhabiting the colder and more humid north-facing slope carried about 6% more transposable elements than those from the hot and dry south-facing slope, in parallel to a suite of other genetic and phenotypic differences between the two populations.

Genome differentiation of Drosophila melanogaster from a microclimate contrast in Evolution Canyon, Israel.

The opposite slopes of "Evolution Canyon" in Israel have served as a natural model system of adaptation to a microclimate contrast. Long-term studies of Drosophila melanogaster populations inhabiting the canyon have exhibited significant interslope divergence in thermal and drought stress resistance, candidate genes, mobile elements, habitat choice, mating discrimination, and wing-shape variation, all despite close physical proximity of the contrasting habitats, as well as substantial interslope migration. To examine patterns of genetic differentiation at the genome-wide level, we used high coverage sequencing of the flies' genomes.

Rapid effects of humidity acclimation on stress resistance in Drosophila melanogaster.

We tested the hypothesis whether developmental acclimation at ecologically relevant humidity regimes (40% and 75% RH) affects desiccation resistance of pre-adults (3rd instar larvae) and adults of Drosophila melanogaster Meigen (Diptera: Drosophilidae). Additionally, we untangled whether drought (40% RH) acclimation affects cold-tolerance in the adults of D. melanogaster.

Differential expression of small heat shock protein genes Hsp23 and Hsp40, and heat shock gene Hsr-omega in fruit flies (Drosophila melanogaster) along a microclimatic gradient.

We examined the role of small Hsp genes (Hsp23 and Hsp40) and heat shock gene Hsr-omega in the thermoadaptation of Drosophila melanogaster inhabiting a highly heterogeneous microsite (Nahal Oren canyon, Carmel massif, Israel). We tested whether interslope differences in Drosophila thermoadaptation, revealed in our previous studies, are associated with the differential expression of these genes. Our results demonstrate an increased expression of the Hsp40 gene in thermotolerant lines subjected to mild heat shock treatment (P < 10(-6), analysis of variance test).

Drosophila flies in "Evolution Canyon" as a model for incipient sympatric speciation.

The genetic basis of population divergence leading to adaptive radiation and speciation is a major unresolved problem of evolutionary biology. Molecular elucidation of "speciation genes" advanced recently, yet it remains without clear identification of the gene complexes participating in reproductive isolation between natural populations, particularly, in sympatry. Genetic divergence was discovered between Drosophila melanogaster populations inhabiting ecologically contrasting, opposite slopes in "Evolution Canyon" (EC), Mt.

Assortative mating in Drosophila adapted to a microsite ecological gradient.

Elucidating the causes of population divergence, and ultimately speciation, is a central objective of evolutionary biology. A number of previous studies of Drosophila populations from the Nahal Oren canyon (Mt Carmel, Israel) revealed significant interslope differences for a complex of fitness and behavioral traits. Peculiarities in courtship song patterns and nonrandom mating were observed, despite a small interslope distance.

DNA repair efficiency and thermotolerance in Drosophila melanogaster from "Evolution Canyon".

The repair efficiency of four thermotolerant and four thermosensitive isofemale lines of Drosophila melanogaster originating from "Evolution Canyon" (Mt Carmel, Israel) was tested using 2-acetylaminofluorene (2-AAF) as mutagen. First, males of the standard laboratory line Canton S were treated with either 2-AAF solution or control solution. Then, females of the "Evolution Canyon" lines were crossed with treated (2-AAF or control solution) males and maintained at either 24 or 29 degrees C.

Sexual differences for emigration behavior in natural populations of Drosophila melanogaster.

Evolutionary biology considers migration behavior as central in genetic structure of populations and speciation. Here we report on emigration patterns in Drosophila melanogaster behavior under laboratory conditions. For this study, a special apparatus was employed that includes a few important changes in its design and size compared with other known systems.