Search

The canalization concept (1) describes the resistance of a developmental process to phenotypic variation, regardless of genetic and environmental perturbations, owing to the existence of buffering mechanisms. Severe perturbations, which overcome such buffering mechanisms, produce altered phenotypes that can be heritable and can themselves be canalized by a genetic assimilation process. An important implication of this concept is that the buffering mechanism could be genetically controlled. Recent studies on Hsp90, a protein involved in several cellular processes and development pathways (2-5), indicate that it is a possible molecular mechanism for canalization and genetic assimilation. In both flies and plants, mutations in the Hsp90-encoding gene induce a wide range of phenotypic abnormalities, which have been interpreted as an increased sensitivity of different developmental pathways to hidden genetic variability (6,7). Thus, Hsp90 chaperone machinery may be an evolutionarily conserved buffering mechanism of phenotypic variance, which provides the genetic material for natural selection. Here we offer an additional, perhaps alternative, explanation for proposals of a concrete mechanism underlying canalization. We show that, in Drosophila, functional alterations of Hsp90 affect the Piwi-interacting RNA (piRNA; a class of germ-line-specific small RNAs) silencing mechanism leading to transposon activation and the induction of morphological mutants. This indicates that Hsp90 mutations can generate new variation by transposon-mediated 'canonical' mutagenesis., In Drosophila, primary spermatocytes of Hsp90 mutant males exhibit crystalline aggregates (8,9) (see also Fig. 1b), usually absent in wild-type testes (Fig. 1a), the formation of which is due to [...]

Phenotypic plasticity is generally explained as the result of epigenetic mechanisms modifying gene expression in response to changing environmental conditions. However, the biology of transposable elements (TEs) suggests that such elements may also induce differential gene expression by affecting regulatory regions.We discuss the ecological and evolutionary relevance of epigenetic modifications versus transposon activity, taking into account that epigenetic modifications are generally reversible but that the modifications induced by TEs are stably inherited.We outline our perspective on the multiple roles played by environmental changes in the context of adaptive evolution. Environmental perturbations can induce phenotypic variations via epigenetic modulation of gene expression and promote, at the same time, genetic variability by triggering bursts of TE activity; finally, they select which genetic variations are most advantageous for survival.Within this context, the production of environmentally induced advantageous phenotypes by epigenetic mechanisms could represent an immediate process of adaptation followed by TE‐induced genotypic changes that make these phenotypic variants heritable through the germ line. This scenario could lead TEs to play different roles in the function of the time‐scale of ecological variation, such as those related to climatic change in the current context of global change.In conclusion, we propose that through TE activation, environmental changes can act as inducers of genetic variability, upon which they also act as selective forces, thus triggering rapid evolutionary processes. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

The knowledge of the endemic drosophilid assemblage is a useful reference to study population dynamics when new species are introduced in a geographical area. The introduction of invasive species can change the structure of the drosophilid community; hence, the distribution data for endemic species are also essential to support efficient pest management. We provide the first description of the natural drosophilid populations (Diptera Drosophilidae) recorded in Apulia, in Southern Italy. The flies, which were collected in a field survey throughout a year, were classified by morphological and molecular analyses by sequencing the barcode fragment of the COI mtDNA gene. The identified species show a distribution of frequencies that varies throughout the year, reflecting a seasonal life cycle peculiar to each species. Among the recorded drosophilids, the potential pest species Drosophila suzukii represents one of the four most abundant species. [ABSTRACT FROM AUTHOR]