Sinergistički efekat genomskog i sredinskog stresa u dve populacije Drosophila subobscura

Abstract

Jedinke uzorkovane iz dva ekološki različita staništa, i hibridi nastali njihovim ukrštanjem (unutar-linijski, unutar-populacioni i među-populacioni) izlagane su povećanoj koncentraciji olova, čime je omogućeno da se utvrdi razlika u odgovoru jedinki različitog nivoa heterozigotnosti genoma na sredinski stres odnosno, testira hipoteza o heterozigotnoj superiornosti u stresnim uslovima i utvrdi populaciono specifičan odgovor na prisustvo olova. Sinergistički efekat stresa evaluiran je na tri nivoa: populacionom - analizom komponenti adaptivne vrednosti (dužina razvića i preživljavanje od jaja do adulta), morfološkom – analizom varijabilnosti veličine krila i biohemijskom - praćenjem ekspresije proteina toplotnog šoka. Rezultati su pokazali redukciju svih ispitivanih osobina kod inbredovanih jedinki i njihovo povećanje kod jedinki sa višim nivoom heterozigotnosti genoma, potvrđujući hipotezu heterozigotne superiornost koja se intenzivira u stresnim uslovima. Uočen je trend sinergističkog efekta genomskog i sredinskog stresa za komponente adaptivne vrednosti, koji je statistički značajan za veličinu krila, s obzirom da je najintenzivnija redukcija primećena kod inbredovanih jedinki u stresnim uslovima. Nije dobijen populaciono specifičan odgovor u prisustvu olova, ali je utvrđeno da na ishod međupopulacione hibridizacije u stresnim uslovima veliki uticaj ima poreklo ženke i evoluciona istorija njene prirodne populacije. Može se zaključiti da je održavanje genetičke varijabilnosti od velike važnosti za opstanak populacija, i da čak i nizak stepen inbridinga utiče na pad adaptivne vrednosti, naročito u stresnim uslovima sredine.

The subject of this dissertation is population genetic analysis of synergistic effect of genomic and environmental stress in model species Drosophila subobscura. Individuals sampled from two ecologically distinct habitats, and their hybrids with different levels of genome heterozygosity (intra-line, intra-population and inter-population hybrids) were exposed to elevated concentrations of lead, aiming to test hypothesis of heterozygote superiority in stressful conditions and detect population specific response to lead pollution. Synergistic effect of stress was evaluated at three levels: population - through analysis of fitness components (development time and egg-to-adult survival), morphological - through analysis of variability in the wings size and biochemical – through the expression of heat shock protein. The results showed a reduction of all investigated traits in inbred individuals and their increase in those with higher levels of genome heterozygosity, confirming the hypothesis of heterozygote superiority which intensifies under stressful conditions. Analysis of fitness components indicates synergistic effect of genomic and environmental stress, and variance in wing size shows statistical significance, since the greatest reduction of all traits was observed in inbred groups. Population specific response to lead pollution was not detected, but significant influence of female origin on the outcome of between-population hybridization under stressful conditions was observed. It can be concluded that the maintenance of genetic variation is important for the survival of populations in changing environments, and even low levels of inbreeding lead to decline in adaptive value, especially in stressful environments.