What doesnt kill you makes you stronger

Abstract

newline The fitness of an organism is determined by its ability to survive and reproduce in an newlineenvironment. Resources available to an organism during its juvenile stages have a huge newlineimpact on its adult fitness. This is especially true for holometabolous insects, where newlinemost of the resource acquisition for the adult stages happens during the larval stages. newlineBecause of the poor locomotor abilities during the larval stage, the egg-laying site newlinebecomes the feeding site for larvae, which at times leads to a larval crowding newlineenvironment. Quite often, this exposes larvae to high competition for resources and an newlineenvironment full of highly toxic excretory waste during juvenile stages. Populations newlinefacing such larval crowding every generation should be selected by natural selection to newlineoptimize the distribution of limited resources in traits of high fitness importance. A major newlinetheme of my Ph.D. thesis was to investigate reproductive and stress-related traits in newlineadults of a population that are experimentally evolved to adapt to larval crowding newlineconditions. newlineI have used eight large outbred laboratory populations of Drosophila melanogaster in newlinemy experiments, four of which have been experimentally selected for adaptation to newlinelarval crowding for more than 250 generations now, whereas the other four populations newlineare non-larval crowded control populations. I aimed to investigate the evolutionary newlineconsequences of adaptation to a poor juvenile environment on adult fitness. Hence, I newlinehave looked into reproductive traits and stress-tolerance-related traits in adults of these newlinepopulations. For reproductive traits, I looked into the evolution of investment in newlinereproductive newlinetissues newline(testis newlineand newlineaccessory newlinegland newlinesize), newlinesperm newlinecompetition, newlinesexual-conflict levels, re-mating frequencies. To investigate the evolution of the newlinestress-tolerance ability of these populations, I have looked at the immune response and newlineheat-stress tolerance ability of adults. The findings of these studies have given aninsight into the completely unexplored territory of the evo