Abstract

BackgroundIn insect species like Drosophila melanogaster, evolution of increased resistance or evolution of particular traits under specific environmental conditions can lead to energy trade-offs with other crucial life-history traits. Adaptation to cold stress can, in principle, involve modification of reproductive traits and physiological responses. Reproductive traits carry a substantial cost; and therefore, the evolution of reproductive traits in response to cold stress could potentially lead to trade-offs with other life-history traits. We have successfully selected replicate populations of Drosophila melanogaster for increased resistance to cold shock for over 33 generations. In these populations, the ability to recover from cold shock, mate, and lay fertile eggs 24 h post cold shock is under selection. These populations have evolved a suite of reproductive traits including increased egg viability, male mating ability, and siring ability post cold shock. These populations also show elevated mating rate both with and without cold shock. In the present study, we quantified a suite of life-history related traits in these populations to assess if evolution of cold shock resistance in these populations comes at a cost of other life-history traits.ResultsTo assess life-history cost, we measured egg viability, mating frequency, longevity, lifetime fecundity, adult mortality, larva to adult development time, larvae to adults survival, and body weight in the cold shock selected populations and their controls under two treatments (a) post cold chock and (b) without cold shock. Twenty-four hours post cold shock, the selected population had significantly higher egg viability and mating frequency compared to control populations indicating that they have higher cold shock resistance. Selected populations had significantly longer pre-adult development time compared to their control populations. Females from the selected populations had higher body weight compared to their control populations. However, we did not find any significant difference between the selected and control populations in longevity, lifetime fecundity, adult mortality, larvae to adults survival, and male body weight under the cold chock or no cold shock treatments.ConclusionsThese findings suggest that cold shock selected populations have evolved higher mating frequency and egg viability. However, there is no apparent life-history associated cost with the evolution of egg viability and reproductive performances under the cold stress condition.

Highlights

  • In insect species like Drosophila melanogaster, evolution of increased resistance or evolution of particular traits under specific environmental conditions can lead to energy trade-offs with other crucial life-history traits

  • Experiment 1: egg viability and mating frequency After 24 generations of selection, we first wanted to investigate that if there was a primary response to selection for cold shock resistance

  • We assayed the evolution of cold shock resistance in terms of (a) egg viability 24–30 h post cold shock and (b) mating frequency over the first 36 h post cold shock

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Summary

Introduction

In insect species like Drosophila melanogaster, evolution of increased resistance or evolution of particular traits under specific environmental conditions can lead to energy trade-offs with other crucial life-history traits. We have successfully selected replicate populations of Drosophila melanogaster for increased resistance to cold shock for over 33 generations In these populations, the ability to recover from cold shock, mate, and lay fertile eggs 24 h post cold shock is under selection. The ability to recover from cold shock, mate, and lay fertile eggs 24 h post cold shock is under selection These populations have evolved a suite of reproductive traits including increased egg viability, male mating ability, and siring ability post cold shock. One important way in which organisms cope with immediate temperature changes (heat shock and cold shock) is by expressing heat shock proteins (Hsps) Expression of these proteins is extremely costly and affects reproduction [21]. Investment in resisting temperature shock can lead to energy-based trade-offs with other important life-history traits [22,23,24,25]

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