Detrimental impact of a heatwave on male reproductive behaviour and fertility

Understanding how heatwaves impact on different aspects of mating behaviour and fertility is getting increasingly important. In this context, laboratory fertility and mating experiments involving manipulation and exposure of insects to different thermal conditions are common procedures. To conduct such experiments practical methods such as dyes are needed for an easy, non-invasive discrimination of individuals. We report here a study measuring the effect of an extended heat stress applied to males on several parameters of mating behaviour and fertility of laboratory populations of Drosophila subobscura derived from two distinct European locations. We found highly detrimental effects of heatwave on mating behaviour—with longer (courtship and copulation) latencies and lower mating occurrence but no changes in mating duration—and fertility, with reduced fecundity and reproductive success. Furthermore, we also tested the efficacy of food dye as a marker for individual discrimination and mating occurrence. While food dye did not allow to infer the occurrence of a mating based on a transfer of coloration from male to female, it did not affect mating and fertility, attesting its utility has a method for discriminating individuals within mating experiments in the context of thermal studies. Importantly, despite the fact that the heatwave was only applied in males, we observed an impact on behaviour of females that mated with stressed males, by often refusing their nuptial feeding. This opens possibilities for further integrated research on the changes of female and male mating behaviour and fertility under different thermal scenarios.info:eu-repo/semantics/publishedVersio

Slow and population specific evolutionary response to a warming environment

Adaptation to increasingly warmer environments may be critical to avoid extinction. Whether and how these adaptive responses can arise is under debate. Though several studies have tackled evolutionary responses under different thermal selective regimes, very few have specifically addressed the underlying patterns of thermal adaptation under scenarios of progressive warming conditions. Also, considering how much past history affects such evolutionary response is critical. Here, we report a long-term experimental evolution study addressing the adaptive response of Drosophila subobscura populations with distinct biogeographical history to two thermal regimes. Our results showed clear differences between the historically differentiated populations, with adaptation to the warming conditions only evident in the low latitude populations. Furthermore, this adaptation was only detected after more than 30 generations of thermal evolution. Our findings show some evolutionary potential of Drosophila populations to respond to a warming environment, but the response was slow and population specific, emphasizing limitations to the ability of ectotherms to adapt to rapid thermal shifts.info:eu-repo/semantics/publishedVersio

Mating behaviour and fertility of a monandrous insect under thermal stress

Tese de mestrado, Biologia Evolutiva e do Desenvolvimento, 2023, Universidade de Lisboa, Faculdade de CiênciasInsects are amongst the organisms most affected by rising temperatures, due to negative repercussions on life-history traits and, consequently, on population persistence. In many taxa males become sterile at lower temperatures than females. In these species, females could buffer the negative effect on male fertility improving their own reproductive output by rejecting sterile males or mating with more than one male. However, this rescue is conditioned by the populations’ mating system and the mating behaviour of both sexes, which can also be disrupted by temperature. Unfortunately, most work has studied polyandrous species leaving a gap in our knowledge. Thus, understanding if and how monandrous species change their mating behaviour and/or mating system due to heat stress will bring important knowledge on the crucial topic of population persistence under climate warming. Here, we studied the real-time evolution of two bio-geographical distinct populations of a monandrous fruit fly (Drosophila subobscura) subjected to a global warming scenario. As such, we could test if selection and population history play a role in the ability to respond to temperature changes. Specifically, we aimed to assess: i) whether adaptation to a warming environment occurs; ii) the impact of high temperatures on male mating behaviour and fertility; and iii) the impact of reduced male fertility on female mating behaviour, fertility, and propensity to remate. We show that adaptation to warming conditions was population-specific and occurred with no evident costs. We also demonstrate that exposure to high temperatures leads to lower performance in males, affecting both behaviour and fertility. Importantly, these males are able to recover a functional mating behaviour through time, but not their reproductive output. Finally, we show that monandrous females remate after exposure to heat-stressed males and that this behaviour is advantageous for the reproductive output of the female leading to a total rescue of their reproductive performance in certain conditions. Ultimately, this project brings new insights on the effects of high temperatures on mating behaviour and fertility in a monandrous species and provide a model to assess how a shift from monandry to polyandry affects species at both the individual and the population levels

Sex and population differences underlie variation in reproductive success in a warming environment

Current rising temperatures are threatening biodiversity. It is therefore crucial to understand how climate change impacts on male and female fertility and whether evolutionary responses can help in coping with heat stress. We use experimental evolution to study male and female fertility during real-time evolution of two historically differentiated populations of Drosophila subobscura under different thermal selection regimes for 23 generations. We aim to (1) tease apart sex-specific differences in fertility after exposure to warming conditions during development, (2) test whether thermal selection can enhance fertility under thermal stress, and (3) address the role of historically distinct genetic backgrounds. Contrary to expectations, heat stress during development had a higher negative impact on female fertility than on male fertility. We did not find clear evidence for enhanced fertility in male or females evolving under warming conditions. Population history had a clear impact on fertility response under thermal stress, particularly in males with those from lower latitude presenting better performance than their higher latitude counterparts. We show that the impact of thermal stress on fertility varies between traits, sexes and genetic backgrounds. Incorporating these several levels of variation is crucial for a deeper understanding of how fertility evolves under climate change.info:eu-repo/semantics/acceptedVersio

Past history shapes evolution of reproductive success in a global warming scenario

Adaptive evolution is critical for animal populations to thrive in the fast-changing natural environments. Ectotherms are particularly vulnerable to global warming and, although their limited coping ability has been suggested, few real-time evolution experiments have directly accessed their evolutionary potential. Here, we report a long-term experimental evolution study addressing the evolution of Drosophila thermal reaction norms, after ∼30 generations under different dynamic thermal regimes: fluctuating (daily variation between 15 and 21 °C) or warming (daily fluctuation with increases in both thermal mean and variance across generations). We analyzed the evolutionary dynamics of Drosophila subobscura populations as a function of the thermally variable environments in which they evolved and their distinct background. Our results showed clear differences between the historically differentiated populations: high latitude D. subobscura populations responded to selection, improving their reproductive success at higher temperatures whereas their low latitude counterparts did not. This suggests population variation in the amount of genetic variation available for thermal adaptation, an aspect that needs to be considered to allow for better predictions of future climate change responses. Our results highlight the complex nature of thermal responses in face of environmental heterogeneity and emphasize the importance of considering inter-population variation in thermal evolution studies.info:eu-repo/semantics/acceptedVersio

Heat-induced female biased sex ratio during development is not mitigated after prolonged thermal selection

Abstract Background The negative impacts of climate change on biodiversity are consistently increasing. Developmental stages are particularly sensitive in many ectotherms. Moreover, sex-specific differences in how organisms cope with thermal stress can produce biased sex ratios upon emergence, with potentially major impacts on population persistence. This is an issue that needs investigation, particularly testing whether thermal selection can alleviate sex ratio distortions in the long-term is a critical but neglected issue. Here, we report an experiment analyzing the sex ratio patterns at different developmental temperatures in Drosophila subobscura populations subjected to long-term experimental evolution (~ 30 generations) under a warming environment. Results We show that exposure to high developmental temperatures consistently promotes sex ratio imbalance upon emergence, with a higher number of female than male offspring. Furthermore, we found that thermal selection resulting from evolution in a warming environment did not alleviate such sex ratio distortions generated by heat stress. Conclusions We demonstrate that heat stress during development can lead to clear sex ratio deviations upon emergence likely because of differential survival between sexes. In face of these findings, it is likely that sex ratio deviations of this sort occur in natural populations when facing environmental perturbation. The inability of many insects to avoid thermal shifts during their (more) sessile developmental stages makes this finding particularly troublesome for population subsistence in face of climate warming events