How do organisms develop in a variable environment?
If you have ever experienced a sudden heat wave, you know that temperature change is not gradual. In fact, short-term extreme heating is an ecologically realistic scenario. Variation in physiological responses to such acute heat "stress" determine which individuals can “take the heat” and which ones can't. The underlying molecular targets of thermal stress are macromolecules that support cellular processes. Cells possess damage-control mechanisms that confer tolerance to thermal stress. But cells are also quite vulnerable. To illustrate thermal sensitivity at the cellular level, the movie below shows what happens to mitosis in an early fruit fly embryo when it is exposed to high temperature. Note how the second wave of nuclear divisions becomes arrested and results in mitotic nondisjunction.
How do embryos orchestrate mitotic divisions and maintain normal development in the face of environmental stress?
We are approaching this question by testing the role of specific candidate genes to confer thermal tolerance during development in the fruit fly Drosophila melanogaster. In particular, we are investigating how gene-specific maternal effects influence early developmental processes and whole-organism survival during and after temperature stress (For more info check out our paper -- at Journal of Experimental Biology here).
To complement our manipulation of candidate genes in the developing fly embryo, we are utilizing confocal fluorescence microscopy to characterize cellular responses to environmental stress in real time (see video above). Ultimately, our goal is to define the link between gene and protein expression and the maintenance of critical cellular structures. This research will have a broad impact by contributing to our basic knowledge of how cells respond to environmental stress and by identifying candidate pathways that are the basis of stress tolerance at both the cellular and whole-organism levels.
We are approaching this question by testing the role of specific candidate genes to confer thermal tolerance during development in the fruit fly Drosophila melanogaster. In particular, we are investigating how gene-specific maternal effects influence early developmental processes and whole-organism survival during and after temperature stress (For more info check out our paper -- at Journal of Experimental Biology here).
To complement our manipulation of candidate genes in the developing fly embryo, we are utilizing confocal fluorescence microscopy to characterize cellular responses to environmental stress in real time (see video above). Ultimately, our goal is to define the link between gene and protein expression and the maintenance of critical cellular structures. This research will have a broad impact by contributing to our basic knowledge of how cells respond to environmental stress and by identifying candidate pathways that are the basis of stress tolerance at both the cellular and whole-organism levels.
Thermal adaptation hinges upon early life stages.
Consider that any difference in thermal tolerance across life stages will cause the most thermally sensitive life stage to be the one that is most likely to undergo selective mortality. Thus, we must understand the physiological basis of thermal traits throughout the life cycle in order to predict how species respond to thermal extremes.
We are comparing thermal tolerance of adults and embryos among natural populations of Drosophila melanogaster from a broad range of thermal habitats around the globe to assess natural variation of thermal tolerance in mobile vs. immobile life stages. Amazingly, we find no variation among populations in adult thermal tolerance, but embryonic thermal tolerance is higher in tropical strains than in temperate strains. Our findings suggest that thermal selection has led to divergence in embryonic thermal tolerance but that selection for divergent thermal tolerance may be limited in adults. Further, our results suggest that thermal traits should be measured across life stages in order to better predict adaptive limits. For more information check out our papers -- at Proceedings of the Royal Society B here and Journal of Evolutionary Biology here.
We are comparing thermal tolerance of adults and embryos among natural populations of Drosophila melanogaster from a broad range of thermal habitats around the globe to assess natural variation of thermal tolerance in mobile vs. immobile life stages. Amazingly, we find no variation among populations in adult thermal tolerance, but embryonic thermal tolerance is higher in tropical strains than in temperate strains. Our findings suggest that thermal selection has led to divergence in embryonic thermal tolerance but that selection for divergent thermal tolerance may be limited in adults. Further, our results suggest that thermal traits should be measured across life stages in order to better predict adaptive limits. For more information check out our papers -- at Proceedings of the Royal Society B here and Journal of Evolutionary Biology here.
Population sampling locations in cool sites in North America and warm tropical sites around the globe.
Adults from all over the world have the same thermal tolerances. Embryos from the tropics are more heat tolerant. *ANOVA, P < 0.05.