Temperature fluctuations in the desert increases flies’ plasticity to overcome stressful periods depending on their parent’s environmental experience

Fernando Diaz, Bram Kuijper, Rebecca B. Hoyle, Nathaniel Talamantes, Joshua M. Coleman, Luciano M. Matzkin

Image taken and modified from the website of the Drosophila la in https://obbard.bio.ed.ac.uk/photos.html. © copyright 2010 Darren J Obbard

Organisms often exhibit a remarkable capacity to sense their environments and, based on this information, trigger different kinds of molecular and physiological process later in life that help them acclimate and overcome stressful periods. This capacity, known as phenotypic plasticity, can also be transferred to the next generation through maternal (or parental) mechanisms that induce a more fit response of their offspring, a transgenerational form of phenotypic plasticity. However, such flexibility comes with a physiological cost, and thus can only emerge through biological evolution when the cost/benefit is optimal. We propose that such conditions are more favored in fluctuating environments, and tested this hypothesis using Drosophila mojavensis, a fly species that develops as larvae and feeds as adults in necrotic tissues of cacti and inhabits the deserts of southwestern United States and northwestern Mexico. This species is composed of multiple genetically and environmentally distinct populations. Flies from the Sonoran Desert are exposed to more extreme and longer stressful periods when compared with flies living in Santa Catalina Island, California. We asked whether major environmental fluctuations in the desert would have favored the evolution of a higher thermal plasticity in early (larva) vs adult stages. But more importantly if this plasticity could also be transferred to their descendants as transgenerational effects, allowing them resist stress better. We discovered that early stages not only are more tolerant to heat, but they seem to “listen” more to their acclimated parents than when they are adults. This amazing plasticity was substantially increased in flies living in the Sonoran Desert vs the milder and more stable Mediterranean environment of Santa Catalina Island. We demonstrate that these differences are evolutionary adaptations to environmental predictability in fluctuating environments, providing insight into the role of such phenomena in the process of ecological adaptation. 

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