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Simulated climate warming and mitochondrial haplogroup modulate small non-coding RNA expression in the neotropical pseudoscorpion, Cordylochernes scorpioides
AuthorSu, Eleanor J.
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While the plight of polar bears in a rapidly warming world is much publicized, recent theory suggests that the organisms likely to be most at risk from rising temperatures are terrestrial arthropods and reptiles inhabiting the tropics. Metabolic rate in such ectothermic species increases exponentially with ambient temperature, and a small temperature increase in a warm environment therefore has a much larger physiological impact than a comparable temperature increase in a cool environment. In a recently published study on the neotropical pseudoscorpion, Cordylochernes scorpioides, simulated climate warming significantly decreased survival, average values for morphological traits, and level of sexual dimorphism. However, these effects were minor compared to catastrophic consequences for male fertility and female fecundity, identifying reproduction as the life history stage most vulnerable to climate warming. Still to be investigated, however, was the potential for epigenetically and genetically based responses to elevated temperature. Here, I examined the effects of chronic high-temperature exposure on epigenetic regulation in C. scorpioides in the context of naturally occurring variation in mitochondrial DNA. Epigenetic mechanisms, including DNA methylation, histone modification, and small noncoding RNA (sncRNA) expression, are particularly sensitive to environmental factors such as temperature, which can induce physiological stress and bring about changes in epigenetic states and phenotypes that may be heritable across generations. My results indicate that exposure of male pseudoscorpions to elevated temperature significantly altered the expression of sncRNAs, specifically microRNAs and piwi-interacting RNAs, in testicular tissue. Mitochondrial haplogroup was also a significant factor influencing both sncRNAs and mitochondrial gene expression. These findings demonstrate that chronic heat stress alters epigenetic profiles that may at least partially account for reduced reproductive function in male C. scorpioides. Moreover, through its effects on epigenetic regulation, mitochondrial DNA polymorphism may provide the potential for an adaptive evolutionary response to climate warming. Since tropical terrestrial arthropods constitute the vast majority of animal species, the results of this study have important implications for understanding the consequences of climate change for global biodiversity.