Tropical Ectotherm Can't Handle the Heat: Simulated Climate Warming Effects on Fitness Traits and Gene Expression in Cordylochernes scorpioides

Abstract

Climate warming has been predicted to severely impact tropical biodiversity due to its effect on ectotherm metabolism, which increases exponentially with temperature. Many studies have shown that size is reduced in arthropods to compensate for the stress of increased temperature. However, since tropical ectotherms already function close to their thermal limits, metabolic stress is expected to affect not only morphology but also survival and reproduction. Mitochondria play a critical role in metabolism by producing energy for the cells, yet how mitochondrial variation may mitigate climate warming effects is poorly understood. Previous research on the pseudoscorpion, Cordylochernes scorpioides, has shown direct negative effects of climate warming on this neotropical ectotherm, as well as differential responses to increased temperature by highly divergent mitochondrial haplogroups. The present study utilized a simulated climate warming design to investigate the effects of moderate thermal stress (2.5°C increase) and mitochondrial haplogroup on life history, adult morphological traits, and reproductive traits in C. scorpioides. Additionally, a recently assembled, whole C. scorpioides genome sequence was used to identify nuclear genes differentially expressed in testicular tissue of control- versus high-temperature males, including transposable element-derived genes which may have become activated due to epigenetic deregulation. The findings show that even a moderate temperature increase can be detrimental to the survival of this species and potentially other tropical ectotherms, which may have a negative domino effect on global biodiversity.