UC San Diego

In eukaryotes, both mitochondrial and nuclear genes encode subunits of electron transport system (ETS) enzymes that must favorably interact (mitonuclear interactions) to produce metabolic energy. Therefore, mitochondrial and nuclear genes coevolve within populations such that hybrids bred from populations in different geographic locations may result in mitonuclear incompatibilities, leading to hybrid breakdown in numerous phenotypic traits. Current hybrid studies of intertidal copepods reveal the effects of mitonuclear interactions in the breakdown of developmental times, ATP production, and survival; however, the linkages amongst numerous phenotypic traits are still largely unknown. To determine the extent of breakdown of phenotypic traits and their linkages to one another, we recorded developmental times and monitored longevity after categorizing copepods into fast-developing and slow-developing groups. Contrary to previous studies, we found that mitonuclear incompatibilities did not greatly affect the developmental times in hybrids. Additionally, individuals from the slow-developing groups for each of the crosses showed higher survivorship to day 89 than the fast-developing group; i.e., there was an apparent tradeoff between early life stage developmental rates and longevity where fast-developing individuals displayed shorter lifespans compared to slow-developing individuals. Future studies should examine the effects of different rates of development on longevity and potentially when the tradeoff starts between fast early life stage development and a shorter lifespan. Other potential future directions include measuring different life history traits alongside longevity such as lifetime egg production in females.