College of Liberal Arts & Sciences
BA (Bachelor of Arts)
Session and Year of Graduation
Honors Major Advisor
For my Honors Research in the Neiman lab at the University of Iowa, I evaluated phenotypic variation in nuclear and mitochondrially (mt) encoded fitness-relevant traits in a New Zealand freshwater snail, Potamopyrgus antipodarum, within the context of sexual conflict and reproductive mode polymorphism. Sexual conflict occurs when the genetic interest of males and females diverge. That is, traits that are advantageous to one sex may be harmful to the other. My research focused on intralocus sexual conflict, involving different optima for a trait expressed in both sexes. My methodology included three assays, chosen to examine traits that are influenced by both the nuclear and mt genome. First, I used the righting assay, defined as the time that it takes for snails to return to an upright position after being flipped to the ventral side. Righting time increases with temperature in P. antipodarum, indicating that elevated temperatures induce stress. Second, the boldness assay quantified important elements of snail temperament and behavior, traits with important fitness and ecological consequences. Third, I used the JC-1 assay, which measures ATP synthase activity in extracted live mitochondria, to compare mitochondrial function across sexes and reproductive modes. I found that mean righting time and emergence time were affected both by temperature and the interaction between lake and temperature. These results suggest that variation in nuclear and mt-encoded fitness-relevant traits are more heavily influenced by population of origin and heat stress than sex or reproductive mode. I did detect a significant interaction between both sex and reproductive mode and lake and reproductive mode on JC-1 fluorescence, suggesting that maternal inheritance and mode of inheritance affect mitochondrial function. This latter result hints that mutation accumulation might influence mitochondrial performance and that organismal function may be dependent on the interaction of nuclear and mitochondrial genomes. Because reproductive mode is in turn expected to have a major influence on the evolution of mitonuclear interactions, my results set the stage for more direct study of the evolutionary dynamics of these interactions in a sexual vs. asexual context.
sexual conflict, sexual reproduction, asexual reproduction, Potamopyrgus antipodarum, mitochondria
Copyright © 2017 Emma Greimann