Meeting Abstract
Mitonuclear interactions are implicated in many evolutionary processes. Evidence suggests that they reduce fitness in individuals with mismatched mitochondrial and nuclear genomes, but this is poorly understood in natural populations. We investigated mitonuclear interactions in the beetle Chrysomela aeneicollis. Populations live along altitudinal transects that impose temperature and oxygen stress. We analyzed variation along a 75 km latitudinal transect and found that the nuclear metabolic enzyme locus PGI and mitochondrial protein-coding COII diverge more than other genes. We measured reproduction and development of BC beetles in nature and performance and infection level by Wolbachia bacteria in the laboratory. We found that females homozygous for the PGI genotype common in northern populations laid more eggs if they had the mitochondrial haplotype common in the north, while females homozygous for the PGI allele most common in south laid more eggs if they had the southern haplotype. Larval development showed a similar pattern. In the laboratory, adults with matched genotypes ran faster and had higher mitochondrial enzyme activities than those with mismatched genotypes, especially after heat exposure. In contrast, running speed and male mating success showed mismatch at low elevation, suggesting that environmental hypoxia may affect mitonuclear interactions. Finally, we found that Wolbachia level is negatively related to recovery from thermal stress exposure, but the pattern depends on mitochondrial and nuclear genotype. Taken together, these data suggest that mitonuclear interactions significantly alter performance and fitness in beetles living along natural thermal and oxygen gradients.
