29.2 Friday, Jan. 4 Symbiont transmission and maintenance of interspecific disequilibrium in structured populations FITZPATRICK, B. M.; Univ. of Tennessee email@example.com
Microbial symbioses might be as ubiquitous and influential as genes in the evolution and development of some plant and animal phenotypes, and in some cases (e.g., mitochondria) the line is blurred between symbiont and host. Here I explore the proposition that host-symbiont relationships lie on a continuum from the intimacy of genes and organelles to the indifference of casually co-occurring species. A key question is whether symbiont transmission is similar enough to Mendelian gene transmission to generate and maintain associations between genomes that can evolve in the same way as conventional genotypes. I show that intergenomic associations can be described by the same basic models used for conventional linkage disequilibrium with one critical difference: recombination between genes ranges from 0.0 to 0.5, whereas recombination between host and symbiont ranges from 0.0 to 1.0. Thus, covariance between host and symbiont genomes depends on population history, geographic structure, selection, and vertical transmission rate, just as disequilibrium between genes within a genome. Host-symbiont coevolution can be affected by intergenomic epistasis and nonrandom mating just as coevolution between genes within a conventional genome. I illustrate the theoretical continuum between multilocus genetics and host-symbiont dynamics with a simple hybrid zone model where interspecific disequilibrium is maintained by population structure, and a reformulation of a gene-culture coevolution model with humans as hosts and cattle as symbionts.