Genome Size and Host Specialization in Parasites

In parasites, there are several examples of changes in genome size linked to a parasitic lifestyle—with some species having greatly reduced or expanded genome sizes relative to free-living non-parasitic relatives. What is unknown is whether there is correlated evolution between genome size and host specialization, and whether there is a generalizable framework in predicting genome size evolution in parasites using their genetic architecture and host use ecology. Here, I tested whether genome size of 96 eukaryotic parasites across a wide variety of taxa correlates with host specialization, quantified by the number and phylogenetic relatedness of host species they parasitize. I did not find that genome size and host specialization shared a correlated phylogenetic history; however, I did find that ectoparasites tended to have larger genomes then endoparasites, and that parasitic fungi had more host species then either animal or protozoan parasites. Although no clear trends in the evolution of genomes and host specificity were observed among parasites, my study was significantly limited by gaps in both genome size and host range availability. Future research should seek to address these gaps, as well as improve taxonomic coverage of data, so that trends in the evolution of parasite genome architecture could be adequately tested and delineated