Small genomes in most mites (but not ticks)

Given their ecological and socioeconomic importance, it is not surprising that a number of mites (including ticks) have been the targets of recent genome sequencing projects. Less easily explained is why data on fundamental genetic parameters such as genome size (i.e. haploid DNA content) are greatly lacking for such a diverse and important group. Here, we compile the available genome size data for ticks and other mites, and add new estimates for another 20 species. We report a notable distinction in genome size between the comparatively larger genomes of ticks versus the (sometimes extremely) small genomes of non-tick mites. We also find a positive correlation between genome size and body size across mites, and explore some of the possible causes of the variability in genome size that exists among acarine species.