The genome sizes of ostracod crustaceans correlate with body size and phylogeny

46 47 Within animals a positive correlation between genome size and body size has been detected in 48 several taxa but not in others, such that it remains unknown how pervasive this pattern may be. 49 Here we provide another example of a positive relationship, in a group of crustaceans whose 50 genome sizes have not previously been investigated. We analyze genome size estimates for 46 51 species across Class Ostracoda, including 29 new estimates made using Feulgen image analysis 52 densitometry and flow cytometry. Genome sizes in this group range ~80-fold, a level of 53 variability that is otherwise not seen in crustaceans with the exception of some malacostracan 54 orders. We find a strong positive correlation between genome size and body size across all 55 species, including after phylogenetic correction. We additionally detect evidence of XX/XO sex 56 determination in all three species of myodocopids where male and female genome sizes were 57 estimated. On average, genome sizes are larger but less variable in myodocopids than in 58 podocopids, and marine ostracods have larger genomes than freshwater species, but this appears 59 to be explained by phylogenetic inertia. The relationship between phylogeny, genome size, body 60 size, and habitat is complex in this system, and will benefit from additional data collection across 61 various habitats and ostracod taxa. 62