What accounts for the immense variation in genome size and structure is a fundamental biological question. Changes in organismal traits related to genome use and inheritance offer powerful settings to study genome evolution. Sexual reproduction is a hallmark trait for eukaryotes and transitions to asexuality should greatly impact evolutionary processes. I examined genomic consequences of asexuality in the freshwater snail, Potamopyrgus antipodarum, characterized by frequent transitions from sexual to asexual reproduction.