Argyrochosma jonesii includes two sexually reproducing cytotypes. The diploid is known from a few localities in the Sonoran and Mojave Deserts; the tetraploid is found throughout the Mojave Desert and cismontane southern California. Although subtle morphologic differences exist between these cytotypes, they are distinguished primarily by characteristics known to correlate with increases in ploidy level (such as spore size and the length of stomatal guard cells). Further investigation is necessary to determine whether the tetraploid arose through autopolyploidy or hybridization between cryptic species.