Polyploid unisexual salamanders have higher tissue regeneration rates than diploid sexual relatives

Differences in genome composition are known to influence cell division and tissue growth, yet few studies have compared tissue growth between closely related taxa that vary in ploidy and genome composition. Whether cellular mechanisms scale to a functional trait such as tissue regeneration is important for understanding the ecological interactions between polyploids and closely related diploid taxa. We studied regeneration in unisexual Ambystoma salamanders, an ancient unisexual (all-female) lineage in which most individuals are triploids consisting of combinations of two or more distinct genomes from their sexual relatives. We discuss the aspects of haploid genome size and polyploidy that may contribute to variation in tissue regeneration and hypothesize that higher ploidy or variations in genome composition in unisexual Ambystoma would result in increased tissue regeneration compared to diploid sexual relatives, as polyploidy is generally associated with faster limb regeneration. We tested this hypothesis by comparing tail regeneration rates over 4 months between polyploid unisexual salamanders and sympatric diploid sexual salamanders under standardized laboratory conditions. Consistent with our prediction, unisexual Ambystoma regenerated tail tissue at approximately twice the rate of the sexual species. This result provides a physiological difference between unisexual and sexual salamanders that could influence their coexistence.