Why some North American salamanders steal genetic material to reproduce

Nature · Published 3 October 2026 Swipe more like this →

In short: Mole salamanders are a diverse group of North American amphibians, but some populations have evolved a bizarre reproductive strategy called kleptogenesis. Instead of relying on standard mating, these all-female groups hijack sperm from related species to trigger egg development, sometimes incorporating that DNA into their own complex, multi-species genomes.

The genus Ambystoma, established by Johann Jakob von Tschudi in 1839, comprises 32 extant species endemic to North America. While many species follow a typical life cycle—hatching as aquatic, gill-bearing larvae before undergoing metamorphosis into terrestrial adults—others exhibit neoteny, retaining larval traits like external gills throughout their entire lives. The axolotl is the most famous example of this phenomenon, which occurs when a salamander cannot naturally produce the thyroxine required for metamorphosis.

The most striking biological anomaly within the group is the existence of unisexual, all-female populations found across the Great Lakes and northeastern North America. These salamanders engage in kleptogenesis, a unique reproductive mode where they require sperm from a co-occurring species to initiate egg development. After using the sperm to trigger this process, the females may discard the paternal genome or incorporate it, leading to offspring with elevated ploidy. This results in individuals possessing nuclear DNA from up to five distinct species, such as the blue-spotted and tiger salamander.

Despite this nuclear complexity, all unisexual ambystomatids share a common maternal ancestor, making them the most ancient lineage of all-female vertebrates known to science. Research suggests this original hybridization event occurred between 2.4 and 3.9 million years ago. Because their hybrid genomes make them morphologically similar to their relatives, these unisexual salamanders are considered cryptic species. Their evolutionary history is further complicated by the fact that the A. laterale genome, which appears essential for their unisexuality, has been independently replaced multiple times across different lineages.

Beyond their reproductive quirks, mole salamanders are subjects of intense scientific interest due to their regenerative abilities. The axolotl, in particular, serves as a primary model for studying limb regrowth. This process relies on the formation of a blastema—a mass of highly proliferative, undifferentiated cells—which must undergo complex DNA repair, including homologous recombination, to successfully regenerate lost limbs. As of 2024, researchers continue to investigate the driving forces behind the morphological and behavioral diversity seen in complex groups like the tiger salamander.

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