Unisexuals? Say what?

One of the most frequent questions I get asked is to what is meant by "hybrid" or "polyploid" salamanders in Michigan. These salamanders are often similar in appearance to the Blue-spotted Salamanders, but have several diagnostic characters which set them apart. Unisexual hybrids usually have longer toes, a more elongate dorsum, and a more pointed nose than a true Ambsytoma laterale.

Blue-spotted Salamander, Ambystoma laterale, Photographed in Clare County, Michigan

Unisexual Hybrid Salamander, Ambystoma sp., Photographed in Oakland County, Michigan

Unisexual hybrids can be diploid, triploid, or even tetraploid. These animals share the genotypes of the Blue-Spotted, Jefferson's, Smallmouth, and occasionally Eastern Tiger Salamander. These unisexually female salamanders migrate to breeding pools with other salamanders on warm, rainy spring nights where they utilize sperm from males of other Ambystoma species to fertilize their eggs. The sperm of the males stimulates unreduced eggs to develop, resulting in clones of the female, this is a process known as kleptogenesis. It is also possible for the genome to be replaced or for the number of chromosomes in the offspring to be increased. The genetics of these salamanders is still undergoing study by many researchers.