Identification

Many of the unisexual Ambystoma are nearly morphologically indistinguishable from the diploid, sexual species from which their genomes are derived or appear intermediate between these species. These salamanders exist in female-only populations.

Ecology and Conservation

Unisexual Ambystoma spend much of their lives underground, emerging only en masse during migrations to breeding ponds. They typically lay their eggs in temporary, forested wetlands, where there must exist at least one other member of the genus Ambystoma (see Taxonomy for more details).

Distribution

These salamanders occur throughout much of the northern half of Indiana and must always be found alongside at least one other species of Ambystoma.

Taxonomy

Unisexual salamanders of the genus Ambystoma are a remarkable evolutionary oddity. Populations of these salamanders consist of females only, and they reproduce through a unique strategy called "kleptogenesis". In kleptogenesis, females use the sperm of congeneric salamanders to initiate egg production. They typically do not incorporate any genetic material from this sperm into their offspring, producing clones of themselves. However, they occasionally incorporate the haploid genome of these sperm, either replacing one of the haploid genomes already present or adding to the genome, increasing the ploidy of the offspring. As a result, these salamanders occur in a variety of forms varying in ploidy and which diploid, sexual species have and continue to "donate" sperm. These diploid species contributing to the nuclear genomes of unisexual Ambystoma include A. laterale, A. jeffersonianum, A. texanum, and A. tigrinum.

During the time scientists have unraveled this mystery, these salamanders have had a muddled taxonomic history. Today, they are rarely referred to with a Latin binomial and are typically described collectively as "unisexual Ambystoma" or by initials of the species contributing to each of their (sometimes many) haploid genomes (e.g., LJJ or LLJ).

Literature Cited