Ambystoma laterale

Ambystoma jeffersonianum and A. laterale comprise a complex that includes pure bisexual diploid populations and populations that may be represented by bisexual diploid individuals, female hybrids with several different combinations of parental chromosomes (including diploids, triploids, tetraploids, and pentaploids), and/or rare male hybrids. Up to at least five different chromosomal combinations have been found at a single site.

In response to the nomenclatural difficulties presented by this complex, an informal system of indicating ploidy and chromosomal makeup has been recommended (Bogart and Klemens 1997). For example, the "LLLJ" designation (or "A. (3) laterale-jeffersonianum") indicates a tetraploid salamander with three sets of laterale chromosomes and one set of jeffersonianum chromosomes. For convenience, all populations including pure laterale (LL) and laterale-dominated genomes (e.g., LLJ) might be included in the species A. laterale (e.g., Klemens 1993).

However, biological complexities confound such a simple treatment. Polyploid hybrid individuals in the complex may produce offspring with diverse chromosomal makeup. For example, an LLJ female can produce offspring that do not have laterale-dominated genomes (e.g., LJJ). And single clutches have been documented with both diploid and triploid embryos. It is even possible for a triploid hybrid to produce pure diploid offspring (e.g., LL or JJ).

Truly intermediate hybrids with equal chromosomal representation (i.e., LJ, LLJJ) are uncommon and are but two of many possible outcomes of hybridization. In New England and New York, hybrids are more common than are the bisexual species, but bisexuals usually (or are presumed to) exist in low numbers in populations composed mostly of hybrids (Bogart and Klemens 1997). Thus, for example, a pond with triploid LLJ should also have at least some LL.

Hybrid populations are maintained by breeding between a hybrid female and a male of one of the diploid bisexual species, and the hybrid offspring are the result of gynogenetic or hybridogenetic reproduction (Bogart and Klemens 1997). In gynogenetic reproduction, male sperm stimulates egg development, but the male genome is not incorporated into the zygote. In hybridogenetic reproduction, the male genome is incorporated, "but upon maturity of the offspring, the paternal genome is eliminated in a meiotic or pre-meiotic event while the rest of the hybrid's genome is passed on to future generations, usually in an altered state" (Bogart and Klemens 1997).

Thus, recent work on hybrid phenomena in these salamanders indicates that the species names "A. platineum" (= LJJ) or "A. tremblayi" (= LLJ) formerly used for the A. jeffersonianum-A. laterale hybrids are inappropriate because LJJ and LLJ are not strictly gynogenetic triploid lineages. Consequently, a recent checklist (Crother et al. 2000) did not recognize either A. platineum or A. tremblayi as valid species.

To accommodate the genetic variation in these salamanders (and the often uncertain genetic composition of particular populations), we have established for this database the following elements: (1) Ambystoma jeffersonianum (Jefferson Salamander), used for pure populations only; (2) Ambystoma laterale (Blue-spotted salamander), used for pure populations only; (3) Ambystoma hybrid pop. 1 (jeffersonianum x laterale; jeffersonianum genome dominates), used for hybrid populations dominated by the jeffersonianum genome (e.g., populations that include mainly LJJ individuals); this element includes "Ambystoma platineum"; (4) Ambystoma hybrid pop. 2 (jeffersonianum x laterale; laterale genome dominates), used for hybrid populations dominated by the laterale genome (e.g., populations that include mainly LLJ individuals); this element includes "Ambystoma tremblayi"; (5) Ambystoma pop. 3 (jeffersonianum/laterale complex - uncertain composition), used for populations for which chromosomal representation is unknown. If needed we could establish additional elements for hybrid populations that involve A. laterale, A. texanum, and/or A. tigrinum.

See Kraus (1985), Bogart and Licht (1987), Bogart et al. (1987), Kraus et al. (1991), Lowcock et al. (1991), and Bogart and Klemens (1997) for information on the involvement of A. jeffersonianum in hybridization with A. texanum, A. tigrinum, and/or A. laterale. See Lowcock et al. (1987) and Bogart and Klemens (1997) for discussions of nomenclatural treatment of hybrid populations.

See Kraus (1988), Shaffer et al. (1991), and Jones et al. (1993) for phylogenetic analyses of North American Ambystoma.

Southeastern Quebec to Lake Winnipeg, south through Great Lakes region and New England to northern Indiana and New Jersey. Several apparently disjunct populations occur around the periphery of the range (e.g., see Brownlie [1988] for Nova Scotia record). Hybridizes with A. jeffersonianum over a large area south of this range. See Nyman et al. (1988) for distribution in New Jersey.

Number of occurrences of pure A. laterale is uncertain, but there are many.

Biggest threat is loss and degradation of habitat as a result of coversion to agricultural and urban use. Roads negatively impact salamander abundance in roadside habitat (deMaynadier and Hunter 2000). Increased acid deposition is a potential threat.