Sympatric Occurrence of Two Species of the Two-Lined Salamander (Eurycea bislineata) Complex

Genetic analyses of contact zones between closely related taxa are critical to an understanding of reproductive isolation between species. We evaluated allelic frequencies and external morphology from one such contact zone between two members of the Eurycea bislineata complex (i.e., E. cirrigera and E. wilderae). We found that, within this zone of contact, these presumed species had significantly different frequencies of alleles at three loci. In addition, these sympatric forms were significantly different in lateral mottling pattern, tail color, and length of tail stripe. These morphological patterns were identical to those used to describe the original subspecies E. b. cirrigera and E. b. wilderae. Evidence from this zone of contact supports the hypothesis that these forms are separate species. Moreover, there is evidence of ecological and/or reproductive character displacement among these species when in sympatry.

Fig. 1.

Eurycea cirrigera and E. wilderae from Nancytown Creek, Habersham County, Georgia in zone of sympatry. For E. cirrigera (A), note the row of distinct light-colored spots along the side and the long tail stripe. For E. wilderae (B), note the absence of light spots on the side and the short tail stripe

Fig. 2.

The relationship between body and tail color for sympatric (A) and allopatric (B) populations of Eurycea cirrigera and E. wilderae. Open squares represent E. cirrigera, whereas black squares represent E. wilderae. The color scale (i.e., 0 to 18) corresponds to a color chart ranging from brown to red (see text for explanation)

Fig. 3.

The frequency distribution of female SVL (in millimeters) for sympatric and allopatric Eurycea cirrigera and E. wilderae populations. Solid bars = E. wilderae, open bars = E. cirrigera. (A) sympatric populations from Nancytown Creek, Habersham County, Georgia (E. cirrigera, n = 27; E. wilderae, n = 26). The sympatric data are from the combined 1997 and 1998 samples. (B) allopatric populations of E. cirrigera (n = 58, from Poplar Cove Spring, Lafayette County, Mississippi; Marshall, 1997) and E. wilderae (n = 42, from Station Creek, Macon County, North Carolina; Bruce, 1988:table 6)