New Species of Plethodon 15 



The 18 samples cluster into 4 groups, each representing a taxonomic 

 species. There is very little geographic genetic variation within P. teyaha- 

 lee, but there is a considerable amount in both P. glutinosus and P. 

 aureolus. Indeed, some samples within both of the latter species are as 

 different genetically as are some comparisons of P. teyahalee and P. 

 jordani. The southwestern populations oi P. jordani from the Unicoi and 

 Nantahala Mountains are genetically very similar to P. teyahalee (Pea- 

 body 1978); in fact, these two species are more closely related than any 

 other two species of Plethodon yet examined (see Highton and Larson 

 1979). It is therefore not surprising that they hybridize so extensively 

 (Highton 1970). 



Plethodon jordani is the most variable species (mean //=.21), P. 

 aureolus (mean H-.\2) and P. glutinosus (mean H-. 1 1) are intermediate, 

 while P. teyahalee (mean H=.01) is the least variable. Compared to more 

 northern populations of P. glutinosus and P. jordani (Highton and Mac- 

 Gregor 1983), these southern samples are much more variable. The P. 

 glutinosus, however, have slightly lower average H values than Arkansas 

 and Oklahoma P. glutinosus (Duncan and Highton 1979). 



In light of my unpublished evidence that P. aureolus and P. jordani 

 hybridize at localities 46-48 on Sassafras Ridge (the only known area of 

 contact between the two species), the proper taxonomic relationship 

 between the two forms is difficult to decide. The average D of the 8 

 comparisons between the two forms (.3 1 ) is not very different from that of 

 the 28 comparisons between P. aureolus and P. glutinosus (.29) or the 20 

 comparisons between P. aureolus and P. teyahalee (.43), two species with 

 which P. aureolus is sympatric and is not known to hybridize. In the 

 southwestern isolates of P. jordani (in the Great Smoky Mountains, 

 Cowee Bald, the Nantahala Mountains, Cheoah Bald, and in the Unicoi 

 Mountains), P. jordani is always a high altitude species, whereas P. aureo- 

 lus is mostly a lower altitude form. The color pattern is very different 

 (except in the northern Unicoi Mountains where hybridization between 

 the two has occurred). None of the above mentioned populations of nearby 

 P. jordani has as abundant lateral and dorsal yellow, white or brassy 

 spotting. Plethodon aureolus is not significantly more similar genetically 

 to adjacent samples of Unicoi Mountain P. jordani than it is to other 

 populations of P. jordani throughout its range (Peabody 1978). The only 

 similarity between P. jordani and P. aureolus is that they are both smaller 

 than Appalachian populations of P. glutinosus and P. teyahalee. I there- 

 fore regard the interbreeding between the two on Sassafras Ridge as a case 

 of hybridization between species rather than intergradation between con- 

 specific populations. Considering the very extensive hybridization between 

 P. jordani and P. teyahalee throughout their contact zone in the Unicoi 

 Mountains, it is curious that P. teyahalee does not appear to hybridize with 

 the hybrid populations of P. aureolus and P. jordani on Sassafras Ridge. 



