Genic and Morphological Differentiation in Mexican Pseudoeurycea (Caudata: Plethodontidae), with a Description of a New Species Author(s): James F. Lynch, David B. Wake and Suh Y. Yang Source: Copeia, Vol. 1983, No. 4 (Dec. 14, 1983), pp. 884-894 Published by: American Society of Ichthyologists and Herpetologists (ASIH) Stable URL: http://www.jstor.org/stable/1445090 Accessed: 28-01-2016 00:13 UTC REFERENCES Linked references are available on JSTOR for this article: http://www.jstor.org/stable/1445090?seq=1&cid=pdf-reference#references_tab_contents You may need to log in to JSTOR to access the linked references. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://www.jstor.org/page/ info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Allen Press and American Society of Ichthyologists and Herpetologists (ASIH) are collaborating with JSTOR to digitize, preserve and extend access to Copeia. http://www.jstor.org This content downloaded from 136.152.142.102 on Thu, 28 Jan 2016 00:13:21 UTC All use subject to JSTOR Terms and Conditions Copeia, 1983(4), pp. 884-894 Genic and Morphological Differentiation in Mexican Pseudoeurycea(Caudata: Plethodontidae), with a Description of a New Species JAMES F. LYNCH, DAVID B. WAKE AND SUH Y. YANG A new species of pseudoeurycea from the Transverse Volcanic Range of south- central Mexico is shown to be electrophoretically and morphologically distinct from P. leprosa, P. robertsi and P. altamontana. Pseudoeurycea robertsi and P. altamontana, although previously placed in different species groups, are shown to be closely similar genetically. Pseudoeurycea leprosa, the most widely distrib- uted of the species that were studied, comprises a central "core" group of rela- tively undifferentiated populations, and a series of peripheral isolates that are genetically well-differentiated from one another and from the central group. THE 23 recognized species of the pletho- METHODS dontid salamander genus Pseudoeuryceaare widely distributed in humid montane areas of Electrophoresis.-Horizontal starch gel electro- Mexico and Guatemala (Wake and Lynch, 1976). phoresis was used to analyze variation in sam- Although these salamanders are the most abun- ples from 7 populations currently referred to dant vertebrates in many upland habitats, their P. leprosa, and one population each of P. alta- ecology is virtually unstudied. In addition, the montana, P. robertsi, and a previously unde- systematics of the genus is only imperfectly scribed species (Table 1). understood, for the dearth of taxonomically Salamanders were collected in 1975-1976, useful morphological characters has made it dif- and were shipped alive to Berkeley, where they ficult to identify stable groupings of closely re- were killed by immersion in dilute chloretone. lated species. In a previous paper (Lynch et al., Samples of liver, kidney, spleen, stomach, heart 1977) we employed multivariate morphometry and skeletal muscle were removed. Tissue ex- and starch gel electrophoresis to compare P. tracts that were not used at once were stored smithi, a well-known Oaxacan species, and P. at -70 C. Mixed tissue extracts were subjected unguidentis, an enigmatic sympatric form that to horizontal starch gel electrophoresis. We were earlier had been reduced to synonymy with P. able to consistently score 18 presumptive ge- smithi (Bogert, 1967). The results of our mor- netic loci. The enzymes, their abbreviations, and phological and genetic comparisons agreed in the appropriate gel/buffer systems (Selander et indicating that P. unguidentis is a valid, well- al., 1971) are given in Table 2. Nei's (1972) differentiated species. genetic distance (DN) and Rogers' (1972) ge- The present study applies similar methods to netic distance (DR) were calculated for each a group of populations of Pseudoeuryceathat in- pairwise combination of the seven populations habits the Transverse Volcanic Range (Cordil- of P. leprosa and the new species, and for one lera Volcanica) of south-central Mexico. The population of P. leprosa versus the new species, study began as a comparison of isolated popu- P. altamontana, and P. robertsi(Tables 3, 4). lations of P. leprosa; we later included two near- by species whose systematic status was poorly Morphometric methods.-Discriminant function understood, and the work received added im- analysis was employed to test the hypothesis that petus when our electrophoretic comparisons re- the four species of Pseudoeurycea, despite ob- vealed the presence of an undescribed species vious similarities in size and overall body form, of Pseudoeurycea.A continuing goal is to clarify can be reliably distinguished on the basis of con- the discrepancies between earlier attempts to ventional external measurements and tooth delimit species groups within the genus (Taylor, counts. A related question is the extent of in- 1944; Baird, 1951; Wake and Lynch, 1976) and traspecific, as opposed to interspecific, morpho- a recent immunological study (Maxson and logical differentiation in Pseudoeurycea.Because Wake, 1981) that indicated a radically different the fragmented geographic range of P. leprosa grouping of species. greatly exceeds the combined distributions of ? 1983 by the American Society of Ichthyologists and Herpetologists This content downloaded from 136.152.142.102 on Thu, 28 Jan 2016 00:13:21 UTC All use subject to JSTOR Terms and Conditions LYNCH ET AL.-MEXICAN PSEUDOEURYCEAVARIATION 885 TABLE 1. LOCALITY INFORMATION FOR SAMPLES OF PseudoeuryceaUSED IN THE ELECTROPHORETIC ANALYSIS. Sample Elevation number Species Locality (m) 1 P. leprosa 6 km W Rio Frio, Mexico 2 P. leprosa La Malinche, 10 km N Canoa, Puebla 3,000 3 P. leprosa 12 km N Tlaxco, Puebla 2,900 4 P. leprosa Xometla, Veracruz 2,600 5 P. leprosa San Bernardino, Puebla 2,500 6 P. leprosa 12-14 km SW Las Vigas, Veracruz 2,950 7 P. leprosa ZempoalaDistrict, 10 km N Tres Cumbres,Morelos 2,770 8 P. longicauda 23 km W Villa Victoria, Mexico 2,840-2,970 9 P. robertsi Nevado de Toluca, 4 km N Raices, Mexico 3,320 10 P. altamontana ZempoalaDistrict, 20 km N Tres Cumbres, Morelos 3,130 the other three species, it is of interest to com- Formalin, and stored in 70% ethanol. The fol- pare the level of morphological divergence lowing 8 characters were considered (see Lynch among isolated populations of P. leprosa to the et al., 1977, for detailed description of the mea- divergence between these populations and P. surements): head width, head length, fore limb altamontana, P. robertsi, and the undescribed length, hind limb length, body length, tail Pseudoeurycea.The SPSS computer program for length, combined number of maxillary and pre- stepwise discriminant function analysis was used maxillary teeth, and number of anterior vo- to generate discriminate functions, scores, and merine teeth. Because previous studies had in- an a posteriori classification matrix for 134 sal- dicated the existence of marked ontogenetic amanders assigned a priori to five populations changes in body proportions (Lynch et al., 1977) of P. leprosa, and one population each of P. analysis was restricted to post-juveniles (com- altamontana, P. robertsi, and the undescribed bined head and body length >40 mm). We con- Pseudoeurycea. sidered only individuals that possessed an intact All measurements were made on salamanders tail, and rejected specimens that were contorted that had been killed by immersion in dilute clor- or mutilated in such a way that accurate mea- etone solution, fixed in 10% neutral buffered surement was impaired. It would have been TABLE 2. ENZYMES, THEIR ABBREVIATIONS AND BUFFER SYSTEMS USED IN THE ELECTROPHORETIC ANALYSIS. Voltage and Enzyme Abbreviation(s) of loci Buffer time run phosphogluconatedehydrogenase Pgd Tris maleate with 100 V (3.5 h) NADP in gel peptidase (1-leucyl-alanine) Pept-1, Pept-2 Li 300 V (3 h) glutamate-oxaloacetate-transaminate Got-1, Got-2 mannose phosphate isomerase Mpi indophenol oxidase Ipo (from Mpi stain) \ Tris citrate II 100 V (3.5 h) isocitrate dehydrogenase Icd-1, Icd-2 sorbitol dehydrogenase Sordh leucine aminopeptidase Lap malate dehydrogenase Mdh-1, Mdh-2 Tris citrate IV 180 V (3 h) phosphate isomerase Gpi phosphoglucomutase Pgm-1, Pgm-2 lactate dehydrogenase Ldh-1, Ldh-2 Poulik 200 V (3 h) This content downloaded from 136.152.142.102 on Thu, 28 Jan 2016 00:13:21 UTC All use subject to JSTOR Terms and Conditions 886 COPEIA, 1983, NO. 4 TABLE3. ALLOZYMEFREQUENCIES AT 18 Loci IN Pseudoeurycealeprosa (LOCALITIES1-7) ANDP. longicauda (LOCALITY 8). The most rapidly migrating band is indicated as "a." Numbered localities are identified in Table 1. Sample sizes are in parentheses. Locality 1 2 3 4 5 6 7 8 Locus (21) (21) (5) (28) (3) (9) (20) (20) Mpi c (.95) c c a (.05) c b (.78) c e (.78) d (.05) c (.91) c (.22) f(.22) d (.04) Ipo b b b b a (.83) b b b (.17) Icd-1 a a a a (.93) a (.33) a a (.63) b c (.07) c (.67) c (.37) Icd-2 a a c a a a (.78) a b c (.22) Sordh a (.88) a e a (.39) a (.67) a (.67) a (.75) e e (.12) b (.15) b (.17) b (.33) d (.25) c (.04) e (.16) e (.42) Pgd c (.95) b (.02) c c c b(.5) c c d (.05) c (.98) c (.5) Gpi b (.86) b b a (.12) a b b a (.37) c (.14) b (.88) b (.63) Pgm-l a a a a a a a a