HERPETOLOGY OF ZUNI MOUNTAINS — GEHLBACH 319 



genetic currents" are purely speculative, they are in accord with 

 paleoecological and neoecological evidence. It is significant that 

 the north-south patterns of Pleistocene clunatic change and local 

 physiographic differentiation augment each other in affecting dispersal. 



If cool-moist intervals limited the northward movement of wide- 

 spread, grassland species, they were equally potent in restricting 

 desert and desert-grassland forms like Crotalus atrox. No great 

 changes in drainage pattern have occurred on the Colorado Plateau 

 since the late Pliocene (Hunt, 1956, p. 85), but the Rio Grande valley 

 of southern New Mexico did not exist as a lowland pathway for 

 north-south dispersal prior to early mid-Pleistocene time (Ruhe, 

 1960). Are some species that reach their northern limits in the 

 Zuni region, therefore, postglacial invaders? Dowhng (1956) accounted 

 for the presence of similar xerically adapted species in Arkansas by 

 postulating recent immigration from the Great Plains during a 

 Holocene arid interval. 



What about the distribution of such vagile forms as Amby stoma 

 tigrinum and Thamnophis elegarts? It seems possible that at least 

 some of them remained locally at lower elevations on the Colorado 

 Plateau during the Pleistocene cHmatic shifts. This is suggested by 

 Tihen's description (1942) of neotenic A. tigrinum in Great Plains 

 glacial deposits and typical metamorphosed individuals in interglacial 

 sediments. Many of the other widespread species are equally 

 adaptable and some hke Phrynosoma douglassi, in addition to A. 

 tigrinum and T. elegans, are relatively abundant in both Montane 

 and Plains Life Belts. 



Summary 



Between 1951 and 1961, the systematics, ecology, and life history 

 of 30 species of amphibians and reptiles were studied in the Zuni 

 Mountains region, McKinley and Valencia Counties, New Mexico. 

 This area, characterized by extremes of temperature and midsummer 

 rainfall, contains Plains, Roughlands, and Montane Life Belts, and 

 extensive lava flows. Elevations range from 5794 feet at Laguna on 

 the eastern end of the study area to 11,389 feet at the top of Mount 

 Ta3^1or. Unfortunately, man has drastically altered natural environ- 

 ments. Drought pervades the recent climatic history of the region. 



Of 19 common species, no two have the same vertical distribution 

 or relative abundance. Five lizards of similar adult size have different 

 morphological and physiological adaptations and occupy different 

 habitats. In the Iguanidae, scansorial species such as Urosaurus 

 ornatus have more lamellae than terrestrial species like Phrynosoma 

 douglassi. Oviposition in Holbrookia maculata, Sceloporus undulatus, 

 Sceloporus graciosus, and U. ornatus seems to be correlated with 



