HERPETOLOGY OF ZUNI MOUNTAINS — GEHLBACH 255 



Vertical Distribution 



In comparison with the Guadalupe Mountains, a region of about 

 equal size and vertical range in southeastern New Mexico, it is evident 

 that Zuni environmental diversity exceeds the diversity of the Zuni 

 herpetofauna. Only 7 (33 percent) of 21 Zuni genera contain more 

 than one species whereas 17 (41 percent) of 42 genera in the Guada- 

 lupes have two or more species (Gehlbach, in ms.). Sixty-five am- 

 phibians and reptiles currently are recorded in the Guadalupe region; 

 only 30 definitely are known in the Zunis. This relative paucity may 

 be influenced directly by the high elevations and climatic extremes. 

 With increasing elevation there is a decline in the number of species 

 (fig. 3) . Such forms as Scaphiopus homhijrons, Eumeces obsoletus, and 

 Crotalus molossus, near the boundary of their range in the Zunis, are 

 restricted locally in contrast to their greater vertical distributions 

 elsewhere. 



Vertical transects from Thoreau, McEanley County, south to 

 Cottonwood Gulch, thence to Lookout Mountain and El Morro, 

 Valencia County (7000-9100 feet), and from Grants to Mount Taylor, 

 Valencia County (6400-11,389 feet), were repeated in several sum- 

 mers (fig. 1). These, the locality records, and miscellaneous observa- 

 tions demonstrate that no two morphologically related species have 

 precisely the same vertical range or relative abundance (fig. 3) . This 

 displacement pattern is especially apparent within genera but also 

 occurs between genera if species possess similar habits (e.g., between 

 Holbrookia maculata and Phrytiosoma douglassi, or between Masticophis 

 taeniatus and Pituophis melanoleucus) . Axtell (1959, table 1) and 

 Lowe and Zweifel (1952, fig. 4) have diagramed similar patterns in 

 west Texas and central New Mexico respectively. The probability 

 that two species will not be equally efficient in the same environment 

 has been discussed by many biologists (e.g., Lack, 1949; Hutchinson, 

 1957). 



Ecological differences were observed most readily among the Zuni 

 lizards (table 2). Since similar differences have been correlated with 

 morphological variation (Collette, 1961; Lundelius, 1957) and thermo- 

 regulation (Bogert, 1949; Fitch, 1956b), the presence or absence of 

 such correlations may help to elucidate local ecological segi'egation. 

 Sceloporus undulaius, S. graciosus, Urosaurus ornatus, Phrynosoma 

 douglassi, Eumeces multivirgatus, and Cnemidophorus velox are of 

 similar size; hence, presumably they are able to capture similar-sized 

 prey. Attention is focused on these species with particular reference 

 to the number of lamellae as an index to climbing ability (Collette, 

 1961). 



Of the iguanids, U. ornatus shows the greatest climbing propensities 

 and has the most lamellae in proportion to size (cf. table 2; fig. 4). 



