25 



buted throughout the clearing, indicating an invasion of this species 

 in the absence of a stable population of _C. uniparens . It is concluded 

 that perhaps direct competition is a critical factor in this situation 

 after all. 



6*. — . 1981. Long-term analysis of reproductive periodicity in the 

 lizard Cnemidophorus uniparens . AMER. MIDLAND NAT. 105(1): 93-101. 



Reproductive cycles were monitored in captives for their entire 

 lives. The annual cycle of a short reproductive period followed by a 

 long non-reproductive period persisted indefinitely in 80% of the ani- 

 mals. The cycle was reduced to 5 months in the absence of environmen- 

 tal cues. The number of clutches laid per individual remained rela- 

 tively constant, suggesting that it, like the reproductive rhythm, is 

 under endogenous control. There is evidence for multiple clutches dur- 

 ing the reproductive period in nature, followed by a long refractory 

 period. The refractory periods progressively shorten in captivity un- 

 til they become indistinguishable from between-clutch intervals, imply- 

 ing environmental control of the refractory period. Sexual behavior 

 between captive individuals of parthenogenetic Cnemidophorus reported 

 by Crews and Fitzgerald (1980) is discussed, and evidence suggests that 

 it is abnormal behavior associated with captivity. 



65. — . and C. O. McKinney. 1976. Natural hybridization between 

 parthenogenetic and bisexual lizards: detection of uniparental source 

 by skin grafting. JOURNAL OF EXPERIMENTAL ZOOLOGY 1 96(3): 3^1-350. 



Skin grafting and electrophoresis was done to determine the paren- 

 tal species of suspected natural hybrids in Cnemidophorus . Six species 

 ( exsanguis, inornatus, neomexicanus, tesselatus, tigris and uniparens ) 

 were sympatric in an area ^0' by 200' dominated by weedy vegetation 

 along the railroad right-of-way 3 miles south of San Antonio, Socorro 

 County, New Mexico. A stable creosotebush community existed on one side 

 of the area and agricultural lands on the other. _C. inornatus occurred 

 in very high densities in the area as did the unisexual species, result- 

 ing in increased chances for hybridization. _C. tigris was characteris- 

 tic of the creosote community and rare in the hybrid zone. 50% of the 

 neomexicanus exhibited the characteristic bite marks inflicted during 

 copulation in Cnemidophorus . The hybrid specimens (2 inornatus X uni- 

 parens and 3 inornatus X neomexicanus ) were superficially morphological- 

 ly similar to the unisexual parent but possessed bluish undersides. 

 Known hybrids in the genus are reviewed; 25 are males, 7 are females and 

 ^ were not sexed. Skin grafting is suggested as a technique for deter- 

 mining parental species. 



66. — . and C. Smart. 1977. Analysis of histo-incompatibility in a 



