Reproductive Characteristics of Two Syntopic Whiptail Lizards, Aspidoscelis Marmorata and Aspidoscelis Tesselata, From the Northern Chihuahuan Desert (Notes) (Report‪)‬

Reproduction in some species of the genus Aspidoscelis from North America (Schall, 1978; Vitt and Breitenbach, 1993), and specifically from the Pacific coast of Mexico (Ramirez-Bautista et al., 2000; Ramirez-Bautista and Pardo-de la Rosa, 2002; Mata-Silva and Ramirez-Bautista, 2005), have been studied. Reproductive strategies of Aspidoscelis from temperate zones are different than those of tropical environments (Vitt and Breitenbach, 1993). Populations studied from temperate zones generally reproduce May-August (Anderson and Karasov, 1988). In contrast, in tropical species, activity and reproductive seasons are extended and often are continuous if conditions are favorable (e.g., A. communis, Ramirez-Bautista and Pardo-de la Rosa, 2002; A. lineatissima, Ramirez-Bautista et al., 2000; A. ocellifer, Vitt, 1983). Frequency of clutches in this genus appears to be associated with length of reproductive season in species from high latitude (Burkholder and Walker, 1973) or high elevations (Stevens, 1983). Species from temperate zones produce 1 clutch/year, whereas some tropical species produce [greater than or equal to] 3 clutches/year (e.g., A. ocellifer; Vitt, 1983), except in species from tropical dry forest, where just one clutch is produced (A. communis; Ramirez-Bautista and Pardo-de la Rosa, 2002; A. lineatissima; Ramirez-Bautista et al., 2000). Size and relative mass of clutch of most species studied from temperate and tropical environment are small compared to wait-ambush species (Vitt and Breitenbach, 1993). At this time, most species studied did not show a clear relationship between size of clutch and snout-vent length; species of Aspidoscelis share most of the characteristics mentioned. Aspidoscelis marmorata is a medium-sized, bisexual species commonly found in different habitats of the Chihuahuan Desert, ranging from southern New Mexico and western Texas to northern Mexico (Behler and King, 1979). In contrast, A. tesselata, a unisexual and morphologically diverse species, occurs from southern Colorado through New Mexico and Trans-Pecos Texas into northern Chihuahua, Mexico (Zweifel, 1965; Walker et al., 1997). However, little is known about the reproductive biology of A. tesselata, and no study has been conducted on A. marmorata and A. tesselata in their shared geographic range (Schall, 1978).