Ecological patterns of body-size and clutch-size variation in the parthenogenetic teiid lizard Cnemidophorus tesselatus

Pattern class C of parthenogenetic Cnemidophorus tesselatus reaches its sou thern range limit at Sumner Lake State Park, De Baca County, New Mexico, wh ere it is syntopic at several sites with a northern population of pattern c lass E of the same species. Samples collected at Sumner Lake in 1997 confir med significant differences between the two pattern classes in body length and clutch size initially observed in samples collected in 1995 and 1996. I n contrast, these characteristics were non-significantly different in patte rn classes C and Colorado D, sympatric (and marginally syntopic) at sites n ear the historic town-site of Higbee, Otero County, Colorado. The differenc e between each pair of sympatric pattern classes is based on different mean body sizes and a positive relationship between clutch size and body size i n C, tesselatus. A comparison of 10 samples of three color pattern classes of C. tesselatus, spanning approximately 1100 km of latitudinal range, reve aled that the small clutch size characterizing pattern class E at Sumner La ke was found in other populations of pattern class E and in one population of pattern class C as well. Similarly, the larger clutch size of pattern cl ass C at Sumner Lake was found in die Higbee population of pattern class C and in some populations of pattern class E. Therefore, despite constraints on variability predicted from a parthenogenetic reproductive mode, reproduc tive characteristics are remarkably variable both within and between patter n classes. In the absence of conclusive evidence of more than one hybridiza tion event in the origin of C. tesselatus and the geographic proximity of o nly pattern class E to the progenitor species, we hypothesize, from color p attern and meristic evidence, that pattern class C was most likely derived from one or more E-like individuals, and that pattern classes New Mexico D and Colorado D were derived from individuals of pattern class C. Mutations could also have modified reproductive characteristics permitting C. tessela tus to expand its distribution beyond that available to a general-purpose g enotype derived from the progenitor species C. tigris marmoratus and C. gul aris septemvittatus and expressed in pattern class E. In addition to its ex tensive geographic range; the ecological success of C. tesselatus can be ga uged by the fact that nine of our 10 samples of C. tesselatus were from pop ulations sympatric with 1-3 sexual species and 1-2 parthenogenetic species of Cnemidophorus.