Cnemidophorus Tesselatus Research Articles

Projections of Future Suitable Bioclimatic Conditions of Parthenogenetic Whiptails

This paper highlights the results of bioclimatic-envelope modeling of whiptail lizards belonging to the Aspidoscelis tesselata species group and related species. We utilized five species distribution models (SDM) including Generalized Linear Model, Random Forest, Boosted Regression Tree, Maxent and Multivariate Adaptive Regression Splines to develop the present day distributions of the species based on climate-driven models alone. We then projected future distributions of whiptails using data from four climate models run according to two greenhouse gas concentration scenarios (RCP 4.5 and RCP 8.5). Results of A. tesselata species group suggested that climate change will negatively affect the bioclimatic habitat and distribution of some species, while projecting gains in suitability for others. Furthermore, when the species group was analyzed together, climate projections changed for some species compared to when they were analyzed alone, suggesting significant loss of syntopic areas where suitable climatic conditions for more than two species would persist. In other words, syntopy within members of the species group will be drastically reduced according to future bioclimatic suitability projections in this study.

Morphological Divergence and Genetic Variation in the Triploid Parthenogenetic Teiid Lizard,Aspidoscelis neotesselata

Abstract The parthenogenetic triploid lizard Aspidoscelis neotesselata originated from a hybridization event between a female of diploid parthenogenetic Aspidoscelis tesselata (pattern class C) and a male of Aspidoscelis sexlineata viridis, and A. neotesselata is morphologically more similar to its maternal progenitor, A. tesselata. The geographic distribution of A. neotesselata is characterized by localized arrays of individuals located within a four-county area in southeastern Colorado, and postorigin divergence is visually evident in its four allopatric color pattern classes (A, B, C, and D). A fundamental pattern of morphological divergence was revealed by a multivariate partitioning of its four color pattern classes into two basic groups: an A group (pattern classes A and D) and a B group (pattern classes B and C). A problem introduced by this grouping is the incongruence between the multivariate similarity of pattern classes A and D and the closer geographic proximity of other color pattern classes ...

Comparative Meristic Variability in Whiptail Lizards (Teiidae,Aspidoscelis): Samples of ParthenogeneticA. tesselataVersus Samples of Sexually ReproducingA. sexlineata, A. marmorata, andA. gularis septemvittata

ABSTRACT Is it correct, as is often assumed, that the clonal form of inheritance in parthenogenetic lizards results in less variability than occurs with genetic recombination in their sexually reproducing (gonochoristic) relatives? We tested this hypothesis by comparing morphological variability in samples of parthenogenetic Aspidoscelis tesselata and several gonochoristic species of whiptail lizards. To control for environmental factors that might differentially affect embryonic development of morphological characters, we compared samples obtained from the same or geographically adjacent localities. In addition, we compared apparently “uniclonal” and multiclonal samples from each of two color-pattern classes (C and E) of A. tesselata. For univariate meristic characters, parthenogenetic A. tesselata matched the variability of a sympatric gonochoristic species in 11 of 20 comparisons, had lower variability in six comparisons, and was more variable in three. For multivariate characters derived from principa...

Breadth and Overlap of Diet Between Syntopic Populations of Parthenogenetic Aspidoscelis tesselata C and Gonochoristic Aspidoscelis sexlineata (Squamata: Teiidae) in Southeastern Colorado

Abstract Parthenogenetic Aspidoscelis tesselata (pattern class C) reaches the northern limit of its distribution in Ninemile Valley, Otero County, Colorado. Its coexistence with gonochoristic A. sexlineata permitted comparison of diets between species of different sizes, reproductive modes, and evolutionary histories. Based on numbers of prey in stomachs, A. sexlineata had a broader diet than A. tesselata C in June and July; however, breadth of diets calculated from volumes of prey were nearly the same for the two species. Despite the larger size of A. tesselata C, dietary resources were not partitioned by size and foods present exclusively in one species were rare in its diet. Overlap of diets in June could be explained by chance, but this was not true for July. Remarkably high dietary overlap in July resulted from both species taking advantage of an annual surge in abundance of grasshoppers. There was no evidence that either species was affected adversely by presence of the other.

Pattern-Class D of Parthenogenetic Aspidoscelis tesselata (Sauria: Teiidae) in Las Animas County, Colorado

Abstract The diploid, parthenogenetic, whiptail lizard Aspidoscelis tesselata is represented by two distinctive variants of color pattern in southeastern Colorado. Pattern-class C has been recorded from several sites in the canyonlands of Otero, Las Animas, and Baca counties and D has been recorded from four sites north of the Purgatoire River near Higbee, Otero County. We report a specimen of A. tesselata D collected in 2008 south of the Purgatoire River in Las Animas County, which represents a significant range extension for this distinctive parthenogen.

Reproductive Characteristics of Two Syntopic Whiptail Lizards, Aspidoscelis marmorata and Aspidoscelis tesselata, from the Northern Chihuahuan Desert

We studied reproductive characteristics of two syntopic whiptail lizards, Aspidoscelis marmorata and A. tesselata, inhabiting the northern Chihuahuan Desert. Reproductive characteristics studied were snout–vent length at sexual maturity, size of clutch, and volume of eggs. In A. marmorata, males and females were similar in snout–vent length, but body mass was larger in males than in females. Female A. tesselata were larger in snout-vent length and heavier than female A. marmorata. Mean size of clutch was 3.3 for A. marmorata and 3.5 for A. tesselata. Females of A. marmorata had larger volume of eggs than females of A. tesselata. Data suggest that both A. marmorata and A. tesselata respond to environmental factors of the region in different ways.

Sprint speed and degree of wariness in two populations of whiptail lizards (Aspidoscelis tesselata) (Squamata Teiidae)

Predation is an important selective force that can influence morphology, physiology, behavior, and life-history traits in natural populations. Lizards exhibit a variety of antipredator strategies including flight. Laboratory studies were conducted to determine sprint speed at various body temperatures for juveniles from two populations of the unisexual whiptail lizard Aspidoscelis tesselata. Lizards reared from eggs collected at Terlingua Creek, TC (a site characterized by more abundant vegetation; Big Bend National Park, Texas) exhibited significantly slower sprint speeds regardless of body temperature (25, 30, or 35 °C), as compared to conspecifics from Hot Springs, HS (sparse vegetation). At 30 °C, maximal sprint speed of HS and TC lizards was 46.9 and 38.1 cm/sec, respectively. Field studies were also conducted to assess degree of wariness. Lizards from the HS site ran at a greater approach distance, ran to a greater final distance, and to a greater final total distance than their counterparts of similar size and mass from the TC site. From a total of 186 lizards that were approached at the HS site, 65 (35%) fled to an open area while 121 (65%) stopped running when they found a suitable shelter site under a rock or bush. Similarly, 37 of 92 lizards (40%) stopped running in an open area at the HS site, as compared to 60% that found a shelter site, usually under a shrub or mesquite bush. These results suggest that population differences in sprint speed and wariness may have a genetic basis and result from selection favoring faster sprint speed in animals found in habitats that make them more vulnerable to predation.

DIET OF SYMPATRIC PATTERN CLASSES C AND E OF THE PARTHENOGENETIC WHIPTAIL LIZARD ASPIDOSCELIS TESSELATA AT SUMNER LAKE, DE BACA COUNTY, NEW MEXICO

The diploid checkered whiptail lizard, Aspidoscelis tesselata, is a parthenogenetic species that occupies semiarid habitats in the southwestern USA. It comprises several morphologically distinct pattern classes that occasionally coexist within the same geographical area. Two pattern classes, C and E, coexist on both sides of Sumner Lake and the Pecos River in Sumner Lake State Park, De Baca County, New Mexico. Individuals of pattern class C are larger than individuals of pattern class E (they also produce larger clutches and take longer to reach reproductive maturity). Herein we present analyses of the stomach contents of specimens collected at Sumner Lake to determine if these 2 pattern classes show differences in their diets. Termites made up over 70% of the prey items found in the stomachs of both pattern classes, but when analyzed by volume, the most important prey were cicadas, planthoppers, and short-horned grasshoppers for pattern class C, and short-horned grasshoppers, cicadas, long-horned grasshoppers, termites, and scarab beetles for pattern class E. Considering prey other than termites, pattern class C lizards tended to consume larger prey items than did pattern class E lizards. Aside from this size-related difference, the diet of the 2 pattern classes at Sumner Lake was similar. This lends support to the hypothesis that body size and reproductive differences between the 2 pattern classes are genetically based.

Proximate Causes of a Phylogenetic Constraint on Clutch Size in Parthenogenetic Aspidoscelis Neotesselata (Squamata: Teiidae) and Range Expansion Opportunities Provided by Hybridity

Aspidoscelis neotesselata (Squamata: Teiidae), the triploid, parthenogenetic lizard endemic to southeastern Colorado, originated from a hybridization event involving normally parthenogenetic Aspidoscelis tesselata and bisexual Aspidoscelis sexlineata. A previous study of a sympatric assemblage of these taxa in the Higbee vicinity, Otero County, Colorado, found that A. neotesselata resembled A. tesselata in snout–vent length (SVL) and the much smaller A. sexlineata in clutch size, a pronounced departure from the clutch size predicted from the mean SVL of gravid females. The phylogenetic constraint hypothesis, that clutch size in A. neotesselata is influenced disproportionately by the genome acquired from A. sexlineata, was proposed to explain this enigma. Use of new characters in recently acquired samples of A. tesselata Pattern Class C (N = 44), A. neotesselata Pattern Classes A, B, and C (N = 132), and A. sexlineata (N = 31), revealed that clutch size in A. neotesselata is genetically constrained by both progenitors—a nonadditive component from A. tesselata (large egg volume) and an additive component from A. sexlineata (reduced body volume). Although mean oviductal egg volume, mean SVL for hatchlings of the year, and maximum observed body size were similar in A. neotesselata and A. tesselata, representatives of A. neotesselata attained reproductive maturity at smaller body sizes, and their oviductal eggs were proportionately longer and narrower than those of both progenitor species. Gravid individuals of A. neotesselata were intermediate to those of A. tesselata and A. sexlineata in body volume (BV) and SVL, but, as previously reported, the mean clutch sizes of A. neotesselata and A. sexlineata were similar and significantly smaller than that of A. tesselata. Statistically, egg volume was the least variable of the four primary reproductive attributes investigated. This would presumably ensure the production of hatchlings of adaptive size by each species, a factor that likely supersedes clutch size and body volume in maximizing individual fitness. Hybrid-derived polyploidy (i.e., the addition of an A. sexlineata genome to the diploid genome of A. tesselata) in A. neotesselata and the postformational origin of geographic Pattern Classes A, B, and C, have resulted in a constellation of adaptations that extend well beyond reproductive characteristics. These adaptations have permitted each of the three triploid pattern classes to exploit mutually exclusive habitats, some at a distance of 173 linear kilometers west-northwest of the northern range boundary of A. tesselata in southeastern Colorado.

Evolutionary and Systematic Implications of Skin Histocompatibility Among Parthenogenetic Teiid Lizards: Three Color Pattern Classes of Aspidoscelis dixoni and One of Aspidoscelis tesselata

Abstract The whiptail lizard Aspidoscelis dixoni (Teiidae) comprises three distinctive color pattern classes (i.e., variants); A and B are restricted to Presidio County, Texas, and C is isolated over 500 km to the west-northwest in Hidalgo County, New Mexico. Pattern class E of A. tesselata is widely distributed in Chihuahua, Texas, and New Mexico. Genetic data have verified that these parthenogenetic species are hybrid-derivatives of A. tigris marmorata ♀ X A. gularis septemvittata ♂; however, the number of hybridization events involved in their origin has remained problematic. We used 19 lizards in laboratory skin-grafting experiments to test the histoincompatibility responses among A. dixoni A, B, C, and A. tesselata E. The results of these graft exchanges indicated that individuals of all four pattern classes were mutually histocompatible to skin grafts, a level of genetic homogeneity indicative of the origin of A. dixoni and A. tesselata from the same hybrid lizard. Thus, the color pattern variants A...

Application of the Evolutionary Species Concept to Parthenogenetic Entities: Comparison of Postformational Divergence in Two Clones of Aspidoscelis tesselata and between Aspidoscelis cozumela and Aspidoscelis maslini (Squamata: Teiidae)

Sumner Lake State Park, De Baca County, New Mexico, is the only known locality where three pattern classes of diploid, parthenogenetic Aspidoscelis tesselata (Sumner C, Sumner D, and Sumner E) coexist in syntopy. Reciprocal skin transplants confirmed that the pronounced phenotypic differences between Sumner C and Sumner E represent postformational genetic changes rather than separate hybridization origins. Sumner D is meristically indistinguishable from Sumner C and is considered to be a recent mutational derivative of the latter. In contrast, Sumner E is distinctly different from Sumner C in multivariate meristic characters and several important life-history characteristics. Discordant patterns of phenotypic variation characterize many geographically disjunct groups of A. tesselata classified as pattern class E, thus defying a cohesive diagnosis. Therefore, based on the evolutionary species concept (ESC), we consider Sumner C and Sumner E to be divergent clonal groups in the same species. We contrast this example with a parthenogenetic complex on the Yucatán Peninsula in which formal recognition of Aspidoscelis maslini and Aspidoscelis cozumela can be accommodated under the ESC.

COMPARATIVE ESCAPE BEHAVIOR OF CHIHUAHUAN DESERT PARTHENOGENETIC AND GONOCHORISTIC WHIPTAIL LIZARDS

We characterized differences in escape behavior among syntopic parthenogenetic and gonochoristic whiptail lizards (Teiidae: Aspidoscelis) in western Texas by performing 2 experiments. The first experiment revealed that Aspidoscelis exsanguis (parthenogenetic) allowed a human simulated predator to approach significantly closer than Aspidoscelis neomexicana (parthenogenetic), and both species allowed a significantly closer approach than Aspidoscelis tigris (gonochoristic). Furthermore, A. neomexicana and A. exsanguis did not flee as far as A. tigris, but this difference in flight distance was not statistically significant. Temperature was not correlated with approach distance or flight distance for any of the above species. The second experiment determined that, when captured, Aspidoscelis tesselata (parthenogenetic) was more likely to release cloacal contents on a human captor than A. tigris (gonochoristic).

LIFE HISTORY CHARACTERISTICS SUPPORT SEPARATE ORIGINS OF D-DESIGNATION COLOR PATTERN CLASSES IN PARTHENOGENETIC ASPIDOSCELIS TESSELATA (SQUAMATA: TEIIDAE)

We compared several life history characteristics between 2 syntopic color pattern classes (Conchas C-E and Conchas D) of parthenogenetic Aspidoscelis tesselata from Conchas Lake, New Mexico. These pattern classes lacked significant differences in mean clutch size, mean size of gravid females, SVL frequency distributions of gravid females, and SVL frequency distributions of complete samples. We then compared the Conchas Lake assemblage to the other 2 pattern class assemblages (Higbee, Colorado, and Sumner Lake, New Mexico) whose life history characteristics had been previously reported. Comparisons of life history attributes within and between the 3 assemblages augment morphological and genetic evidence that each population of pattern class D was derived by mutation from individuals of pattern classes C or C-E in different geographic areas.

Hybridization Between Parthenogenetic Lizards (Aspidoscelis neomexicana) and Gonochoristic Lizards (Aspidoscelis sexlineata viridis) in New Mexico: Ecological, Morphological, Cytological, and Molecular Context

Whiptail lizard guilds consisting of different combinations of parthenogenetic Aspidoscelis exsanguis, Aspidoscelis neomexicana, and Aspidoscelis tesselata pattern classes C and D and gonochoristic Aspidoscelis sexlineata viridis inhabit numerous sites in the immediate vicinity of Conchas Lake, San Miguel County, New Mexico. Based on morphological identification by other workers of specimens collected in 1978, A. neomexicana was the species most recently added to the list of whiptail lizards known to occur at Conchas Lake, about 190 km east of its main distribution area in the Rio Grande Valley. We sampled guilds consisting of A. neomexicana and its congeners at Conchas Lake from 2000 through 2003. In 2002 we also collected specimens of what appeared to be another tokogenetic array of A. neomexicana east of the Rio Grande Valley in syntopy with A. tesselata E and A. sexlineata viridis at Fort Sumner, De Baca County, New Mexico. Comparison of karyotypes revealed that individuals of A. tesselata and those assigned by their discoverers to A. neomexicana from Conchas Lake and Fort Sumner have identical diploid karyotypes (2n = 46) that include diagnostic haploid complements of chromosomes derived from independent hybridizations between species in the tigris and sexlineata species groups. Consequently, we used electrophoretic data for 23 gene loci, of which the sMDH, sMDHP, sIDH, ESTD, PEPA, PEPB, ADA, MPI, GPI, and PGM2 loci were definitive, to further validate the hypothesis that the disjunct groups of putative A. neomexicana in eastern New Mexico had been correctly identified. The specimens analyzed electrophoretically also indicated that the Conchas Lake clone of A. neomexicana is identical to the most widely distributed clone of the species in the Rio Grande Valley of New Mexico and that the Fort Sumner clone possessed a distinctive allele.We describe the habitat for A. neomexicana at Conchas Lake at three sites north of the Canadian River and two sites south of the river. Two of the sites north of the Canadian River were studied as examples of guilds that did not include A. sexlineata viridis. The latter species was observed with A. neomexicana, A. tesselata, and A. exsanguis at one site north of the Canadian River and two sites south of the river. At Fort Sumner, we studied A. neomexicana at two sites where it was syntopic with A. tesselata E and A. sexlineata viridis.We identified 15 lizards from three sites at Conchas Lake as hybrids of A. neomexicana × A. sexlineata viridis. Most of these hybrids were found in either patchy or weedy chronically disturbed habitats in which the parental forms were forced into unusually close syntopic relationships. Hybrids between these parental forms were collected in each year from 2000– 2003 and represented a minimum of four and a maximum of five generations.Although hybrids of A. neomexicana × A. sexlineata viridis were characterized by distinctive color patterns, all were rather similar to maternal parent A. neomexicana, but with modifications resulting from the genetic contribution of its paternal parent A. sexlineata viridis. All specimens identified as hybrids by color pattern also possessed meristic characters that distinguished them from both parental forms. Univariate and multivariate analyses of scutellation also revealed evidence of the genetic effects of the parental species on the hybrids.One live hybrid male of A. neomexicana × A. sexlineata viridis was collected at Conchas Lake. The hybrid (American Museum of Natural History R-151739) was a triploid (3n = 69) including the complete diploid complement of A. neomexicana (= A. tigris marmorata × A. inornata) plus a second haploid complement of sexlineata group chromosomes. Karyotypically, in all details this triploid appeared to be an F1 hybrid of A. neomexicana × A. sexlineata viridis. This confirmed hybrid possessed a similar array of color pattern and scutellation characters observed in the other individuals of presumptive

MORPHOLOGICAL CHARACTERISTICS OF A NEWLY DISCOVERED POPULATION OF ASPIDOSCELIS TESSELATA (SQUAMATA: TEIIDAE) FROM CHIHUAHUA, MÉXICO, THE IDENTITY OF AN ASSOCIATED HYBRID, AND A PATTERN OF GEOGRAPHIC VARIATION

Abstract A population of the parthenogenetic teiid lizard, Aspidoscelis tesselata, was recently discovered in the vicinity of Benavides, Chihuahua, Mexico. This population is located in the general area where A. tesselata originated, as a parthenogenetically competent F1 hybrid, from hybridization between A. tigris marmorata and A. gularis septemvittata. Subsequent to its origin, A. tesselata utilized habitats associated with the Rio Grande and Pecos River drainages to expand its range into New Mexico. We used a canonical variate analysis of samples from Chihuahua, Mexico, and the Rio Grande and Pecos River distribution corridors in southern New Mexico to determine the pattern of morphological variation among the 4 populations. The 2 populations from New Mexico were divergent, both from the Chihuahuan populations (which were morphologically similar) and from each other. A male specimen, collected with A. tesselata in the Benavides vicinity, was identified as a putative A. tesselata × A. tigris marmorata h...

Congruent Patterns of Genetic and Morphological Variation in the Parthenogenetic Lizard Aspidoscelis tesselata (Squamata: Teiidae) and the Origins of Color Pattern Classes and Genotypic Clones in Eastern New Mexico

Aspidoscelis tesselata exhibits significant clonal diversity despite its recent origin (from hybridization between A. tigris marmorata and A. gularis septemvittata) and its parthenogenetic mode of reproduction. Two hypotheses have been advanced to explain the derivation of its genetic and morphological variation: (1) separate parthenogenetic lineages derived from several different F1 hybrid zygotes, and (2) postformational mutations occurring in a parthenogenetic lineage derived from a single F1 hybrid zygote. We evaluated these competing hypotheses with evidence from skin transplant studies, protein electrophoresis, multivariate analyses of morphological characters, and geographic distributions of pertinent groups. Starting with the clonal diversity at Conchas Lake State Park, San Miguel County, New Mexico, we expanded the study to include populations at Sumner Lake State Park and Fort Sumner (De Baca County), Puerto de Luna (Guadalupe County), and Arroyo del Macho and Roswell (Chaves County). This enabled us to resolve origins of color pattern classes and genotypic clones in eastern New Mexico. We used pattern class designations C-E and E-C to signify that elements of both pattern classes were expressed in populations at Conchas Lake and Arroyo del Macho.The two pattern classes at Conchas Lake (C-E and D) had the same F1 hybrid karyotype (2n = 46), with haploid sets of 23 chromosomes characteristic of each progenitor species of A. tesselata. Clonal variation was found at 4 of the 35 gene loci examined electrophoretically: GPI (glucose-6-phosphate isomerase), EST2 (a muscle esterase), sACOH (aconitase hydratase), and MPI (mannose-6-phosphate isomerase). The strong congruence between genotype and morphological variation facilitated the characterization of three morphological subgroups of C-E. Although these subgroups lacked individually distinctive color patterns, they were discriminated effectively in canonical variate analyses based on scalation characters and a priori groups of known genotype.Nine individuals of Conchas C-E and four individuals of Conchas D have histocompatibility data from a recent skin transplant study (Cordes and Walker, 2003). The subgroup identities of the C-E specimens document histocompatibility among the three morphological subgroups of C-E and between each subgroup and representatives of pattern class D. This evidence, together with Maslin's (1967) report of histocompatibility between pattern classes C and E, suggests that all color pattern classes, morphological subgroups, and genotypic clones of A. tesselata can be traced back to a single ancestral F1 hybrid zygote.A pair of pale broken lines in the middorsal region distinguishes pattern class D from the other pattern classes. However, Conchas ID shared the GPI −100/−96, EST2 100/96 genotype with Conchas IC-E, and individuals of these pattern classes were very similar in multivariate meristic characters. Sumner D expressed the same type of relationship, resembling the syntopic population of Sumner C rather than the other population of D. In addition, certain individuals of Sumner C had partially divided (D-like) vertebral lines—additional evidence that Sumner C was ancestral to Sumner D. We conclude that pattern class New Mexico D is polyphyletic, having originated twice from different individuals of C-E and C in the vicinities of Conchas and Sumner Lakes.The northern position of pattern classes C and C-E in the range of A. tesselata is consistent with recent colonizations by individuals from more southerly populations. A candidate source population, based on its extensive color pattern and meristic variation, is E-C at Arroyo del Macho. The strong morphological resemblance of several northern populations to Macho E-C rather than to either syntopic clones or geographically proximate populations of other pattern classes supports this possibility. Evidence from geographic distributions, patterns of genotypic and meristic variation, and histocompati

CAN PARTHENOGENETIC CNEMIDOPHORUS TESSELATUS (SAURIA: TEIIDAE) OCCASIONALLY PRODUCE OFFSPRING MARKEDLY DIFFERENT FROM THE MOTHER?

Parthenogenetic reproduction has not precluded the genesis of extensive genetic variation in the whiptail lizard, Cnemidophorus tesselatus. In Conchas Lake State Park, San Miguel County, New Mexico, the population of C. tesselatus includes pattern class C, with 4 allozyme variants, and pattern class D, with 3 allozyme variants. In 1988, we obtained a lizard in the park, described herein, with a unique color pattern and unusual meristic characters, which indicate that occasional females of C. tesselatus continue to be capable of producing neonates phenotypically different from the mother.

Skin Histocompatibility between Syntopic Pattern Classes C and D of Parthenogenetic Cnemidophorus tesselatus in New Mexico

At Conchas Lake State Park, San Miguel County, New Mexico, four allozymic variants of parthenogenetic Cnemidophorus tesselatus pattern class C and three allozymic variants of C. tesselatus D are syntopic with one gonochoristic and two parthenogenetic congeners. Our study of 14 individuals revealed that C. tesselatus C and D from this site are histoincompatible with both their maternal, Cnemidophorus tigris marmoratus, and paternal, Cnemidophorus gularis septemvittatus, progenitors. Evidence of skin histocompatibility between these combinations of C. tesselatus pattern class C and D lizards supports the hypothesis of a single hybrid origin for representatives of this species at the study site.

Natural Hybridization Between the Teiid Lizards Cnemidophorus tesselatus (Parthenogenetic) and C. tigris marmoratus (Bisexual): Assessment of Evolutionary Alternatives

Annual hybridization is taking place between representatives of the parthenogenetic lizard Cnemidophorus tesselatus (2n = 46, 47) and males of the bisexual species C. tigris marmoratus (2n = 46) in desert grassland habitats at Arroyo del Macho, Chaves County, New Mexico. This raises the question of whether a new triploid parthenogenetic species may be originating as a consequence of this activity. Hybrids were collected in each of four years (1996–1999), and 20 of 21 hybrids collected (12 males and 8 females) were available for study. Although a triploid parthenogenetic species (Cnemidophorus exsanguis 3n = 69) and a diploid bisexual species (C. inornatus 2n = 46) were also found at the hybridization site, the genealogy of the hybrids was determined unequivocally with karyotypic and electrophoretic evidence (34 loci tested). The specimens examined electrophoretically included an adult female and one of her laboratory-reared daughters, which demonstrated for the first time clonal inheritance in C. tesselatus pattern class E.The population of C. tesselatus at Arroyo del Macho is characterized by two karyotypic cytotypes. The ancestral one (2n = 46) occurs at about half the frequency of the derived cytotype (2n = 47), which apparently was produced by centric fission of the ancestral X-chromosome from C. tigris In contrast, the occurrence of the two cytotypes was reversed and strongly asymmetrical in the hybrids; only one of nine hybrids possessed the fissioned X-chromosome. This individual was significantly different in 12 meristic characters from the sample of hybrids with intact X-chromosomes. Predictably, principal components scores for this individual fell outside the 95% confidence ellipse of scores of the other eight hybrids that were karyotyped. The skewed ratio and multiple phenotypic differences suggest that hybrids inheriting a fissioned X-chromosome might be at a selective disadvantage compared to hybrids with intact X-chromosomes.All 20 hybrids closely resemble C. tesselatus in most color pattern features. However, these hybrids, like C. tigris marmoratus lack lateral stripes. Because the population of C. tesselatus at Arroyo del Macho has lateral stripes (or their remnants), hybrids can be readily distinguished from C. tesselatus by this color pattern feature. Compared to the two parental species, hybrids had a significantly lower mean number of scales around midbody, but hybrids resembled either C. tesselatus or C. tigris marmoratus in other univariate meristic characters. This mosaic pattern of resemblance was simplified to a three-dimensional depiction of variation using principal components analysis. Each of two principal components expressed the resemblance of hybrids to one of the two parental species. A third component reflected the difference between hybrids and both parental species. A canonical variate analysis of meristic characters demonstrated the multivariate distinctiveness of each group—hybrids, C. tesselatus and C. tigris marmoratus However, based on Mahalanobis D2 distances, the closest morphological resemblance among hybrids and parental species was between hybrids and the maternal species, C. tesselatusNine additional museum specimens, suspected of being C. tesselatus × C. tigris marmoratus hybrids, were identified, as such, by a canonical variate analysis using our samples of C. tesselatus, C. tigris marmoratus and hybrids from Arroyo del Macho as a priori groups. These nine individuals document hybridizations between C. tesselatus and C. tigris marmoratus at two additional localities in Chaves County, New Mexico, two localities in Sierra County, New Mexico, and a cluster of sites near Presidio, Presidio County, Texas. Previously, several of these hybrids had been misidentified as male C. tesselatusThe reproductive systems of female and male hybrids were compared histologically to those of C. tesselatus and C. tigris marmoratus respectively. Sexually mature and reproductive adults of C. tesselatu

Reproductive Characteristics and Body Size in the Parthenogenetic Teiid Lizard Cnemidophorus tesselatus: Comparison of Sympatric Color Pattern Classes C and E in De Baca County, New Mexico

Cnemidophorus tesselatus is an allodiploid, parthenogenetic lizard comprised of a number of distinctive tokogenetic arrays (Frost and Hillis, 1990) presently identified by four color pattern class descriptors: C, Colorado D, New Mexico D, and E (Taylor et al., 1996; Walker et al., 1997). The macrogeographic relationships of these pattern classes were outlined in Zweifel's (1965) pioneering study of geographic variation in Cnemidophorus tesselatus. Pattern class C was known to exist isolated from the other pattern classes in parts of southeastern Colorado, northwestern Oklahoma, and northwestern Texas. Sympatry between pattern classes C and D was known to occur only in the vicinities of the historic townsite of Higbee, Otero County, Colorado, and Conchas Lake, San Miguel County, New Mexico. Pattern class E occurred to the south, with specimens from Fort Sumner, De Baca County, New Mexico, approximately 105 km south of the Conchas Lake locality, documenting the closest proximity of pattern class E to pattern classes C and D.