Extreme variant of the triploid parthenogenetic lizard Aspidoscelis exsanguis (Squamata: Teiidae) from New Mexico.
This collaboration began with sharing of digital images (Fig. 1) of the unusual lizard by GCC to LKK, who forwarded them to JMW, and the latter to JEC, for opinions on its identity. After JMW indicated that the lizard is highly distinctive, one of a kind, and should be reported in the literature, GCC sent it to the Museum of Southwestern Biology (MSB), University of New Mexico, for cataloging as number MSB 94825. The specific point of the discovery in Bosque Farms was on a residential gravel driveway near an open ditch surrounded in part by patches of habitat suitable for whiptail lizards, along with horse and hay pastures, situated approximately 200 m east of the Rio Grande (34[degrees] 51' 56.4624"N, 106[degrees] 430 4.9506"W, datum WGS84, elev. ~1,486 m).
JMW measured both the snout-vent length (SVL) and tail length to the nearest millimeter. A description of the dorsal color pattern was prepared using terminology for longitudinal pale stripes and intervening dark fields recommended by Burt (1931), Duellman and Zweifel (1962), and Walker et al. (2009). Terminology and data for meristic characters analyzed, based on Duellman and Zweifel (1962), Manning et al. (2005), and Walker et al. (2009), in the specimen and in comparative material of A. neomexicana from Hidalgo County, southwestern New Mexico, and A. exsanguis from De Baca County, east-central New Mexico, collected by JEC, are included in Table 1. The objective of this report was to provide data for the identification of specimen MSB 94825 within the context of the distinguishing characters of the species present in Bosque Farms rather than statistical analyses of their variation, per se. Thus, it was not considered to be either necessary or justifiable to collect large samples of these two species from the fragmented habitat in the area, which explains our use of available representative samples from Hidalgo and De Baca counties. Nevertheless, data for several characters in A. exsanguis from many sites in the southwestern United States, made available to us by the review provided by H. L. Taylor (HLT), contributed to the morphological comparisons.
The qualitative scutellation characters examined in all specimens included sizes of the postantebrachial scales on the posterior aspect of each forearm and of the mesoptychial scales bordering the edge of the gular fold, anterior extent of the circumorbital scale series on both sides of the head, and number of parietal scales on the posterior aspect of the head (see Duellman and Zweifel, 1962). Analyses of meristic variables (Table 1) were performed using JMP software (Version 10; SAS Institute, Inc., Cary, North Carolina, 2012) to generate a mean [+ or -] 1 SE and the range of variation for each character examined in A. neomexicana and A. exsanguis. Alternative software was used by HLT to generate these data for specimens examined by him.
Following capture of the lizard (i.e., MSB 94825) in August 2013, it was inferred to be in the third summer of life having grown to a SVL of 83 mm and a mass of 16 g. Based on studies of southwestern whiptail lizards (e.g., Manning et al., 2005; Walker et al., 2012), the lizard was hatched in the late summer of 2011, either grew to adult size or nearly so in the summer of 2012, and became of reproductive size in the spring-summer of 2013. It has a TL of 144 mm, of which 91 mm is regenerated posterior to the 37th row of caudal scales. The lizard has a group of enlarged to moderately enlarged postantebrachial scales, abruptly enlarged mesoptychial scales bordering the gular fold, circumorbital series anteriorly on each side only bordering the separation between the third and fourth supraocular scales, and five rather than three parietals. These character states, and the SVL of >80 mm, indicate that it is not an aberrantly patterned individual of A. neomexicana, the most-abundant teiid species observed in Bosque Farms, which has granular postantebrachials, small mesoptychials, either complete or nearly complete circumorbital series, three parietal scales, and maximum SVL of <80 mm. Most of the attributes noted for MSB 94825 are similar to those observed in samples of A. exsanguis from various areas of New Mexico; only A. exsanguis among congeners known from Valencia County (Degenhardt et al., 2005) possesses enlarged postantebrachial scales such as those noted in the specimen. Nevertheless, in most individuals of this species examined by JMW those scales were proportionally larger than in MSB 94825.
Analysis of meristic variables in MSB 94825 for comparisons to data for samples of A. neomexicana and A. exsanguis revealed that the count of dorsal granules between the paravertebral stripes at midbody could not be obtained because of lack of definition of the paravertebral stripes anterior to a 10-mm area near the base of the tail (Fig. 1-Upper; Table 1). The analyses also revealed an aberrant lack of development in the interlabial scales anterior to one enlarged scale on each side. Comparison of meristic data for the specimen with samples of A. neomexicana from Hidalgo County and A. exsanguis from De Baca County revealed that they fall within the ranges of variation of only the lateral supraocular granules character in A. neomexicana and the circumorbital scales and lateral supraocular granules in A. exsanguis (Table 1). Except for the low count of dorsal granules from the occipital scales to the first row of caudal scales for the specimen (Table 1), data for the counts of scales around midbody from one lateral row of ventral scales to opposite row of laterals, femoral pores combined, and subdigital lamellae characters are only one or two scales below the ranges for the sample of A. exsanguis. Thus, it was convenient to compare data for the specimen to variation within a large, pooled sample of A. exsanguis from numerous sites over its range provided in the review by HLT. This revealed the presence of additional specimens of A. exsanguis with lower scores for the dorsal granules around midbody (35 of 398, 8.8% between 60-67), femoral pores (22 of 403, 5.5% between 28-32), and subdigital lamellae (69 of 410, 16.8% between 27-29) than recorded for MSB 94825. According to HLT, "... the coincidence of low-end counts for granules around midbody, femoral pores, and subdigital lamellar would be unexpected in the same individual (e.g., MSB 94825), but it can occur. Of 387 individuals [of A. exsanguis examined by him], five had combinations of granules around midbody <68, femoral pores <33, and subdigital lamellae <30." Thus, of the meristic variables for which data are available, only the dorsal granules from the occipital scales to the first row of caudal scales and interlabial scales characters in MSB 94825 differ from all other specimens of A. exsanguis examined by JMW: these two characters were not assessed for specimens examined by HLT.
The typical adult dorsal color pattern of A. exsanguis, based on >350 specimens examined by JMW from Arizona, New Mexico, Texas, and the Mexican state of Chihuahua, initially includes a gray-brown to brown-black ground color arranged as longitudinal fields between six pale, colored stripes arranged in three pairs (Fig. 2). On each side of the body (ventral to dorsal) there are lateral, dorsolateral, and paravertebral stripes with the latter being unevenly margined in most specimens. The fields on each side of the body are lower lateral (ventral to lateral stripe), upper lateral (dorsal to lateral stripe), dorsolateral (dorsal to dorsolateral stripe), and vertebral (dorsal to paravertebral stripe). Certain of the stripes extend onto the proximal fourth of the tail. In addition, the dorsum is profusely spotted (Fig. 2), both in the fields and on the stripes. Ontogenetic changes accompanying growth to larger adult sizes typically include partial to complete loss of stripe definition posteriorly until there is a partially striped but profusely spotted dorsum.
In MSB 94825, the tail is essentially uniformly brown and unstriped. Wide, hazy, gray-tan lateral and dorsolateral stripes are present on each side of the body, but there are no discrete spots in the lower lateral, upper lateral, and dorsolateral fields, all of which are dark brown. The paravertebral stripes are visible as such only on the last 10 mm of the body near the base of the tail, anterior to which there is a wide, gray-tan band the entire length of the vertebral field (Fig. 1-Upper). There is only the slightest indication that that this band comprises the much-expanded paravertebral stripes that would be apparent in typically patterned A. exsanguis. Ventrally, the specimen is blue-white (Fig. 1-Lower).
Because neither of the widespread gonochoristic whiptail species (i.e., A. inornata, little striped whiptail and A. marmorata, marbled whiptail) known from western New Mexico have been observed by GCC and ALF in Bosque Farms, the possibility that MSB 94825 is a tetraploid hybrid of A. exsanguis x A. inornata as reported from Alamogordo, Otero County, by Neaves (1971) can be discounted. In addition, the specimen does not have the striped and spotted dorsal pattern that characterized the hybrid of these species reported by Neaves (1971). Analyses of qualitative characters of scutellation, meristic variables (Table 1), color pattern (Figs. 1 and 2), and SVL also discounted the possibility that MSB 94825 is an extreme variant of A. neomexicana, which does occur in Bosque Farms in abundance.
The only logical inference is that the specimen is an extreme variant of A. exsanguis which has only recently been observed in Bosque Farms (i. e., 2013 and 2014). However, the specimen does not resemble the species in color pattern (Fig. 1-Upper vs. Fig. 2), and it is atypical of the species in scutellation characters (e.g., size of postantebrachial scales and number of parietal scales) and meristic variables (e.g., lower dorsal granules from the occipital scales to the first row of caudal scales , dorsal granules between the paravertebral stripes at midbody [no count], interlabial scales [no count]). Other examples of extreme dorsal color pattern variants of parthenogenetic species have been reported in A. neomexicana (Dessauer and Cole, 1989), A. tesselata (Walker and Cordes, 2003), and Aspidoscelis neotesselata (Taylor et al., 2006). Although, as in the present case, the causation of the extreme variation in each species could not be determined, it seems that only two possible explanations exist. Either MSB 94825 is the product of a nongenetic developmental anomaly, from which normally patterned offspring would be expected (see Dessauer and Cole, 1989), or it is the result of one or more mutations from which the aberrant pattern could possibly be perpetuated in future generations.
This study was facilitated by the assistance of J. Noble and T. Giermakowski, University of New Mexico, in the process of having the specimen catalogued into the MSB collection of amphibians and reptiles. Gratitude is also expressed for the Spanish Resumen which was prepared by J. A. Lemos-Espinal at our request. This contribution was materially enhanced by the constructive criticisms offered by C. J. Cole and H. L. Taylor.
Burt, C. E. 1931. A study of the teiid lizards of the genus Cnemidophorus with special reference to their phylogenetic relationships. Bulletin of the United States National Museum 154:1-286.
Degenhardt, W. G., C. W. Painter, and A. H. Price. 2005. Amphibians and reptiles of New Mexico. University of New Mexico Press, Albuquerque, New Mexico.
Dessauer, H. C., and C. J. Cole. 1989. Diversity between and within nominal forms of unisexual teiid lizards. Pages 49-71 in Evolution and ecology of unisexual vertebrates (R. M. Dawley and J. P. Bogart, editors). New York State Museum Bulletin 466, Albany, New York.
Duellman, W. E., and R. G. Zweifel. 1962. A synopsis of the lizards of the sexlineatus group (genus Cnemidophorus). Bulletin of the American Museum of Natural History 123:155-210.
Manning, G. J., C. J. Cole, H. C. Dessauer, andJ. M. Walker. 2005. Hybridization between parthenogenetic lizards (Aspidoscelis neomexicana) and gonochoristic lizards (Aspidoscelis sexlineata viridis) in New Mexico: ecological, morphological, cytological, and molecular context. American Museum Novitates 3492:1-56.
Neaves, W. B. 1971. Tetraploidy in a hybrid lizard of the genus Cnemidophorus (Teiidae). Breviora 381:1-25.
Taylor, H. L., R. J. Rondeau, and J. Sovell. 2006. Alternative ontogenetic pathways to color pattern class B in a newly discovered population of parthenogenetic Aspidoscelis neotesselata (Squamata: Teiidae). Herpetological Review 37:40-44.
Walker, J. M., and J. E. Cordes. 2003. Can parthenogenetic Cnemidophorus tesselatus (Sauria: Teiidae) occasionally produce offspring markedly different from the mother? Southwestern Naturalist 48:126-129.
Walker, J. M., J. E. Cordes, H. L. Taylor, and G. J. Manning. 2012. Aspidoscelis tesselata common checkered whiptail, northern life history. Herpetological Review 43:479-480.
Walker, J. M, J. R. Dixon, R. W. Axtell, and J. E. Cordes. 2009. The taxonomic status of the inornate (unstriped) and ornate (striped) whiptail lizards (Aspidoscelis inornata [Baird]) from Coahuila and Nuevo Leton. Herpetological Review 40:276-282.
Submitted 16 October 2013.
Acceptance recommended by Associate Editor, Neil B. Ford, 19 June 2014.
James M. Walker, * Geoffrey C. Carpenter, Austin L. Fitzgerald, Larry K. Kamees, and James E. Cordes
Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701 (JMW, LKK)
1695 Smith Place, Bosque Farms, NM 87068 (GCC)
Museum of Southwestern Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM 87131 (ALF)
Division of Sciences and Mathematics, Louisiana State University Eunice, Eunice, LA 70535 (JEC)
* Correspondent: email@example.com
Table 1--Summary of meristic characters for samples of Aspidoscelis neomexicana from Hidalgo County, New Mexico, and A. exsanguis from De Baca County, New Mexico, in the University of Arkansas Department of Zoology collection as compared with specimen MSB 94825 from Valencia County in the Museum of Southwestern Biology collection. Data for the two species are mean-SE (first row) and range and (n) (second row); included for the specimen is either a single datum for analyzable characters or NC for no count possible' for a character. Character A. neomexicana 94825 A. exsanguis "GAB" Scales 80.7 [+ or -] 0.44 68 73.3 [+ or -] 0.27 around midbody 75-83 (24) 70-75 (26) from one lateral row of ventral scales to opposite row of laterals "OR" Dorsal 207.9 [+ or -] 1.52 159 181.9 [+ or -] 0.64 granules from the 193-220 (24) 176-190 (26) occipital scales to the first row of caudal scales "PV" Dorsal 11.6 [+ or -] 0.15 NC 4.7 [+ or -] 0.13 granules between 11-13 (24) 4-6 (26) the paravertebral stripes at midbody Femoral pores 40.8 [+ or -] 0.31 33 36.0 [+ or -] 0.24 summed from both 38-43 (24) 34-38 (26) sides of body Subdigital 34.3 [+ or -] 0.20 30 32.0 [+ or -] 0.19 lamellae of the 33-36 (24) 31-34 (26) fourth toe of the left pes Circumorbital 24.0 [+ or -] 0.32 8 8.0 [+ or -] 0.26 scales, summed 20-26 (24) 6-11 (26) from both sides of body Lateral 43.8 [+ or -] 1.11 30 29.2 [+ or -] 0.77 supraocular 30-55 (24) 23-40 (26) granules, summed from both sides of body Interlabial 35.4 [+ or -] 0.90 NC 24.0 [+ or -] 0.93 scales, summed 29-46 (24) 14-33 (26) from both sides of body
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|Author:||Walker, James M.; Carpenter, Geoffrey C.; Fitzgerald, Austin L.; Kamees, Larry K.; Cordes, James E.|
|Date:||Sep 1, 2014|
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