Fig. 1. Gila Monster (Heloderma suspectum) photographed on 5 August 2019, Rincon Mountains, at an elevation of 2,089 m.
R E S E A R C H  A R T I C L E
Origin of an Arizona Population of the New Mexico Whiptail Lizard Like all known unisexual 
(Aspidoscelis neomexicanus): Evidence from Skin Grafting and Review of whiptails, A. 
an Enigmatic Specimen neomexicanus 
Trevor B. Persons, Colorado Plateau Research Station, Northern Arizona University, Flagstaff, AZ; trevor.persons@nau.edu reproduces 
John W. Wright (deceased), Natural History Museum of Los Angeles County, Los Angeles, CA through par-
Steve W. Gotte, Department of Vertebrate Zoology, National Museum of Natural History, Suitland, MD; gottes@si.edu thenogen-
Aspidoscelis neomexicanus (New Mexico Whiptail; et al. (2002) in using the genus name Aspidoscelis rath- esis, whereby 
Fig. 1) is a diploid unisexual (all-female) lizard species er than Cnemidophorus for North American whiptails, females lay un-
that arose through hybridization between Aspidoscelis and we use the specific name neomexicanus rather than 
marmoratus (Marbled Whiptail; = Aspidoscelis tigris neomexicana following the explanation by Tucker et al. fertilized eggs 
marmoratus of Wright 1993) and Aspidoscelis inorna- (2016) of why the genus name Aspidoscelis should be that hatch into 
tus (Little Striped Whiptail; Lowe and Wright 1966, considered masculine.
Brown and Wright 1979, Cole et al. 1988, Densmore Aspidoscelis neomexicanus is native to the Rio more females, 
et al. 1989, Wright 1993). Like all known unisexual Grande Valley in New Mexico and western Texas, in- all of which 
whiptails, A. neomexicanus reproduces through parthe- cluding some adjacent closed basins in southern New 
nogenesis, whereby females lay unfertilized eggs that Mexico (Axtell 1966, Wright 1971, Cole et al. 1988, are genetically 
hatch into more females, all of which are genetically Degenhardt et al. 1996; Fig. 2). Leuck et al. (1981) identical to 
identical to their mothers (e.g., Persons and Wright reported a disjunct population at Conchas Lake, San 
2009). One consequence of parthenogenesis is that Miguel County, New Mexico, in the Canadian River their mothers 
new populations can be founded by single individu- drainage, which they interpreted as likely resulting (e.g., Persons 
als, increasing the chances that accidental introduc- from human introduction. However, Walker et al. 
tions will result in established populations. Aspidoscelis (1992) challenged this assertion, suggesting that the and Wright 
neomexicanus is an evolutionarily young species, its population at Conchas Lake may in fact be native. 2009). 
origin postdating the subspecific radiation of A. tigris Subsequently, additional populations of A. neomexi-
(Tiger Whiptail) sensu lato (Brown and Wright 1979, canus were discovered in eastern New Mexico, near 
Densmore et al. 1989). In this paper we follow Reeder Fort Sumner in De Baca and Roosevelt counties in 
Copyright © Notice: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-N D 4.0) SONORAN HERPETOLOGIST 34 (3) 2021 70
Outside of New 
Mexico and 
western Texas 
Aspidoscelis 
neomexica-
nus has been 
Fig. 1. Aspidoscelis neomexicanus from near the Puerco River at Petrified Forest National Park, Apache Co., Arizona (LACM 147015). reported from 
Photo by T.B. Persons.
the Pecos River drainage (Taylor 2002, Cordes et al. location. The original location is adjacent to the Puerco Petrified Forest 
2011).  While the existence of multiple, disjunct popu- Ruins visitor site, which includes bathroom facilities, National Park, 
lations may indicate a more widespread native distribu- and an associated pump house and small sewage pond 
tion, both Conchas Lake (site of a popular state park) are located across (west of ) the main park road, in Apache Co., Ari-
and Fort Sumner (along roads and railway lines) are the area inhabited by A. neomexicanus. Maintenance zona (Persons 
logical places where A. neomexicanus could conceiv- activities (driving into A. neomexicanus habitat, load-
ably be accidentally or intentionally introduced. A ing and unloading construction materials, etc.) could and Wright 
range extension reported from southwest of Carrizozo provide a means for lizards to hitchhike to the park’s 1999a, Emmons 
in Lincoln County, New Mexico (Burkett et al. 2004) south entrance developed area. Livo et al. (2019) in-
may represent a natural extension of its distribution voked a similar scenario involving “vehicular rafting” et al. 2015) 
north along the Tularosa Valley from the Rio Grande on military equipment moved between an armory and in the 
Valley near Las Cruces and El Paso.
Outside of New Mexico and western Texas vicinity of Salt 
Aspidoscelis neomexicanus has been reported from Lake City, Utah 
Petrified Forest National Park, Arizona (Persons and 
Wright 1999a, Emmons et al. 2015) and in the vicin- (Oliver and 
ity of Salt Lake City, Utah (Oliver and Wright 2007), Wright 2007), 
and populations in both of these areas are presumed 
to have originated from human introductions. Fig. 2 and popula-
includes all reported locations for A. neomexicanus, na- tions in both of 
tive and introduced. At Petrified Forest, A. neomexica-
nus was first discovered in 1998 along the Puerco River these areas are 
west of the main park road, Apache Co. (Persons and presumed to 
Wright 1999a). Then, in 2010, it was found near the 
developed area at the south park entrance, Navajo Co., have originated 
ca. 26 km (16 mi.) south of the original Puerco River from human 
site (Emmons et al. 2015). Intensive herpetofaunal 
surveys in this southern area beginning in 1997 and introductions. 
continued pitfall trap monitoring since (Drost et al. 
2001, Emmons et at. 2015), without detections of A. 
neomexicanus prior to 2010, suggest that the southern 
population is recently established. While an indepen- Fig. 2. Approximate distribution of Aspidoscelis neomexicanus. 
dent introduction from the native range of the species Solid yellow shading indicates presumed native range, and 
in New Mexico (e.g., from a park visitor or delivery dots in Utah and Arizona represent presumably introduced 
of goods from Albuquerque) is possible, perhaps more populations near Salt Lake City and Petrified Forest National Park. Disjunct populations in eastern New Mexico may also be 
likely is inadvertent transport from the Puerco River introduced (see text).
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and a training site to possibly explain the introduc- Mexico (Cuellar 1977); and between a population in 
tion of unisexual Aspidoscelis neotesselatus (Colorado Texas, at the southern edge of the range of the species, 
Checkered Whiptail) near Denver, Colorado. Tamarisk and the possibly introduced population at Conchas 
control activities in the Puerco River floodplain could Lake in northeastern New Mexico (Cordes et al. 
also conceivably provide opportunities for inadvertent 1990). Histoincompatibility (as expressed by rejection 
transport of A. neomexicanus to other areas of the park. of skin grafts between individuals) can occur among 
As with the original park inventory of Drost et al. unisexual whiptails of the same species due to postfor-
(2001), recent surveys in areas of the park between the mational mutations at histocompatibility loci (Cole et 
Puerco River and Rainbow Forest have failed to detect al. 2019) and is thus not necessarily an indication of 
A. neomexicanus (Andy Bridges, pers. comm.). Thus, separate hybrid origin. However, histocompatibility (as Although 
the existence of the recently discovered southern popu- expressed by acceptance of skin grafts) strongly sug-
lation is unlikely to be the result of natural expansion gests the same hybrid origin (Cuellar 1977, Cuellar presumably 
from the Puerco River location. and Wright 1992). introduced, we 
Genetic Origin of the Arizona Population as Methods initially consid-
Revealed Through Skin Grafting ered the pos-
In 1998 we collected two individuals of A. neomexi-
Although presumably introduced, we initially canus from the newly discovered population near the sibility that the 
considered the possibility that the population of A. Puerco River, Petrified Forest National Park, Apache population of A. 
neomexicanus at Petrified Forest arose through a sepa- County, Arizona, now preserved as specimens at the 
rate hybridization between A. tigris and A. inornatus. Natural History Museum of Los Angeles County neomexicanus 
While apparently isolated populations of A. inornatus (LACM 162343-4; cross-cataloged with the National at Petrified 
occur at Petrified Forest (Persons and Wright 1999b), Park Service as PEFO 15283 and 15276), and two 
A. tigris is not known from the immediate vicinity of individuals from within the native range of the species Forest arose 
the park (Drost et al. 2001). However, A. tigris does along the Rio Puerco at US Highway 66, Bernalillo through a sepa-
occur elsewhere in the Little Colorado River Basin, County, New Mexico (LACM 162345-6). We also 
including near Winslow to the west, which has a di- collected two individuals of Aspidoscelis velox (Plateau rate hybridiza-
rect connection to Petrified Forest via the Puerco and Striped Whiptail), to be used as a source of xenografts tion between 
Little Colorado Rivers, and, at the time, we did not for all four A. neomexicanus.  These were collected 
know the distributional extent of the newly discovered in 1998 at Mormon Crossing of West Chevelon A. tigris and 
population of A. neomexicanus. Although A. tigris and Creek, Sitgreaves National Forest, Coconino Co., A. inornatus. 
A. marmoratus are currently regarded as separate spe- Arizona (LACM 162349) and at San Francisco Wash, 
cies (e.g., Crother 2017), a hypothetical parthenogen Coconino National Forest, Coconino County, Arizona While appar-
derived from hybridization between A. tigris and A. (LACM 162350). Lizards were permanently marked ently isolated 
inornatus in Arizona would likely appear similar to A. by toe-clipping.
neomexicanus. Surgical procedures were performed on 7 December populations of 
Shortly after discovery in Arizona we initiated a 1998 at the BioScience Annex at Northern Arizona A. inornatus oc-
skin grafting study to attempt to confirm our suspicion University. Lizards were anesthetized with an intra-
that A. neomexicanus from Petrified Forest was conspe- peritoneal injection of Ketamine Hydrochloride at a cur at Petrified 
cific with lizards from within its native range in New dosage of 0.2 mg/gram lizard body weight.  Circular Forest (Persons 
Mexico. Studies have shown A. neomexicanus to be pieces of skin, 3 mm in diameter, were excised using a 
genetically uniform throughout its range, using protein Miltex disposable biopsy punch. Grafts were removed and Wright 
electrophoresis (Parker and Selander 1984, Cole et al. from the paravertebral light stripes on the lizard’s dor- 1999b), A. tigris 
1988), mitochondrial DNA (Brown and Wright 1979, sal surface, and when returned were rotated 90 degrees 
Densmore et al. 1989), and histocompatibility (Cuellar so that the light stripes within the grafts were perpen- is not known 
1977) analyses. In parthenogenetic Aspidoscelis, accep- dicular to the paravertebral light stripes, facilitating from the imme-
tance of skin grafts between individuals demonstrates graft recognition (e.g., Cuellar 1977, Cuellar and 
that they are histocompatible, and are therefore likely Wright 1992, Abuhteba et al. 2000). Grafts were care- diate vicinity of 
isogenetic (Cuellar 1977, Cuellar and Wright 1992). fully positioned with forceps and sealed with New Skin the park (Drost 
Isogenicity suggests that individuals are derived from liquid bandage. Lizards were housed in clean 10-gal-
a common ancestor, i.e., the same original hybrid-de- lon aquaria without water, food, or substrate for 48 et al. 2001). 
rived parthenogenetic female (Cuellar 1977, Cordes et hours to minimize risk of grafts becoming dislodged.  
al. 1990, Abuhteba et al. 2000). Maslin (1967) dem- Thereafter lizards were given water, sand substrate, and 
onstrated that A. neomexicanus will reject skin grafts folded paper towels for cover. Lizards were fed com-
from another species, Aspidoscelis tesselatus, and there- mercially available crickets and mealworms, and given 
fore does exhibit an immune response. Skin grafting water ad libidum. Aquaria were housed in the offices 
has been used previously to demonstrate isogenicity of the Colorado Plateau Research Station at Northern 
in A. neomexicanus from throughout its range in New Arizona University. Evaluation of grafts were made ev-
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ery few days for the duration of the study. The experi- Discussion
ment was terminated on 14 June 1999, after 189 days. 
At termination lizards were sacrificed, fixed in 10% That six of eight grafts exchanged between indi-
formalin and preserved in 70% ethanol, and deposited vidual A. neomexicanus from Petrified Forest and New 
in the herpetology collection of the Natural History Mexico were accepted, with at least one graft accepted 
Museum of Los Angeles County (above). on all four lizards, indicates that lizards from the two 
populations are histocompatible, and therefore likely That six of 
Results genetically identical (Cuellar 1977). This result elimi- eight grafts 
nates the possibility that the Petrified Forest popula-
Each of the four A. neomexicanus received five skin tion arose through a separate hybridization between A. exchanged 
grafts, as follows. One autograft, as a control (graft re- tigris and A. inornatus. These results indicate that the between 
moved, rotated, and replaced on the same individual); Petrified Forest population either represents a range 
one intrapopulational allograft (between each indi- extension of the native Rio Grande Valley distribution individual A. 
vidual from the same population); two interpopula- or is the result of an introduction. Introduction is sup- neomexicanus 
tional allografts (between individuals from the Petrified ported by the fact that the Petrified Forest population 
Forest and New Mexico populations); and one xeno- is separated by ca. 240 km (149 mi.) from the nearest from Petrified 
graft from A. velox to test for presence of an immune known population in the Rio Grande Valley of New Forest and New 
response. Results of the experiment are shown in Fig. Mexico, and this separation includes ca. 95 km (59 
3. Six of the eight interpopulational allografts (three mi.) of unsuitable habitat straddling the continental Mexico were ac-
of four from each pair of lizards) between individuals divide (Persons and Wright, 1999a). In addition, there cepted, with at 
from Petrified Forest and New Mexico were perma- are numerous plausible scenarios to explain an intro-
nently accepted. In addition, all four autografts were duction, as the Petrified Forest locality is adjacent to least one graft 
accepted, and all four A.velox xenografts were rejected. both Interstate 40 and the Santa Fe railroad line, two accepted on 
Both intrapopulational allografts exchanged between routes that connect Petrified Forest with Albuquerque, 
the New Mexico lizards were accepted, but both of the New Mexico, where A. neomexicanus is common. all four lizards, 
intrapopulational allografts exchanged between the Because at least one interpopulational allograft was indicates that 
Petrified Forest lizards were rejected. accepted by each of the four A. neomexicanus, we sur-
Aside from gross examination of the lizards, we also mise that the two rejected interpopulational allografts lizards from the 
examined shed skins to determine graft acceptance. two popula-
Lizards shed frequently during the study, and often 
pieces of shed skin were large enough to encompass tions are his-
one or more grafts. We were able to salvage an excel- tocompatible, 
lent example from LACM 162344 from Petrified 
Forest, shed 4 or 5 April 1999.  Examination of this and therefore 
shed skin (Fig. 4) clearly shows both interpopulational likely geneti-
allografts, as well as the autograft, to be incorporated 
into the dermis to the degree that the shedding process cally identical 
did not distinguish between the different skins. (Cuellar 1977). 
This result 
eliminates the 
possibility that 
the Petrified 
Forest popu-
lation arose 
through a sepa-
rate hybridiza-
Fig. 3. Diagram and results of skin graft exchange in four A. tion between 
neomexicanus from Petrified Forest National Park, Arizona (A 
= LACM 162343, B = LACM 162344) and Bernalillo Co., New Fig. 4. (A) Photograph of preserved Aspidoscelis neomexicanus A. tigris and A. 
Mexico (C = LACM 162345, D = LACM 162346). Anterior of liz- (LACM 162344) from Petrified Forest National Park, Arizona 
ards are to top of diagram. On each lizard, from top to bottom, showing results of present skin grafting experiment. (B) inornatus. 
sequence of five grafts are autograft, intrapopulational allograft, Photograph of shed skin of same individual A. neomexicanus, 
interpopulational allograft (2), and xenograft donated by A. ve- shed 4 or 5 April 1999, showing acceptance (as indicated by 
lox (E = LACM 162350, F = LACM 162349). Open circles indicate coordinated shedding) of autograft (far left) and both inter-
graft acceptance, filled circles graft rejection. populational allografts.
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were not rejected due to histoincompatibility, but The Mystery of Adamana
rather to complications from surgery, such as infection. 
The other two rejected grafts that we predicted would When first discovered, in 1998, no previous speci-
have been accepted were exchanged between the two mens or reports of A. neomexicanus were known from 
individuals from Petrified Forest. However, because Arizona (Persons and Wright 1999a). However, shortly 
the two intrapopulational allografts between the two afterwards, while reviewing museum specimen records 
New Mexico lizards were both accepted, and because of whiptails from Arizona, we discovered a catalog 
the two Petrified Forest lizards each accepted inter- entry at the National Museum of Natural History 
populational allografts from the New Mexico lizards, (NMNH, Smithsonian Institution) of an A. tigris col-
it follows that the two Petrified Forest lizards would be lected on 5 June 1907 at Adamana, Apache County, 
histocompatable with each other. As with the rejected Arizona (USNM 58699). While A. tigris occurs else-  A unique 
interpopulational allografts, the rejected intrapopula- where in the Little Colorado River Basin, it is not 
tional allografts likely resulted not from an immune known from the immediate vicinity of Petrified Forest aspect of this 
response, but from infection or initial lack of adhesion (Drost et al. 2001). JWW and SWG examined the study is the use 
of grafts. specimen, which turned out to be an A. neomexicanus 
 A unique aspect of this study is the use of shed (Fig. 5). Persons and Wright (1999a) had already noted of shed skins 
skins in determination of graft acceptance. To our that the old Adamana station and siding of the Santa in determina-
knowledge, this has not been reported in other studies Fe railway was located only about 2 km (1.2 mi.) west 
of skin grafting in lizards. Coordinated shedding of of the area inhabited by A. neomexicanus at Petrified tion of graft 
graft and host skin strongly suggests that grafts have Forest (Fig. 6), and was therefore a possible source of acceptance. To 
been accepted and incorporated into the host skin, introduction (e.g., lizard stowaways in freight originat-
indicating histocompatibility between the two indi- ing near Albuquerque). Thus, it appeared that the spe- our knowledge, 
viduals. This technique could be useful in studies such cies may have been introduced to the Petrified Forest this has not 
as ours, in which graft acceptance disproves the null area sometime prior to 1907. Additional research and 
hypothesis that individuals are not genetically identi- field surveys, however, provided equivocal support for been reported 
cal. Although the eventual acceptance or rejection of this hypothesis. in other studies 
grafts in this study was apparent early on, we main- USNM 58699 was collected by Julius Hurter 
tained lizards alive for over six months for consistency (1842-1916) of St. Louis, Missouri, for whom Hurter’s of skin graft-
with other studies (e.g., Cuellar 1976, Cuellar 1977, Spadefoot (Scaphiopus hurterii) is named (Johnson ing in lizards. 
Cordes et al. 1990, Cuellar and Wright 1992). Ecdysis 2000). Hurter collected extensively in the Southwest, 
cycles in captive Aspidoscelis are frequently much short- and apparently spent the month of June 1907 primar- Coordinated 
er than the time required to confidently demonstrate ily in Albuquerque, Flagstaff, Phoenix, and Tucson. shedding of 
graft acceptance (personal observation). If coordinated Unfortunately, we could not locate additional data 
shedding does in fact indicate histocompatibility, then (such as field notes) at NMNH other than what was graft and host 
studies such as this could be terminated sooner, saving included in NMNH catalog entries; we did, however, skin strongly 
time and expense. find  a letter from the executor of Hurter’s estate in-
dicating that there was no field catalog, and that the suggests that 
grafts have 
been accepted 
and incorporat-
ed into the host 
skin, indicating 
histocompat-
ibility between 
the two indi-
viduals. 
Fig. 5. Aspidoscelis neomexicanus (USNM 58699) cataloged as being collected at Adamana, Apache Co., Arizona by Julius Hurter on 5 
June 1907. Photo by S.W. Gotte.
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If it were not 
for the current 
presence of A. 
Fig. 6. Location of old Adamana railway siding and Aspidoscelis neomexicanus (red dots) observed or collected south of the Puerco neomexicanus 
River at Petrified Forest National Park, Apache Co., Arizona, 1998-2000. at Petrified 
data on tags and jars was all that was known. Based given travel conditions in 1907 (e.g., passenger train Forest, it would 
on 85 amphibian and reptile specimens at NMNH rides of ~8-12 hours each between Albuquerque and 
collected by Hurter in June 1907, his itinerary for Flagstaff, and Flagstaff and Phoenix) it seems un- be logical to 
the month began in Albuquerque 1-3 June, followed likely that these dates are correct. In particular, it is surmise that, 
by a trip to Adamana or vicinity on 5 and 6 June, virtually impossible that Hurter collected lizards in 
a return to Albuquerque on 7 June, then a return Albuquerque, Adamana, and Phoenix on the same day. due to the 
to Arizona (Flagstaff, Phoenix, and Tucson) 10-30 If it were not for the current presence of A. neo- confusion 
June. Table 1 lists all specimens Hurter collected on 5 mexicanus at Petrified Forest, it would be logical to 
and 6 June, including the Adamana A. neomexicanus surmise that, due to the confusion regarding collection regarding col-
(USNM 58699). Anomalies in this two-day period dates, the “Adamana” specimen of A. neomexicanus was lection dates, 
include a specimen of A. tigris (USNM 58703) from likely actually collected in Albuquerque in the days 
Phoenix and a specimen of Phrynosoma hernandesi prior to 5 June. Hurter is listed as having collected 27 the “Adamana” 
(Greater Short-horned Lizard; USNM 58422) from specimens in Albuquerque on 1-3 June, including four specimen of A. 
Albuquerque, both supposedly collected the same specimens of A. neomexicanus (USNM 58433, 58435-
day (5 June) as the A. neomexicanus from Adamana. 7). However, it would be a strange coincidence indeed neomexicanus 
Two other Phoenix specimens collected in June have for such an error to involve a location almost exactly was likely actu-
suspect dates: USNM 58394 is a Urosaurus ornatus where the species was found 91 years later.
(Tree Lizard) collected 11 June, which is sandwiched Even before the discovery of the 1907 specimen of ally collected in 
between multiple specimens collected at Flagstaff 10 A. neomexicanus from Adamana we began surveying Albuquerque in 
and 12 June; and USNM 37962 is a Phrynosoma solare the area, hypothesizing that it could have been a point 
(Regal Horned Lizard) collected 16 June, the same day of introduction. On a total of eleven days in 1998, the days prior 
as other specimens collected at Flagstaff. Especially 1999, and 2000 we surveyed various locations on the to 5 June. 
Table 1. Amphibian and Reptile specimens at the National Museum of Natural History listed as being collected by Julius Hurter on 5 
and 6 June 1907.
USNM Species Locality Date (1907)
58403 Holbrookia maculata Adamana, Apache Co, AZ 5 June
58404 Holbrookia maculata Adamana, Apache Co., AZ 5 June
58422 Phrynosoma hernandesi Albuquerque, Bernalillo Co., NM 5 June
58610 Crotaphytus collaris Apache Co., AZ 5 June
58699 Aspidoscelis neomexicanus Adamana, Apache Co., AZ 5 June
58703 Aspidoscelis tigris Phoenix, Maricopa Co., AZ 5 June
38056 Crotaphytus collaris Near Adamana, Apache Co., AZ 6 June
57064 Ambystoma tigrinum Apache Co., AZ 6 June
57589 Anaxyrus woodhousii Apache Co., AZ 6 June
57590 Anaxyrus woodhousii Apache Co., AZ 6 June
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north side of the Puerco River (i.e., the Adamana side), unisexual species, which are similar in size (Stebbins 
including the railroad right-of-way, between 1.2 km 2003), probably affect each other to some (perhaps a 
(0.7 mi.) east of the Petrified Forest main park road large) degree. It seems likely that in most situations 
[which is 2.8 km (1.7 mi.) due east of Adamana], (e.g., particular habitat types or climatic regimes) one 
around the ruins of the Adamana siding, and up to or the other species would be ecologically superior. 
5.6 km (3.5 mi.) west of Adamana (Persons 2001, And, as appears to be the case with A. laredoensis in 
and unpublished data). The only whiptail we observed Texas, changing ecological conditions (perhaps in ways 
during these surveys was A. velox, which was common not immediately obvious to us) might be capable of 
throughout the area. We recorded a total of 162 A. dramatically altering relative abundances over short 
velox, including 25 during a single morning survey at periods of time. It therefore seems plausible that A. 
the Adamana site. During the same period, we con- neomexicanus first became established at Adamana in 
tinued to observe small numbers of A. neomexicanus at the late 1800s or early 1900s, expanded its population 
the original location of discovery south of the Puerco to include the area south of the Puerco River, and has 
River and west of the Petrified Forest main park road since disappeared from Adamana.
(Persons 2001; Fig. 6).
The Puerco River, which is essentially a large dry Summary
wash, should not be a barrier to A. neomexicanus. Discovery 
Thus, it was surprising to not find a single lizard north Results of a skin grafting study demonstrated that 
of the river. The absence of A. neomexicanus north of individuals of unisexual A. neomexicanus from the of a 1907 
the Puerco River, including around the ruins of the population discovered in 1998 at Petrified Forest specimen of A. 
Adamana railroad siding, would seem to suggest that National Park, Arizona are genetically identical to 
Adamana was not the point of introduction, but rather individuals of A. neomexicanus from within the native neomexicanus 
that the species was introduced on the south side of range of the species in the Rio Grande Valley in New from the his-
the river, in the area where it appears to be restricted Mexico. This result rules out the possibility that the 
to today. Furthermore, the limited distribution, espe- Petrified Forest population arose through an indepen- toric Adamana 
cially if it is indeed at the point of origin, might sug- dent hybridization between A. inornatus and A. tigris, railroad siding 
gest a recent introduction. However, it is difficult to and supports a hypothesis of human-mediated intro-
draw inferences of past distribution or abundance of duction. Discovery of a 1907 specimen of A. neomexi- near where A. 
unisexual whiptails based on present distribution and canus from the historic Adamana railroad siding near neomexicanus 
abundance. For example, populations of A. laredoensis where A. neomexicanus occurs today at Petrified Forest 
(Laredo Striped Whiptail), which is a diploid unisexual suggests the species may have been introduced over a occurs today at 
species that, like A. neomexicanus to its north, primar- century ago, perhaps as a stowaway on railroad cargo. Petrified For-
ily inhabits sandy, disturbed habitats along the lower Although inconsistencies in the collector’s itinerary 
Rio Grande in southern Texas, appear to fluctuate raise the possibility of cataloging errors and an alterna- est suggests 
dramatically. Aspidoscelis laredoensis consists of two tive explanation that the specimen was collected, on a the species 
distinct, independently derived clones (or species, de- different date, in Albuquerque, New Mexico, it seems 
pending on one’s taxonomic philosophy), designated unlikely that such an error would happen to involve a may have been 
LAR-A and LAR-B, which are broadly sympatric location where A. neomexicanus would be discovered introduced over 
with the much more widely distributed bisexual A. nearly a century later. While we may never know for 
gularis (Texas Spotted Whiptail or Common Spotted sure, a pre-1907 introduction of A. neomexicanus to a century ago, 
Whiptail) (Walker et al. 1987a, 1987b). In the 1980s, the Puerco River area at Petrified Forest seems the perhaps as a 
LAR-B was the dominant clone of A. laredoensis in the most likely. A second population of A. neomexicanus 
region where it co-occurred with LAR-A, but by the discovered at the south end of Petrified Forest in 2010, stowaway on 
1990s their relative abundances had reversed (Walker in an area where previous intensive surveys a decade railroad cargo.
et al. 1996, Paulissen et al. 2001). Also by the 1990s, earlier did not detect the species, may have originated 
A. gularis, which was formerly absent at many sites by inadvertent transport of one or more lizards from 
near the Rio Grande where A. laredoensis was abundant the Puerco River site, or, possibly, by an independent 
in the 1980s, had begun to make inroads (Walker et introduction from New Mexico.
al. 1996, Paulissen et al. 2001). Now, it appears that 
LAR-B, previously the more abundant form of A. Acknowledgements—We thank Charles Drost for 
laredoensis in many areas, may be absent; LAR-A is cheerfully tolerating hyperactive lizards, as well as an 
uncommon; and A. gularis is the dominant whiptail endless parade of escaped crickets, in his office during 
throughout the region (Persons 2020). Similarly, there the skin grafting study. Jeani Gaymer of the Northern 
is no reason to assume that, once established, a popu- Arizona University (NAU) Institutional Animal Care 
lation of A. neomexicanus at Adamana would remain and Use Committee (IACUC) assisted in numerous 
stable or expand at a predictable rate over the course ways. Andy Bridges provided information on lizard 
of a century. The ecology of co-occurring A. neomexi- monitoring and recent sightings of A. neomexicanus 
canus and A. velox has not been studied, but these two at Petrified Forest. Collections were made under per-
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mits to TBP from Petrified Forest National Park, the Rendu des Séances de la Société de Biogéographie 
Arizona Game and Fish Department, and the New 68:157-160.
Mexico Department of Game and Fish. This study is Degenhardt, W.G., C.W. Painter, and A.H. Price. 
NAU IACUC protocol no. 99-599. 1996. Amphibians and Reptiles of New Mexico. 
University of New Mexico Press, Albuquerque.
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F I C T I O N I was very 
Teen Herp Fantasies. Nobody should do this. excited as this 
Listening to you I get the music was a new 
Robert L. Bezy,  robertbezy@gmail.com locality for the 
species and my 
Dedicated to the memory of Charles Lowe and his three basic principles of herpetology.
All three are themes in these teen herp fantasies about perilous adventures done for love not money. photo voucher 
1. If it isn’t fun, don’t do it. would allow 
2. If it’s money you’re after, buster, go out and rob a goddam bank.
3. If you would not die for herpetology, you do not belong in it. me to publish 
1. Nactis the record and 
greased lightning across our lane just ahead,” yelled contribute 
Best Bud (BB) and I could hardly wait for the last day BB and I jammed on the breaks. Before Nellie with 
of classes. The bell of freedom rang and we could at her bald tires came to a stop BB was out the door to the 
long last herp non-stop. With our first drivers’ licenses and scooped the snake up from in front of a big rig conservation 
in hand, we gassed up old Nellie, a 1950 International barreling down the middle of the road. It was clearly 
Harvester Scout, and headed out on an adventure. a klauberi, Best Bud’s first, and he gave me a great hug of klauberi. My 
Spring was in full swing: the Foothill Paloverdes and we did the Nactis dance down the pavement in fascination with 
(Parkinsonia microphylla) were glorious and the Nactis front of the on-coming 18-wheeler.
(Chionactis, Shovel-nosed Snakes) would be issuing I was very excited as this was a new locality for conservation 
forth just after sundown. the species and my photo voucher would allow me to and publishing 
Puesta del sol, a chug of cold coffee saturated with publish the record and contribute to the conservation 
sugar, and we were cruising by the start of the Nactis of klauberi. My fascination with conservation and was growing.
golden hour. “Hot dog! There’s one streaking like publishing was growing.
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