A Taxonomic Revision of the Phrynosoma Douglasii Species Complex (Squamata: Phrynosomatidae)
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Zootaxa 4015 (1): 001–177 ISSN 1175-5326 (print edition) www.mapress.com/zootaxa/ Monograph ZOOTAXA Copyright © 2015 Magnolia Press ISSN 1175-5334 (online edition) http://dx.doi.org/10.11646/zootaxa.4015.1.1 http://zoobank.org/urn:lsid:zoobank.org:pub:6C577904-2BCC-4F84-80FB-E0F0EEDF654B ZOOTAXA 4015 A taxonomic revision of the Phrynosoma douglasii species complex (Squamata: Phrynosomatidae) RICHARD R. MONTANUCCI1 1Department of Biological Sciences, Clemson University, Clemson, SC 29634-0314. E-mail: [email protected] Magnolia Press Auckland, New Zealand Accepted by A. Bauer: 16 Jun. 2015; published: 11 Sept. 2015 RICHARD R. MONTANUCCI A taxonomic revision of the Phrynosoma douglasii species complex (Squamata: Phrynosomatidae) ( Zootaxa 4015) 177 pp.; 30 cm. 11 Sept. 2015 ISBN 978-1-77557-789-8 (paperback) ISBN 978-1-77557-790-4 (Online edition) FIRST PUBLISHED IN 2015 BY Magnolia Press P.O. 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ISSN 1175-5326 (Print edition) ISSN 1175-5334 (Online edition) 2 · Zootaxa 4015 (1) © 2015 Magnolia Press MONTANUCCI Table of contents Abstract . 3 Introduction . 3 Materials and methods . 5 Results and discussion . 10 Taxonomic accounts . 25 Phrynosoma brevirostris Girard 1858a . 25 Phrynosoma bauri sp. nov. 33 Phrynosoma diminutum sp. nov. 39 Phrynosoma douglasii (Bell 1828) . 45 Phrynosoma hernandesi hernandesi Girard 1858a . 51 Phrynosoma hernandesi ornatum Girard 1858b, comb. nov. 61 Phrynosoma ornatissimum ornatissimum Girard 1858a . 67 Phrynosoma ornatissimum brachycercum Smith 1942, comb. nov. 75 Hybridization between Phrynosoma hernandesi and Phrynosoma ornatissimum . 82 Summary . 110 Acknowledgements . 111 References . 112 Appendix I . 117 Appendix II . 163 Abstract Short-horned lizards (Phrynosoma douglasii species complex) occur throughout the inter-montane West and Great Plains of western North America. The comparative morphology and color pattern variation of short-horned lizards was studied in 3,174 specimens. Multivariate analyses of 20 morphological and color-pattern characters were applied to 977 speci- mens, and univariate statistics were summarized for 52 samples totaling 1,134 specimens. The results of the morpholog- ical data analyses support the recognition of P. douglasii (Bell 1828) as a distinct species, and the resurrection of P. brevirostris Girard 1858a and P. ornatissimum Girard 1858a as species distinct from P. hernandesi Girard 1858a. Two new species allied to P. brevirostris are described: P. bauri sp. nov. from the eastern plains of Colorado and northeastern New Mexico, southeastern Wyoming and southwestern Nebraska south of the North Platte River, and P. diminutum sp. nov. endemic to the San Luis Valley of southern Colorado and northern New Mexico. The Mexican taxon brachycercum Smith 1942 is reassigned as a subspecies of P. ornatissimum, based on non-discrete character differences and overall morpho- metric similarity. The ranges of P. hernandesi and P. ornatissimum broadly overlap in central New Mexico, the former taxon occupying the coniferous forests of disjunct mountain ranges, the latter occuring in the surrounding desert grass- lands. Principal components analysis has revealed morphological evidence of hybridization where the two taxa meet, gen- erally within ecotones between montane forest associations and grasslands. Principal components analysis has also revealed a high level of morphological variability in populations occurring in the Colorado Plateau region of northeastern Arizona, northwestern New Mexico, extreme southwestern Colorado and adjacent Utah. The evidence suggests that these populations arose through past hybridization between the two species. The taxon ornatum Girard 1858b, although sharing several traits with P. brevirostris, is morphologically close to P. hernandesi. It is regarded as a stabilized population of hybrid origin, but treated taxonomically as a subspecies of P. hernandesi. The taxonomic arrangement in this study, with the exception of P. douglasii, is largely discordant with the proposed taxonomy from a previously published study based on mitochondrial DNA sequence data. Key words: geographic variation, morphology, Phrynosoma, Phrynosomatidae, species delimitation, systematics, taxonomy Introduction As presently conceptualized, the Phrynosoma douglasii species complex consists of two species, Phrynosoma douglasii (Bell) and Phrynosoma hernandesi Girard, following Zamudio et al. (1997). The former species occurs along the Cascade Range in the Pacific Northwest region and the deserts as far east as southern Idaho (Stebbins, 1985; Nussbaum et al. 1983). The latter is widely distributed from the mixed grass prairies of southern Alberta and southwestern Saskatchewan (Powell & Russell, 1998) southward through the woodlands and grasslands of the Great Basin, Rocky Mountains, western Great Plains and eastern slopes of the Sierra Madre Occidental, reaching central Zacatecas, Mexico (Stebbins, 1985; Smith & Flores-Villela, 1994). TAXONOMY OF PHRYNOSOMA DOUGLASII Zootaxa 4015 (1) © 2015 Magnolia Press · 3 Phrynosoma douglasii was originally described as Agama douglassii [sic] by Thomas Bell (1828) on the basis of two specimens in the British Museum of Natural History collected by the British botanist and explorer, David Douglas. The species was transferred to the genus Phrynosoma by J. Wagler (1830) whose action was followed by J. E. Gray (1831). In 1858, Charles Girard (1858a, b) described several new species of short-horned lizards under the subgenus Tapaya: T. brevirostris, T. hernandesi, and T. ornatissima. In addition, the name Phrynosoma ornatum appeared as a caption in plate 21 of Girard’s (1858b) atlas that accompanied his text (Girard, 1858a); however, in the text it was treated as a synonym of Tapaya douglassii [sic]. As explained by Stejneger (1919), Girard was uncertain as to the validity of Phrynosoma ornatum and while his text was in press, he decided to place the name in the synonymy of T. douglasii. However, Girard’s decision came too late to alter the caption for the illustrations in his atlas. Stejneger (1919) regarded the name and associated illustrations as a valid description. In considering the status of ornatum, it was Stejneger’s opinion that this taxon was not related to P. hernandesi, but was sufficiently distinct from P. douglasii to be treated as a subspecies. Therefore, he revived the name and applied it to the populations inhabiting the Salt Lake Valley of Utah. Smith (1946) and Reeve (1952) followed Stejneger’s suggested treatment. Prior to Reeve’s (1952) monograph on the genus, all of Girard’s species were relegated to subspecies of Phrynosoma douglasii as follows: P. d. ornatissimum by H. C. Yarrow (1875); P. d. hernandesi by E. D. Cope (1900); P. d. ornatum by Stejneger (1919), and P. d. brevirostre by H. M. Smith (1946). Reeve (1952) continued with the accepted taxonomy at that time, and did not elevate any of Girard’s taxa to full species. Smith (1946:58) recognized that unresolved questions surrounded the status and validity of Girard’s species, and commented (p. 301) …“the douglassii [sic] ‘complex’ of the horned lizards is seriously in need of careful study; probably this is the outstanding problem remaining to be studied in the systematics of the United States lizards.” The taxonomic difficulties presented by this group of lizards have their origin in the species descriptions published by Girard (1858a). Girard did not prepare separate descriptions and diagnoses, although the information in each account under the heading “SPEC. CHAR.” could be assumed to constitute a diagnosis. More problematic, Girard did not designate type specimens in his species accounts. Type designations can be found as penciled annotations in the ledger entries at the Smithsonian Institution (USNM), but it is not known when, or by whom, these designations were made. It is suspected that Leonhard Stejneger may have made some of the type designations decades later (S. Gotte, personal communication). In some cases, discrepancies between Girard’s original descriptions and the designated type material have been found. Adding to these difficulties, Girard’s descriptive accounts are brief, and in most cases, incomplete. Consequently, confusion and disagreement concerning the validity and appropriate rank of the proposed short-horned lizard taxa emerged at the very beginning and have persisted to the present. A seemingly intractable problem has been the question of the status of P. d. ornatissimum as a species distinct from P. d. hernandesi. Stejneger (1890) regarded the two taxa as separate species and provided detailed descriptions of their differences. But contrary to Girard’s original statement that P. ornatissimum inhabits the mountainous region of New Mexico, Stejneger reported that P. hernandesi occurs in the forested parts of Arizona, Colorado, Utah, and New Mexico, whereas P. ornatissimum occupies the deserts of those regions. Cope (1900) treated the two taxa as subspecies of P. douglassii [sic], but he apparently lacked any clear