The genus Sceloporus is a diverse clade of lizards that exhibits substantial variation in chromosome numbers and sex chromosome heteromorphisms, 2 features of the genome that are static among most other pleurodont iguanian lizards. Evolutionary changes to the fundamental number of chromosomes are hypothesized to be a primary factor responsible for driving the diversification of Sceloporus. We explore the patterns of chromosome evolution in Sceloporus using a combination of ancestral state estimations and species diversification tests. Phylogenetic relationships and divergence times within Sceloporus (53 species representing all 19 species groups) are estimated using 4 nuclear genes (>3.3 kb) and relaxed-clock analyses that incorporate a fossil calibration on the root of the tree. We test the hypothesis that chromosome evolution is correlated with shifts in species diversification using cross-validation predictive densities, a new Bayesian approach for modeling the number of species that are predicted to have evolved in the absence of a certain historical event (e.g., a change in chromosome numbers). Results of the cross-validation predictive densities approach indicate that chromosomal evolution is correlated with significantly higher species diversity than predicted under the background rate of diversification in Sceloporus. We conclude by discussing the future of comparative cytogenetic investigations in Sceloporus.

Keywords:
Bayesian analysis, Character evolution, Genome, Phrynosomatidae, Speciation
1.
Arévalo E, Porter CA, Gonzalez A, Mendoza F, Camarillo JL, Sites JW Jr: Population cytogenetics and evolution of the Sceloporus grammicus complex (Iguanidae) in central Mexico. Herpetol Monogr 5:79–115 (1991).
2.
Arévalo E, Davis SK, Casas G, Lara G, Sites JW Jr: Parapatric hybridization between chromosome races of the Sceloporus grammicus complex: structure of the Ajusco transect. Copeia 1993:252–272 (1993).
3.
Arévalo E, Davis SK, Sites JW Jr: Mitochondrial DNA sequence divergence and phylogenetic relationships among eight chromosome races of the Sceloporus grammicus complex (Phrynosomatidae) in central Mexico. Syst Biol 43:387–418 (1994).
4.
Barton NH, Hewitt GM: Hybrid zones and speciation, in Atchley WR, Woodruff DS (eds): Evolution and Speciation: Essays in Honor of M.J.D. White, pp 109–145 (Cambridge University Press, Cambridge 1981).
5.
Bickham JW: Patterns and modes of chromosomal evolution in reptiles, in Sharma AK, Sharma A (eds): Chromosomes in Evolution of Eukaryotic Groups, Vol. II, pp 13–40 (CRC Press, Boca Raton 1984).
6.
Cole CJ: Karyotypes and evolution of the spinosus group of lizards in the genus Sceloporus. Am Mus Novit 2431:1–47 (1970).
7.
Cole CJ: Karyotypes of the five monotypic species groups of lizards in the genus Sceloporus. Am Mus Novit 2450:1–17 (1971a).
8.
Cole CJ: Karyotypes and relationships of the pyrocephalus group of lizards in the genus Sceloporus. Herpetologica 27:1–8 (1971b).
9.
Cole CJ: Chromosomal variation in North American fence lizards (genus Sceloporus; undulatus species group). Syst Zool 21:357–363 (1972).
10.
Cole CJ: Karyotype and systematic status of the sand dune lizard (Sceloporusgraciosus arenicolous) of the American Southwest. Herpetologica 31:288–293 (1975).
11.
Cole CJ: Chromosomal aberration and chromatid exchange in the North American fence lizard, Sceloporus undulatus (Reptilia, Iguanidae). Copeia 1977:53–59 (1977).
12.
Cole CJ, Lowe CH: Sex chromosomes in lizards. Science 155:1028–1029 (1967).
13.
Cole CJ, Lowe CH: The karyotype of a lizard (Sceloporus virgatus) and description of a spontaneous chromosomal aberration. Arizona Acad Sci 5:128–130 (1968).
14.
Cox RM, Skelly SL, John-Alder HB: A comparative test of adaptive hypotheses for sexual size dimorphism in lizards. Evolution 57:1653–1669 (2003).
15.
Dobzhansky T: Genetics and the Origin of Species (Columbia University Press, New York 1951).
16.
Dobzhansky T: Genetics of the Evolutionary Process (Columbia University Press, New York 1970).
17.
Drummond AJ, Rambaut A: BEAST: Bayesian evolutionary analysis by sampling trees. BMC Evol Biol 7:214–221 (2007).
18.
Flores-Villela O, Kjer KM, Benabib M, Sites JW Jr: Multiple data sets, congruence, and hypothesis testing for the phylogeny of basal groups of the lizard genus Sceloporus (Squamata, Phrynosomatidae). Syst Biol 49:713–739 (2000).
19.
Gorman GC, Atkins L, Holzinger T: New karyotypic data on 15 genera of lizards in the family Iguanidae, with a discussion of taxonomic and cytological implications. Cytogenetics 6:286–299 (1967).
20.
Graves JAM: Weird animal genomes and the evolution of vertebrate sex and sex chromosomes. Ann Rev Genet 42:565–586 (2008).
21.
Hall WP: Preliminary chromosome studies of some Nevada test site lizards. 45th Annual Meeting of the American Society of Ichthyologists and Herpetologists, Lawrence, KS (1965).
22.
Hall WP: Comparative Population Cytogenetics, Speciation, and Evolution of the Iguanid Lizard Genus Sceloporus. PhD dissertation, Harvard University, Cambridge, MA (1973).
23.
Hall WP: Chromosomes, speciation, and evolution of Mexican iguanid lizards. Natl Geogr Soc Res Repts 12:309–329 (1980).
24.
Hall WP: Modes of speciation and evolution in the sceloporine iguanid lizards I. Epistemology of the comparative approach and introduction to the problem, in Rhodin AGJ, Miyata K (eds): Advances in Herpetology and Evolutionary Biology, pp 643–679 (Museum of Comp Zool, Harvard University, Cambridge, MA 1983).
25.
Hall WP: Chromosome variation, genomics, speciation and evolution in Sceloporus lizards. Cytogenet Genome Res, this issue(2009).
26.
Hall WP, Selander RK: Hybridization of karyotypically differentiated populations in the Sceloporus grammicus complex (Iguanidae). Evolution 27:226–242 (1973).
27.
Harmon LJ, Schulte JA 2nd, Larson A, Losos JB: Tempo and mode of evolutionary radiation in iguanian lizards. Science 310:961–964 (2003).
28.
Harrison RG: Hybrid zones: windows on the evolutionary process. Oxford Surv Evol Biol 7:69–128 (1990).
29.
Holman JA: A Pleistocene herpetofauna from Eddy County, New Mexico. Tex J Sci 22:29–39 (1970).
30.
Holman JA: Pleistocene Amphibians and Reptiles of North America (Oxford University Press, New York 1995).
31.
Jackson L, Hunsaker D: Chromosome morphology of sceloporine lizards (Sceloporus occidentalis and S graciosus). Experientia 26:198–199 (1970).
32.
Jaenike J: Sex chromosome meiotic drive. Annu Rev Ecol Syst 32:25–49 (2001).
33.
Key KHL: The concept of stasipatric speciation. Syst Zool 17:14–22 (1968).
34.
King M: Species Evolution: The Role of Chromosome Change (Cambridge University Press, New York 1993).
35.
Larsen KR, Tanner WW: Numeric analysis of the lizard genus Sceloporus with special reference to cranial osteology. Great Basin Nat 34:1–41 (1974).
36.
Larsen KR, Tanner WW: Evolution of the sceloporine lizards (Iguanidae). Great Basin Nat 35:1–20 (1975).
37.
Leaché AD: Species tree discordance traces to phylogeographic clade boundaries in North American fence lizards (Sceloporus). Syst Biol 58:547–559 (2009).
38.
Leaché AD: Species trees for spiny lizards (genus Sceloporus): identifying points of concordance and conflict between nuclear and mitochondrial data. Mol Phylogenet Evol 54:162–171 (2010).
39.
Leaché AD, Cole CJ: Hybridization between multiple fence lizard lineages in an ecotone: locally discordant variation in mitochondrial DNA, chromosomes, and morphology. Mol Ecol 16:1035–1054 (2007).
40.
Leaché AD, Mulcahy DG: Phylogeny, divergence times, and species limits of spiny lizards (Sceloporus magister species group) in western North American deserts and Baja California. Mol Ecol 16:5216–5233 (2007).
41.
Lewis PO: A likelihood approach to estimating phylogeny from discrete morphological character data. Syst Biol 50:913–925 (2001).
42.
Lowe CH, Cole CJ, Patton JL: Karyotype evolution and speciation in lizards (genus Sceloporus) during the evolution of the North American desert. Syst Zool 16:296–300 (1967).
43.
Maddison WP, Maddison DR: MESQUITE: a modular system for evolutionary analysis, v2.5. Available from http://mesquiteproject.org (2009).
44.
Mank JE: Sex chromosomes and the evolution of sexual dimorphism: lessons from the genome. Am Nat 173:141–150 (2009).
45.
Marshall JC, Sites JW Jr: A comparison of nuclear and mitochondrial cline shapes in a hybrid zone in the Sceloporus grammicus complex (Squamata; Phrynosomatidae). Mol Ecol 10:435–449 (2001).
46.
Marshall JC, Arévalo E, Benavides E, Sites JL, Sites JW Jr: Delimiting species: comparing methods for Mendelian characters using lizards of the Sceloporus grammicus (Squamata: Phrynosomatidae) complex. Evolution 60:1050–1065 (2006).
47.
Mindell DP, Sites JW Jr, Graur D: Speciational evolution: a phylogenetic test with allozymes in Sceloporus (Reptilia). Cladistics 5:49–61 (1989).
48.
Moore BR, Donoghue MJ: A Bayesian approach for evaluating the impact of historical events on rates of diversification. Proc Natl Acad Sci USA 106:4307–4312 (2009).
49.
Noor MAF, Grams KL, Bertucci LA, Reiland J: Chromosomal inversions and the reproductive isolation of species. Proc Natl Acad Sci USA 98:12084–12088 (2001).
50.
Pagel M: The maximum likelihood approach to reconstructing ancestral character states of discrete characters on phylogenies. Syst Biol 48:612–622 (1999).
51.
Pagel M, Meade A: Bayesian analysis of correlated evolution of discrete characters by reversible-jump Markov chain Monte Carlo. Am Nat 167:808–825 (2006).
52.
Pagel M, Meade A: BayesTraits, v1.0. Available from http://www.evolution.rdg.ac.uk/ (2009).
53.
Pagel M, Meade A, Barker D: Bayesian estimation of ancestral character states on phylogenies. Syst Biol 53:673–684 (2004).
54.
Panithanarak T, Hauffe HC, Dallas JF, Glover A, Ward RG, Searle JB: Linkage-dependent gene flow in a house mouse chromosomal hybrid zone. Evolution 58:184–192 (2004).
55.
Paull D, Williams EE, Hall WP: Lizard karyotypes from the Galapagos Islands: chromosomes in phylogeny and evolution. Breviora 441:1–31 (1976).
56.
Pennock LA, Tinkle DW, Shaw MW: Minute Y chromosome in the lizard genus Uta (family Iguanidae). Cytogenetics 8:9–19 (1969).
57.
Porter CA, Sites JW Jr: Normal disjunction in Robertsonian heterozygotes from a highly polymorphic lizard population. Cytogenet Cell Genet 39:250–257 (1985).
58.
Porter CA, Sites JW Jr: Evolution of Sceloporus grammicus complex (Sauria: Iguanidae) in central Mexico: population cytogenetics. Syst Zool 35:334–358 (1986).
59.
Porter CA, Sites JW Jr: Evolution of Sceloporus grammicus complex in central Mexico II. Studies on rates of nondisjunction and the occurrence of spontaneous chromosomal mutations. Genetica 75:131–144 (1987).
60.
Porter CA, Hamilton MJ, Sites JW Jr, Baker RJ: Location of ribosomal DNA in chromosomes of squamate reptiles: systematic and evolutionary implications. Herpetologica 47:271–280 (1991).
61.
Rambaut A, Drummond AJ: TRACER, v1.4.1. Available from http://tree.bio.ed.ac.uk/software/tracer/ (University of Oxford, Oxford 2009).
62.
Reed KM, Sites JW Jr: Female fecundity in a hybrid zone between chromosome races of the Sceloporus grammicus complex (Sauria, Phrynosomatidae). Evolution 49:61–69 (1995).
63.
Reed KM, Sudman PD, Sites JW Jr, Greenbaum IF: Synaptonemal complex analysis of sex chromosomes in two species of Sceloporus. Copeia 1990:1122–1129 (1990).
64.
Reed KM, Sites JW Jr, Greenbaum IF: Chromosomal synapsis and the meiotic process in male mesquite lizards, Sceloporus grammicus complex. Genome 35:398–408 (1992a).
65.
Reed KM, Sites JW Jr, Greenbaum IF: Synapsis, recombination, and meiotic segregation in the mesquite lizard, Sceloporus grammicus complex I. Pericentric inversion heteromorphism of the F5 cytotype. Cytogenet Cell Genet 61:40–45 (1992b).
66.
Reed KM, Sites JW Jr, Greenbaum IF: Synapsis, recombination, and meiotic segregation in the mesquite lizard, Sceloporus grammicus complex II. Fission heteromorphism of the FM2 cytotype and evolution of chromosome 2. Cytogenet Cell Genet 61:46–54 (1992c).
67.
Reed KM, Greenbaum IF, Sites JW Jr: Cytogenetic analysis of chromosomal intermediates from a hybrid zone between two chromosome races of the Sceloporus grammicus complex (Sauria, Phrynosomatidae). Evolution 49:37–47 (1995a).
68.
Reed KM, Greenbaum IF, Sites JW Jr: Dynamics of a novel chromosomal polymorphism within a hybrid zone between two chromosome races of the Sceloporus grammicus complex (Sauria, Phrynosomatidae). Evolution 49:48–60 (1995b).
69.
Rieseberg LH: Chromosomal rearrangements and speciation. Trends Ecol Evol 16:351–358 (2001).
70.
Rieseberg LH, Whitton J, Gardner K: Hybrid zones and the genetic architecture of a barrier to gene flow between two sunflower species. Genetics 152:713–727 (1999).
71.
Robinson MD, Van Devender TR: Miocene lizards from Wyoming and Nebraska. Copeia 1973:698–704 (1973).
72.
Rogers AR, Harpending H: Population growth makes waves in the distribution of pairwise genetic differences. Mol Biol Evol 9:552–569 (1992).
73.
Sites JW Jr: Chromosome evolution in the iguanid lizard Sceloporus grammicus. 1. Chromosome polymorphisms. Evolution 37:38–53 (1983).
74.
Sites JW Jr: Chromosomal variation in the Sceloporus grammicus complex (Sauria, Phrynosomatidae), in Sumner AT, Chandley AC (eds): Chromosomes Today, Vol 11, pp 137–147 (Chapman & Hall, London 1993).
75.
Sites JW Jr: Review: Chromosomal evolution (‘Species Evolution: The Role of Chromosome Change.’ M. King). Evolution 49:218–222 (1995).
76.
Sites JW Jr, Davis SK: Phylogenetic relationships and molecular variability within and among six chromosome races of Sceloporus grammicus (Sauria, Iguanidae) based on nuclear and mitochondrial markers. Evolution 43:296–317 (1989).
77.
Sites JW Jr, Moritz C: Chromosomal evolution and speciation revisited. Syst Zool36:153–174 (1987).
78.
Sites JW Jr, Reed KM: Chromosome evolution, speciation, and systematics: some relevant issues. Herpetologica 50:237–249 (1994).
79.
Sites JW Jr, Porter CA, Thompson P: Genetic structure and chromosomal evolution in the Sceloporus grammicus complex. Natl Geogr Res 3:343–362 (1987).
80.
Sites JW Jr, Archie JW, Cole CJ, Villela OF: A review of phylogenetic hypotheses for lizards of the genus Sceloporus (Phrynosomatidae): implications for ecological and evolutionary studies. B Am Mus Nat Hist 213:1–110 (1992).
81.
Sites JW Jr, Davis SK, Hutchison DW, Maurer BA, Lara G: Parapatric hybridization between chromosome races of the Sceloporus grammicus complex (Phrynosomatidae): structure of the Tulancingo Transet. Copeia 1993:373–398 (1993).
82.
Sites JW Jr, Barton NH, Reed KM: The genetic structure of a hybrid zone between two chromosome races of the Sceloporus grammicus complex (Sauria, Phrynosomatidae) in central Mexico. Evolution 49:9–36 (1995).
83.
Smith HM: The Mexican and Central American lizards of the genus Sceloporus. Zool Ser Field Mus Nat Hist 26:1–397 (1939).
84.
Smith HM, Taylor EH: An annotated checklist and key to the reptiles of Mexico exclusive of the snakes. Bull US Natl Mus 199:1–253 (1950).
85.
Walsh JB: Rate of accumulation of reproductive isolation by chromosome rearrangements. Am Nat 120:510–532 (1982).
86.
Waters PD, Marshall Graves JA, Thompson K, Sankovic N, Ezaz T: Identification of cryptic sex chromosomes and isolation of X- and Y-borne genes, in Murphy WJ (ed): Methods in Molecular Biology: Phylogenomics, pp 239–251 (Humana Press Inc., Totowa 2009).
87.
White MJD: Models of speciation. Science 159:1065–1070 (1968).
88.
White MJD: Animal Cytology and Evolution (Cambridge University Press, London 1973).
89.
White MJD: Modes of Speciation (WH Freeman, San Francisco 1978a).
90.
White MJD: Chain processes in chromosomal speciation. Syst Zool 27:285–298 (1978b).
91.
Wiens JJ: Phylogenetic evidence for multiple losses of a sexually selected character in phrynosomatid lizards. Proc R Soc Lond B 266:1529–1535 (1999).
92.
Wiens JJ, Reeder TW: Phylogeny of the spiny lizards (Sceloporus) based on molecular and morphological evidence. Herp Monographs 11:1–101 (1997).
93.
Wiens JJ, Kuczynski CA, Arif S, Reeder TW: Phylogenetic relationships of phrynosomatid lizards based on nuclear and mitochondrial data, and a revised phylogeny for Sceloporus. Mol Phylogenet Evol 54:150–161 (2010).
94.
Yatkola DA: Mid-Miocene lizards from Western Nebraska. Copeia 1976:645–654 (1976).
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