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Pattern of chromosomal changes in ‘beta’ Anolis (Norops group) (Squamata: Polychrotidae) depicted by an ancestral state analysis

Riccardo Castiglia1*, Oscar Flores-Villela2, Alexandra Maria Ramos Bezerra34, Antonio Muñoz5 and Ekaterina Gornung1

Author Affiliations

1 Dipartimento di Biologia e Biotecnologie ‘Charles Darwin’, Università di Roma ‘La Sapienza’, via A. Borelli 50, Rome 00161, Italy

2 Museo de Zoología, Facultad de Ciencias, Universidad Nacional Autónoma de México, A.P. 70-399, Coyoacán, Mexico, DF 04510, Mexico

3 Departamento de Zoologia, Universidade de Brasília, IB, Brasilia, DF 70910-900, Brazil

4 Current address: Laboratório de Biologia e Parasitologia de Mamíferos Silvestres Reservatórios, IOC-FIOCRUZ, Rio de Janeiro CEP 21045-900, Brazil

5 El Colegio de la Frontera Sur - San Cristóbal de las Casas Carr. Panamericana y Av. Periférico Sur s/n 29290, San Cristóbal de las Casas, Chiapas, Mexico

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Zoological Studies 2013, 52:60  doi:10.1186/1810-522X-52-60

Published: 13 December 2013

Abstract

Background

Neotropical lizards, genus Anolis (Polychrotidae), with nearly 380 species, are members of one of the most diversified genera among amniotes. Herein, we present an overview of chromosomal evolution in ‘beta’ Anolis (Norops group) as a baseline for future studies of the karyotypic evolution of anoles. We evaluated all available information concerning karyotypes of Norops, including original data on a recently described species, Anolis unilobatus. We used the phylogeny of Norops based on DNA sequence data to infer the main pattern of chromosomal evolution by means of an ancestral state analysis (ASR).

Results

We identified 11 different karyotypes, of which 9 in the species had so far been used in molecular studies. The ASR indicated that a change in the number of microchromosomes was the first evolutionary step, followed by an increase in chromosome numbers, likely due to centric fissions of macrochromosomes. The ASR also showed that in nine species, heteromorphic sex chromosomes most probably originated from six independent events.

Conclusions

We observed an overall good correspondence of some characteristics of karyotypes and species relationships. Moreover, the clade seems prone to sex chromosome diversification, and the origins of five of these heteromorphic sex chromosome variants seem to be recent as they appear at the tip nodes in the ancestral character reconstruction. Karyotypic diversification in Norops provides an opportunity to test the chromosomal speciation models and is expected to be useful in studying relationships among anole species and in identifying cryptic taxa.

Keywords:
Anole; Anolis; Chromosomal evolution; Cytogenetics; Norops; Sex chromosomes; Systematics