Anolis (Norops) nebulosus Wiegmann

Castiglia, Riccardo, Annesi, Flavia, Bezerra, Alexandra M. R., García, Andrés & Flores-Villela, Oscar, 2010, Cytotaxonomy and DNA taxonomy of lizards (Squamata, Sauria) from a tropical dry forest in the Chamela-Cuixmala Biosphere Reserve on the coast of Jalisco, Mexico, Zootaxa 2508, pp. 1-29 : 17-18

Anolis (Norops) nebulosus Wiegmann (Clouded anole)

Specimens analysed: two males (CEAC20, CEAC21)

Distribution: Mexican endemic. Occurring from southern Sonora and northern Sinaloa, to western Guerrero, entering the Balsas Basin up to the southern State of Mexico.

Subspecies: not recognized.

The karyotype of A. nebulosus was briefly described by Gorman (1973) from an individual male that shows 2n = 30, with 13 macro- and 17 microchromosomes, and this karyotype has been reported as a possible case of X-Y heteromophism. However, Gorman (1973) did not show the karyotype. Lieb (1981) in his unpublished dissertation reported two different karyotypes for this species. Males from Sonora showed a karyotype with 2n = 36 chromosomes, 20 macro-chromosomes and 8 pairs of micro-chromosomes, including a pair of heteromorphic chromosomes. Males from Nayarit, Colima, Jalisco and Michoacán showed 2n = 30 chromosomes, of which 14 were macro-chromosomes, and the rest micro-chromosomes. A single pair of heterochromosomes was interpreted as XY sex chromosomes. Here we show for the first time the male karyotype of this species ( Fig. 9 ). Diploid number is 2n = 30 with 14 macro- and 16 microchromosomes.

All the macrochromosomes are biarmed, metacentric or submetacentric, as well as the first two pairs of microchromosomes. Among the macrochromosomes, three pairs of heteromorphic chromosomes have been identified (tentatively pair numbers 5, 6 and 7, Fig. 9 ). These chromosomes differ in size and centromere position.

The karyotype described here is probably identical to the one described by Lieb (1981). However, we identified six unpaired chromosomes (rather than one). This is congruent with the complex system involving multiple sex chromosomes already described in other species of the genus (data from the ‘‘chromorep’’ database: http://www.scienze.univpm.it/professori/chromorep.pdf). Additional data on male and female individuals from this species are required to understand the significance of this bizarre karyotype.

DNA taxonomy: neither gene sequence for this species is present in GenBank. We used the NDH2 gene and flanking tRNAs (596 bp) to assess its phylogenetic affinity. This sequence was aligned with all the other species of Norops present in GenBank (about 160 species). For ML the selected model was the Hasegawa, Kishino, Yano (HKY) model ( Hasegawa et al. 1985) with a proportion of invariable sites I = 0.2664, rate variation among sites (+G), and a gamma distribution shape parameter of 0.7310.

The phylogenetic position of the species was not well supported probably due to the short sequence analysed (not shown). A relationship between N. nebulosus with N. quercorum and N. nebuloides , two other Mexican endemics, was supported with low bootstrap (50%) only by ML tree. These are the first data reporting the relationships of N. nebulosus with N. quercorum and N. nebuloides . In fact only N. quercorum was included in the same morphological species group with N. nebulosus while N. nebuloides belongs to a different group recognized on the basis of morphological characters ( Etheridge 1960; Lieb 1981; Nicholson 2002).

Figures

FIGURE 9. Karyotype of Norops nebulosus, male (2 n = 30). Note the three pairs of heteromorphic chromosomes (pairs 5, 6 and 7).