Complex chromosomal variation in natural populations of the Jamaican lizard Anolis grahami

Abstract

Studies of chromosomal variation were undertaken in Anolis grahamk Multiple fission events and extensive variation involving heterochromatic sequences were observed. Distribution of the chromosomal variants did not coincide with subspecies borders. Chromosome numbers ranging from 30 to 37 were observed in both morphological subspecies; different rearrangements were involved in each. C-banding studies revealed cryptic variation in a large macrochromosome of some populations of A. g. grahamL and the presence of an additional heterochromatic arm in A. g. aquarum. Patterns of distribution of various forms, including widespread polymorphism, suggest significant dispersal of Anolis grahami, and little selection against chromosomal heterozygotes.

Rate of Chromosome changes and Speciation in Reptiles

“…In fact, groups characterised by karyotypes which for their wide diffusion and stability are considered as frozen formulae (Bickham, 1984;Olmo, 1986), like the one with 12 biarmed macrochromosomes and 24 microchromosomes, common among iguanids and agamids (Gorman, 1973;Olmo 1986), or the one with 36 uniarmed macrochromosomes and two microchromosomes of lacertids (Olmo et al, 1990), also include numerous taxa endowed with high chromosome variability, like Sceloporus (Hall & Selander, 1973;Sites, 1983), Anolis (Blake, 1986), Liolaemus (Lamborot, Espinoza & Alvarez, 1979;Lamborot & Alvarez-Sarret, 1993) and some species of Lacerta (Odierna et al, 1996;in den Bosch et al, 2003). It is also interesting to note that in these taxa the high karyotypic variability is not always related to phases of adaptive radiation, but is also found in species made up of small, geographically isolated demes (Hall & Selander, 1973;Sites, 1983;Odierna et al, 1996).…”

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

“…2n = 30~37. Anolis grahami was characterized by extensive chromosomal polymorphism with chromosome numbers (2n) ranging 30~37 due to multiple fission events within the macrochromosomal complement as well as by eight or nine pairs of microchromosomes (Blake 1986). Only the karyotype with 2n = 32 is shown as an ideogram in Figure 2.…”

“…In fact, the presently studied A. unilobatus had several submetacentric chromosomes probably obtained by pericentric inversions that followed chromosomal fissions. Interestingly, one species, A. grahami, showed an extensive chromosome number polymorphism (2n = 30~37), probably due to multiple Robertsonian fission events in metacentric macrochromosomes (Blake 1986). The high chromosomal number found in A. nebuloides (2n = 42) also seems to be due to fission events (Figure 4).…”

“…Since then, scientific interest has shifted to other fields of study, and the chromosomal evolution of anoles has not been further investigated. Indeed, only a few papers in this regard were published from 1980 to the present (Blake 1986;Brandley et al 2006;Castiglia et al 2010). However, anoles exhibit remarkable inter-and intraspecific variations in chromosome number and morphology as well as in the presence/absence of heteromorphic sex chromosomes.…”

Occurrence of B chromosomes in lizards: a review

“…There were no mitotic spreads available for this individual. Blake (1986) studied the chromosomal variations (2n = 30-37) due to different rearrangements and number of macro-and microchromosomes, including accessory micros, in several populations of Anolis grahami from Jamaica. In two specimens, an extra pair of microchromosomes was present in some meiotic metaphase I spreads.…”