Acta Herpetologica - 2006 - 2 - Standar Karyotypes of Two Populations of the «Scincus scincus» Complex from Tunisia and Morocco (Reptilia : Scincidae) Standard karyotypes of two populations of the Scincus scincus complex from Tunisia and Morocco (Reptilia: Scincidae) Mohsen Kalboussi 1, Gennaro Aprea 2, Andrea Splendiani 3, Massimo Giovannot- ti 3, Vincenzo Caputo 3,4 1 Département des Sciences Biologique, Faculté des Sciences de Tunis, Tunisia 2 Dipartimento di Biologia Evolutiva e Comparata, via Mezzocannone 8, I-80134 Napoli, Italy 3 Istituto di Biologia e Genetica, Università Politecnica delle Marche, via Brecce Bianche, I-60131 Anco- na, Italy; 4 Corresponding author. E-mail: v.caputo@univpm.it Abstract. A study on chromosomes of two Scincus populations attributed to S. scin- cus and S. albifasciatus was carried out by conventional Giemsa staining. Both samples showed the same diploid number of 2N = 32 and identical chromosome morphology. Therefore, these populations seem to be lacking in chromosome changes that could act as barriers to gene flow. However, because speciation in lizards is not always asso- ciated with chromosome repatterning, the taxonomic status of “scincus” and “albifas- ciatus” forms remains unsettled. Keywords. Karyotypes, Scincus scincus, Tunisia; Morocco. The scincid lizard genus Scincus Laurenti, 1768 is a clearly-defined group of species adapted to life in areas of loose, usually wind-blown sand. This taxon is distributed from the Western Sahara Desert and its borders, eastwards to Arabia, southern Iraq and south- western Iran. North African populations fall into two groups, which may represent largely allopatric species, namely S. scincus (Linnaeus, 1758) in the East and S. albifasciatus Bou- lenger, 1890 in the West. However, according to Arnold and Leviton (1977), evidence for specific status is not conclusive because resting on an unsatisfactory sample base; in addi- tion, as sympatric populations of the two presumed species have not been found so far, it is not possible to evaluate whether gene flow is still acting or not. In the years following Arnold and Leviton’s review, the taxonomic status of the Saha- ran Scincus populations remained unsettled. Faunal works and checklists by Bons and Geniez (1996), Schleich et al. (1996), and Geniez et al. (2000) variously regarded them as separated species or subspecies of S. scincus, but without further review of evidence. Final- ly, Caputo et al. (1994) compared karyotypes of S. scincus from Egypt and of S. hemprichii Wiegmann, 1837 from the Arabian Peninsula, calling for a full taxonomic re-evaluation of the group by use of non-morphologic characters like chromosomes and molecular mark- ers. In an attempt to clarify the status of the S. scincus complex in North Africa, we have Acta Herpetologica 1(2): 127-130, 2006 128 M. Kalboussi et alii studied the chromosome complements of two populations attributed to the scincus and albifasciatus forms; we have also reviewed and compared the karyological data reported in literature for these Palaearctic skinks. The karyotypes analysed come from two adult males and one adult female of Scin- cus albifasciatus laterimaculatus Werner, 1914 from south-eastern Morocco (Hamada du Dra, environs of Zagora) and from three females of S. scincus cucullatus Werner, 1914 from southern Tunisia (environs of Douz). Voucher specimens are deposited in the col- lection of V. Caputo (Faculty of Sciences, Ancona, Italy). The animals were injected with colchicine (0.05 mg/ml; 0.01 ml/g body weight) 1 hour before dissection. Metaphase plates were obtained from intestine, bone marrow and ovarian or testicular tissue. Chromosome number and standard morphology were determined by conventional Giemsa staining at pH 7.0. Chromosome nomenclature was in accordance with Levan et al. (1964). Due to the scarcity of metaphases, no banding was possible and we were able to obtain only standard karyotypes. Diploid chromosome complements and relative Giemsa-stained metaphases are repre- sented in Fig. 1. The specimens analysed of the two presumptive species of Scincus showed identical 2N = 32 standard karyotypes, in which the first two pairs of metacentric chro- mosomes were considerably larger than the remaining 14. The latter decreased gradually in size, and therefore it was not possible to distinguish between macro- and micro-chro- mosomes. The chromosomes of the 3rd pair were also metacentric, whereas that of the remaining 13 pairs were subtelocentric. No heteromorphic chromosomes were distin- guishable. The karyotype of S. scincus scincus (Linnaeus, 1758) from Egypt (Caputo et al., 1994) is identical to those described in the present paper, whereas that of S. hemprichii Fig. 1. Karyotypes (right) and Giemsa-stained metaphase plates (left) of Scincus albifasciatus laterimacula- tus from Morocco (top) and S. scincus cucullatus from Tunisia (bottom). Scale bar = 10 μm 129Standard karyotypes of two populations of the Scincus scincus (Branch, 1980) differs in having two additional pairs of small acrocentric chromosomes (2N = 36) (Fig. 2). The karyological data presented here and the comparison with those reported in liter- ature evidence a uniform karyotype structure, both in diploid number and in chromosome morphology, between populations attributed to subspecific (cucullatus and scincus, within S. scincus) or specific (S. scincus versus S. albifasciatus) taxa (e.g., Schleich et al., 1996; Geniez et al., 2000). So, these populations seem to be lacking in chromosome changes that could act as reproductive barriers. However, because speciation in lizards is not always associated with chromosome repatterning (see King, 1981), and considering that the 2N = 32 karyotype is plesiomorphic for skinks (Caputo et al., 1994), the lack of karyotypic differentiation does not necessarily indicate that the “scincus” and “albifasciatus” forms belong to the same biological species. Therefore, further analyses should be performed in order to clarify the taxonomic status of the Scincus scincus complex in North Africa. The karyotype of this latter closely resembles that of S. hemprichii (Branch, 1980), differing for two less small acrocentric chromosomes. Probably, the 2N = 36 karyotype of S. hemprichii represents an apomorphic condition derived by fissions from the complement with 2N = 32 chromosomes, considered the ancestral skink karyotype state (Caputo et al., 1994). This hypothesis is also in line with that of Arnold and Leviton (1977), according to which S. scincus is the most primitive constituent of the genus. The speciation of S. hemprichii and the differentiation of its karyotype would have been promoted by the Plio-Pleistocene climatic fluctuations (Suc, 1984, 1989). Indeed, during the most mesic climatic periods, the pluvial phases in the Saharan-Arabian region would have caused the isolation into a separated arid refugium of a small skink population where the genetic drift favoured the fixation of a new chromosome set. The present limited geographic range of S. hemprichii, marginal to the larger distribution of S. scincus, seems to sustain this hypothesis. Fig. 2. Karyotype of Scincus hemprichii (from Branch, 1980). 130 M. Kalboussi et alii REFERENCES Arnold, E.N., Leviton, A.E. (1977): A revision of the lizard genus Scincus (Reptilia: Scinci- dae). Bull. Br. Mus. Nat. Hist. (Zoology) 31: 187-248. Bons, J., Geniez P. 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