DNA and chromosome evolution in lacertid lizards (original) (raw)
Related papers
Further data on sex chromosomes of Lacertidae and a hypothesis on their evolutionary trend
Amphibia-Reptilia, 1993
Sex chromosomes were studied in eight species of laccrtid lizards using C-banding, G-banding and restriction enzyme treatment. All of the species showed female heterogamely. The W chromosome was a microchromosome in Lacerta graeca and Ophisops degans. Two types of W were found in Lacerta vivipara; in specimens from The Netherlands it was metacentric, whereas in specimens from Russia it was acroccntric or subteloccntric. The W chromosome was homomorphic or nearly homomorphic but completely C-banded and hetcrochromatic in Lacerta agilis, Podarcis hispanica, Algyroides moreoticus and A. nigropunctatus. In was only possible to find sex chromosomes using the G-banding method in Podarcis sicula. The results obtained, together with data in the literature, suggest that sex chromosomes are likely to be present in all Lacertidae and that their differentiation took place repeatedly and independently in different taxa within the family. A model for sex chromosome evolution in the family, in which the starting point was the heterochromatization of the W chromosome, is proposed.
Heterochromatin and genome composition in lacertid lizards
Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 1988
We have previously reported (Odierna et al., 1985; Olmo er 4/., 1986) a wide variability in quantity and location of constitutive heterochromatin in the karyotypc of many iacertid lizards. The variability is lourd between species and in addition between subspecies or populations of the same species, and it is the most signilìcant (and in many cases, the only) chromosomal reaffangemeDt observed in these reptiles (Olmo, 1986). lt is well known that C-bands are usually associated with "satellite"Jike highly repetitive DNA sequences (John and Miklos, 1979), and a correlation between the amount of heterochromatic DNA and highìy repetitive DNA has been observed ìn various organisms (John and Miklos, 1979; Ginatu!,ira et ol., 1982). Since in the lacertid Podarcrs .ticula sicula. the percentage ol heterochromatin approximates that of highly repeated DNA (Odierna el a/., 1985), we have started to investigate the composition of constitutive heterochromatin in various species of this lamily.
The karyotype of Lacerta horv�thi (Reptilia, Sauria, Lacertidae)
Genetica, 1989
The chromosomes of Lacerta horvfthi have been studied by means of conventional, C-banding, and silver-NOR techniques. The karyotype of this species, characterized by 36 acrocentric macrochromosomes, lacks the typical pair of microchromosomes shared by all other lacertid lizards. It is hypothesized that the microchromosomes could have been translocated to the large elements of the karyotype. The occurrence of such a rearrangement in the chromosome complement ofL. horvhthi underlines its isolation from the other species of the subgenus Archaeolacerta. The C-banding analysis evidences the existence of a female sex heteromorphism in which the W-chromosome has the same shape and size of the Z, but differs from it in being completely heterochromatic. The nucleolar organizer regions (NORs) are located on a pair of medium size chromosomes in subtelomeric position, where the standard Giemsa-staining reveals secondary constrictions.
Preliminary chromosome studies of some Nevada Test Site lizards
Among the approximately 60 species of the lizard genus Sceloporus, there is much karyotypic diversity, resulting primarily from the fixation of "Robertsonian rearrangements" (centric fusions and fissions; Hsu and Mead, 1969; Jackson, 1971). Diploid (2n) chromosome numbers vary from 22 to 46 (Cole, 1970, 1971; Hall, 1973), a range exceeding that known for any other lizard genus. Because comparable variation has been detected in several groups of vertebrates, including other lizard genera (Gorman and Atkins, 1968; Matthey and van Brink, 1960) and rodents (review by Nadler, 1969), and in many invertebrates, evolutionists are becoming increasingly concerned with the role of karyotypic changes in animal speciation (White, 1969; Mayr, 1969, 1970). To investigate relationships between karyotypic diversification and speciation, Hall has undertaken a survey of chromosomal variation in Sceloporus and related genera, seeking particularly to identify intermediate evolutionary stages. Of 48 species of Sceloporus examined, all but one, the Mexican form S. grammicus, are karyotypically monomorphic, at least for Robertsonian mutations of the autosomes. An analysis of 1200 individuals of S. grammicus has revealed extensive chromosomal diversity at several levels of population structure, including the occurrence of rare individual variants, polymorphism, and the fixation of different Robertsonian modifications in parapatrically or allopatrically distributed populations. Chromosome numbers vary geographically from 2n = 31 to 2n = 46. The available data on karyotypic variation and geographic and ecologic distributions of populations suggest that the morphologically defined taxon S. grammicus (Smith, 1939; Smith and Laufe, 1945) actually represents several semispecies or cryptic species in early stages of differentiation. In the present study we have examined patterns of karyotypic and genic variation in a zone of contact between two karyotypically distinctive populations of grammicus to determine the extent of their genetic isolation. This research has implications for the systematic problem of defining species limits in the grammicus complex and contributes to an understanding of the evolutionary significance of parapatric hybridization.
Evolution of sex-chromosomes in lacertid lizards
Chromosoma, 1987
The occurrence and form of sex chromosomes were investigated with the aid of C-banding and 4'-6-diamidino-2-phenylindole (DAPI) staining in 13 species of lacerrid lizards. The results obtained show the presence in five species of a female heterogamety in which the two sex chromosomes have the same shape and size, but the W differs from the Z in being almost entirely heterochromatic. This condition is clearly similar to that found in some snakes and considered to be an early stage of differentiation of sex chromosomes by . A more evolved condition may be that found in three other species in which the W is distinctly smaller than the Z. A third situation is that found in all Podarcis species which, even though they are considered to be among the more evolved species in the family, possess two sex chromosomes that are indistinguishable. In general, the situation in lacertids may be compatible with the hypothesis of sex chromosome evolution put forward by . However a differentiation mechanism of this kind does not seem to be well established in lacertids, and is probably not the only mechanism that is in operation in this family.
1990
Even if the common lizard Lacerta vivipara and endemic Lucerta andreanskyi from Moroccan Grand Atlas have the same mother species, the two species are defmitely not closely related in present-day nature, where L. vivipara stands at variance from all other lacertids in terms of cytogenetics. The use of replication banding, C-bands and R-bands has allowed for the identification of all chromosome pairs and two sex chromosomes in L. andreanskyi. Its karyotype is typical of Lacertidae. The W chromosome, characterized by late replication, is nevertheless of a type previously unknown in the family. The comparison of Z and W chromosomes by different methods of chromosome banding indicates little homology between them, if any. The replication study has shown that there is no dosage compensation for the Z chromosome in (homogametic) males. That genetic inactivation precedes chromosomal mutations in non-vivipara lacertid evolution of the odd sex chromosome is suggested.
Rendiconti Lincei-scienze Fisiche E Naturali, 1991
The chromosome complement of Lacerta mosorensis was analyzed by means of conventional techniques in both somatic and spermatogonial metaphases. This species exhibits a typical lacertid karyotype, being characterized by the diploid number 2n = 38 (Fundamental Number = 38). In males the analysis of somatic metaphases reveals 36 acrocentric macrochromosomes and 2 microchromosomes (36 MI + 2m). In females all the examined somatic metaphases are characterized by 35 acrocentric macrochromosomes and 3 small dot-shaped microchromosomes (35 MI + 3 m). This result clearly indicates that in Lacerta mosorensis the female is heterogametic. The sex-determining mechanism is of the ZZ/ZW type; in the female karyotype the Z-chromosome is a large sized macrochromosome, while the W-chromosome is equal in size to the two micro-autosomes. Il cariotipo di Lacerta mosorensis è stato studiato utilizzando tecniche convenzionali di preparazione dei cromosomi da midollo osseo e testicoli. Il corredo cromosomico di questa specie è quello caratteristico dei Lacertidi: L. mosorensis è infatti caratterizzata da numero diploide 2n = 38 (Numero Fondamentale = 38). Nei maschi l’analisi delle metafasi somatiche rivela la presenza di 36 macrocromosomi acrocentrici e 2 microcromosomi (36 MI + 2m). Le metafasi somatiche delle femmine sono invece caratterizzate costantemente da 35 macrocromosomi acrocentrici e 3 microcromosomi (35 MI + 3 m). Ciò indica chiaramente che inLacerta mosorensis esiste eterogametia femminile. Il meccanismo di determinazione del sesso è del tipo ZZ/ZW. Il cromosoma Z del cariotipo femminile è un macrocromosoma di grandi dimensioni, mentre il cromosoma W è piuttosto piccolo ed ha dimensioni simili a quelle dei due micro-autosomi.