Cytogenetic Characterization of a Population of <b><i>Acanthodactylus lineomaculatus</i></b> Duméril and Bibron, 1839 (Reptilia, Lacertidae), from Southwestern Morocco and Insights into Sex Chromosome Evolution

Abstract

Acanthodactylus lineomaculatus is now regarded as an ecotype of A. erythrurus with which it has been recently synonymized. Despite the wide range of A. erythrurus, karyological data for this species are scarce and limited to classical cytogenetic studies carried out in individuals from only 2 locations (central Spain and Spanish enclave of Melilla on the northwestern Mediterranean Moroccan coast). Here, for the first time, we cytogenetically characterized individuals of A. lineomaculatus from the southwestern Moroccan Atlantic coast with the aim to increase the karyological knowledge of this wide-ranging species and to assess if any chromosomal changes can be found in this ecotype in comparison to other populations of this species. The diploid number of the individuals investigated is 2n = 38 which is typical of most lacertids. Active NORs were located telomerically in a medium-small pair of chromosomes, and no inactive NORs were detected. C-banding revealed an intensely heterochromatic W chromosome composed of AT-rich (centromere and long arm telomeric region) and GC-rich (most of the long arm) regions, with extended interstitial telomeric sequences. These telomere-like repeats occupy the GC-rich heterochromatin of the W. The DNA composition of the W represents a trait distinguishing A. lineomaculatus (southwestern Morocco) from A. erythrurus from Spain that possess a DAPI-positive (AT-rich) W chromosome. In conclusion, these results add further evidence to the remarkable karyotype conservation in lacertid lizards, although differences in NOR location and in W chromosome structure among populations could suggest an incipient speciation mediated by chromosome changes in this wide-ranging lizard species.

Characterization of a satellite DNA in the genera Lacerta and Timon (Reptilia, Lacertidae) and its role in the differentiation of the W chromosome

“…() for L. agilis , and in the W of the Timon species investigated. The enrichment in telomeric‐like repeats of the sex heterochromosome has been recorded also in the lacertid A. lineomaculatus (Giovannotti et al., ), in the agamid lizard Pogona vitticeps (Young, O'Meally, Sarre, Georges, & Ezaz, ), and in the gecko Underwoodisaurus milii (Pokorná, Rens, Rovatsos, & Karatochvíl, ).…”

“…A, C, TA, CAA, CAG, CAT, GAC, GAG, TAA, TAC) or its centromeric region (repeated motif: CA, GC, GA), whereas in the latter species Giovannotti et al (2017) observed and enrichment in telomeric-like sequences of the W-chromosome heterochromatin. Also in the lacertine Lacerta agilis, the (micro-)W chromosome was found to be enriched in telomeric repeats (Matsubara et al, 2015b;Srikulnath et al, 2014).…”

“…In the former species, Pokorná, Kratochvìl, and Kejnovsky () observed an enrichment in some microsatellite sequences on either the whole W chromosome (repeated motif: A, C, TA, CAA, CAG, CAT, GAC, GAG, TAA, TAC) or its centromeric region (repeated motif: CA, GC, GA), whereas in the latter species Giovannotti et al. () observed and enrichment in telomeric‐like sequences of the W‐chromosome heterochromatin. Also in the lacertine Lacerta agilis , the (micro‐)W chromosome was found to be enriched in telomeric repeats (Matsubara et al., ; Srikulnath et al., ).…”

Chromosome Painting Does Not Support a Sex Chromosome Turnover in Lacerta agilis Linnaeus, 1758

“…Furthermore, W chromosomes of similar size and repeat content are characteristic for other species of Lacerta : all studied Lacerta species including L. agilis have telomeric repeat accumulation in the W chromosome, and share a monophyletic W-specific subfamily of the IMO-TaqI satellite DNA [Giovannotti et al, 2018]. Considering the fact that the sequence content of the W chromosomes in the related genera Iberolacerta and Timon is different from that of Lacerta , as shown by CGH [Rojo Oróns, 2015], and that the W-specific repetitive DNA can also differ in different populations of the same species [Giovannotti et al, 2017a], the sharing of the same repetitive DNAs by the W chromosomes of different Lacerta species seems to indicate stability and homology for the ZZ/ZW system within this genus.…”

Chromosome painting does not support a sex chromosome turnover in Lacerta agilis Linnaeus, 1758

“…Furthermore, W chromosomes of similar size and repeat content are characteristic for other species of Lacerta : all studied Lacerta species including L. agilis have telomeric repeat accumulation on the W chromosome, and share a monophyletic W-specific subfamily of the IMO-TaqI satellite DNA [Giovannotti et al, 2018]. Considering the fact that the sequence content of the W chromosomes in the related genera Iberolacerta and Timon is different from that of Lacerta , as shown by CGH [Rojo Oróns, 2015] and that W-specific repetitive DNA can also be different in different populations of the same species [Giovannotti et al, 2017], the sharing of the same repetitive DNAs by the W chromosomes of different Lacerta species seems to indicate stability and homology for the ZZ/ZW system within this genus.…”