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Evolution of sex chromosomes and karyotypes in iguanas (Squamata: Pleurodonta)
Altmanová, Marie ; Kratochvíl, Lukáš (advisor) ; Kejnovský, Eduard (referee) ; Zrzavá, Magda (referee)
Evolution of sex chromosomes and karyotypes in iguanas (Squamata: Pleurodonta) PhD Thesis Marie Altmanová Abstract This PhD thesis is composed of five published articles and one manuscript, and is focused on the evolution of the sex chromosomes and karyotype of the iguanas (Pleurodonta). Based on our primary research of available data, only male heterogamety (XX/XY) with ancestral karyotype 2n = 36 chromosomes was recorded in iguanas. However, in many species sex chromosomes have not been uncovered by classical cytogenetics, probably due to their homomorphy. The partially-known X chromosome content of Anolis carolinensis allowed us to compare the relative gene doses of X-specific genes between male and female of representatives of all iguana families, and to reveal homologous and well-differentiated sex chromosomes across all iguanas, with the exception of basilisks. Thus, due to the comparable age with sex chromosomes of mammals and birds, the results put into question the importance of endothermy for the formation of stable sex chromosomes. The striking feature of the iguanas is the relatively frequent occurrence of multiple sex chromosomes in their karyotypes. Using the ancestral state analysis of the type of sex chromosomes, it has been found that these multiple sex chromosomes developed at least twelve...
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Evolution of karyotype and sex determination in iguanas (Squamata: Pleurodonta)
Altmanová, Marie ; Kratochvíl, Lukáš (advisor) ; Zrzavá, Magda (referee)
Squamate reptiles in general possess an unusual variability in karyotype and sex determining mechanisms. However, in these two aspects, iguanas (Pleurodonts) are considered as a relatively conservative group of lizards. So far only genotypic sex determination with male heterogamety has been detected in this lineage. However, the sex chromosomes have not been revealed in many species by classical cytogenetics, probably due to their homomorphy. Significant variability in karyotype was observed only in the species-rich genera Anolis, Sceloporus and Liolaemus. The aim of this thesis was to investigate the genome of available species from the main iguanid lineages using classical and molecular cytogenetic methods. As well as finding the karyotype characteristics, which may represent synapomorphies of main iguanid lineages, the other aim was to try to identify sex chromosomes. This study confirmed previously published karyotypes of 13 species and established new descriptions of karyotype for eight species. The chromosomes of all studied specimens were examined by methods of classical and molecular cytogenetics, 21 species covering eight iguanid families were analysed in this thesis. The majority of studied species shared the apparently ancestral karyotype of the group, with diploid chromosome number...
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