Comparative Chromosome Painting and NOR Distribution Suggest a Complex Hybrid Origin of Triploid Lepidodactylus lugubris (Gekkonidae)

Abstract

Parthenogenesis, unisexuality and triploidy are interesting but poorly studied phenomena occurring in some reptile species. The mourning gecko (Lepidodactylus lugubris) represents a complex of diploid and triploid parthenogenetic mostly all-female populations (males occur quite rarely) widely distributed in coastal areas of the Indian and Pacific Oceans. Here, we study karyotypes of a male and two female L. lugubris (LLU) triploid individuals (3n = 66) using comparative painting with Gekko japonicus, Hemidactylus turcicus and H. platyurus chromosome specific probes to visualize the homologous regions and to reveal genus specific rearrangements. Also, we applied a 28S ribosomal DNA probe and Ag-staining to detect nucleolus organizer regions (NORs). Our results suggest that the karyotype of L. lugubris underwent a chromosome fission and a fusion after its divergence from a common ancestor of the Gekko-Hemidactylus group. The NORs were found to be located on one out of three homologs on each of LLU8, LLU15 and LLU18, thus further confirming a hybrid origin of triploid individuals. It seems that three different bisexual populations might have contributed to the origin of this triploid parthenogenetic population. We postulate that the heterozygosity in NOR localization is maintained in the triploid clone studied by the absence of recombination as described in whiptail lizards. The pattern of NOR localizations and homologous regions in males and females, as well as the absence of other detectable karyotypic differences, suggest that males arise spontaneously in all female populations and do not arise from independent hybridizations with different species.

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

“…The number and chromosomal distribution of NOR sites have been traditionally regarded as of taxonomical relevance and used many times for taxonomical inferences [see Odierna et al, 1987;Olmo et al, 1990 and references therein;Caputo et al, 2009;Trifonov et al, 2015]. Silver staining revealed a single NOR site, located on a medium-small [MS sensu Olmo et al, 1990] pair of chromosomes in telomeric position.…”

Segmental paleotetraploidy revealed in sterlet (Acipenser ruthenus) genome by chromosome painting

“…Although it was proposed that the 102-chromosomal genome of the South American red vizcacha rat ( Tympanoctomys barrerae ) resulted from tetraploidization [ 42 ], subsequent chromosome painting data clearly demonstrated that all chromosomal segments are present in diploid state [ 43 ]. On the other hand, chromosome painting turned out to be very useful in confirmation of triploidy in some lizards [ 44 ]. As most fish genomes have not been involved yet in chromosome painting experiments, future molecular cytogenetic works may shed light onto the level of ploidy in their genomes.…”

Isolating Chromosomes of the Komodo Dragon: New Tools for Comparative Mapping and Sequence Assembly

“…Similarly, chromosome-specific DNA was used to produce paints which were employed for cross-species chromosome painting experiments in several species of reptiles [Kasai et al, 2012b;Johnson Pokorná et al, 2015;Trifonov et al, 2015]. Additionally, chicken painting probes hybridized to reptile chromosomes revealed a strong conservation of avian sex chromosomes and autosomes in a number of squamates [Pokorná et al, 2011[Pokorná et al, , 2012.…”