title: Widespread failure to complete meiosis does not impair fecundity in parthenogenetic whiptail lizards.
abstract: Parthenogenetic species of whiptail lizards in the genus Aspidoscelis constitute a striking example of speciation by hybridization, in which first-generation hybrids instantly attain reproductive isolation and procreate as clonal all-female lineages. Production of eggs containing a full complement of chromosomes in the absence of fertilization involves genome duplication prior to the meiotic divisions. In these pseudo-tetraploid oocytes, pairing and recombination occur exclusively between identical chromosomes instead of homologs; a deviation from the normal meiotic program that maintains heterozygosity. Whether pseudo-tetraploid cells arise early in germ cell development or just prior to meiosis has remained unclear. We now show that in the obligate parthenogenetic species A. neomexicana the vast majority of oocytes enter meiosis as diploid cells. Telomere bouquet formation is normal, but synapsis fails and oocytes accumulate in large numbers at the pairing stage. Pseudo-tetraploid cells are exceedingly rare in early meiotic prophase, but they are the only cells that progress into diplotene. Despite the widespread failure to increase ploidy prior to entering meiosis, the fecundity of parthenogenetic A. neomexicana is similar to that of A. inornata, one of its bisexual ancestors.
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors: Aracely A
authors: AA
authors: Newton
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors: Robert R
authors: RR
authors: Schnittker
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors: Zulin
authors: Z
authors: Yu
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors: Sarah S
authors: SS
authors: Munday
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors: Diana P
authors: 0000-0003-4892-1485
authors: DP
authors: Baumann
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
authors: William B
authors: WB
authors: Neaves
authors: Stowers Institute for Medical Research, Kansas City, MO 64110, USA peb@stowers.org.|Howard Hughes Medical Institute, Kansas City, MO 64110, USA.|Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
authors: Peter
authors: P
authors: Baumann
mesh_terms: D000818:Animals; D023902:Chromosome Pairing / Q000502:physiology; D004247:DNA / Q000235:genetics / Q000378:metabolism; D005260:Female; D005298:Fertility / Q000235:genetics* / Q000502:physiology; D008116:Lizards / Q000196:embryology*; D008540:Meiosis / Q000235:genetics*; D009865:Oocytes / Q000254:growth & development; D010312:Parthenogenesis / Q000502:physiology*; D016615:Telomere / Q000378:metabolism; D057891:Tetraploidy
chemical_list: D004247:DNA
keywords: Aspidoscelis; Endoreplication; Meiosis; Parthenogenesis; Synaptonemal complex