Widespread failure to complete meiosis does not impair fecundity in parthenogenetic whiptail lizards
نویسندگان
چکیده
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.
منابع مشابه
Chromosome inheritance in parthenogenetic lizards and evolution of allopolyploidy in reptiles
ABOUT one percent of the 3,000 species of lizards in the world have all-female populations in which reproduction seems to be by true parthenogenesis (as opposed to gynogenesis or hybridogenesis). For some species, no males have ever been found at any localities. For a few species, all-female populations occur at some localities, bisexual populations at others. (In unisexual populations all norm...
متن کاملDifferential effects of testosterone and progesterone on the activation and retention of courtship behavior in sexual and parthenogenetic whiptail lizards.
Both testosterone (T) and progesterone (P) facilitate the expression of male-typical sexual behavior in a variety of animals, including rodents and lizards. In two species of whiptail lizards, Cnemidophorus inornatus and C. uniparens, both hormones elicit the full repertoire of courtship behavior. However, the relative efficacy of the two hormones is unknown. In Experiments 1 and 2 we assessed ...
متن کاملSpecies differences in the regulation of tyrosine hydroxylase in Cnemidophorus whiptail lizards.
Evolution of behavioral phenotype involves changes in the underlying neural substrates. Cnemidophorus whiptail lizards enable the study of behavioral and neural evolution because ancestral species involved in producing unisexual, hybrid species still exist. Catecholaminergic systems modulate the expression of social behaviors in a number of vertebrates, including whiptails, and therefore we inv...
متن کاملAndrogenic regulation of steroid hormone receptor mRNAs in the brain of whiptail lizards.
Sex and species differences in androgenic regulation of steroid hormone receptor mRNAs were examined in the diencephalon of two species of whiptail lizards: Cnemidophorus inornatus is a sexual species and the direct evolutionary ancestor to Cnemidophorus uniparens, an all-female parthenogenetic species. Lizards were gonadectomized and treated with different doses of either aromatizable testoste...
متن کاملSex differences in estrogen-induced progesterone and estrogen receptor mRNA in the ventromedial hypothalamus of hatchling whiptail lizards.
The ventromedial hypothalamus (VMH) is an important neural locus for the control of female-typical sexual behavior in vertebrates, and exogenous estrogen stimulates a strong increase in progesterone receptor (PR) in the VMH of adult females. Estrogen also regulates its own receptor (ER), though the direction of the response varies from species to species. In rodents and whiptail lizards, males ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره 143 شماره
صفحات -
تاریخ انتشار 2016