= Aspidoscelis
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<Aspidoscelis> is a <taxonomic genus> of whiptail <lizards> in <Teiidae>. It contains both sexually reproducing <species> and all-female lineages that reproduce by <parthenogenesis>. This variation makes a closely related set of animals useful for studying how reproduction and chromosome organization interact.<Sister chromosome pairing maintains heterozygosity in parthenogenetic lizards by Aracely A. Lutes and others>[Abstract, sexual and parthenogenetic whiptails]{ref}
In a 2011 experiment, researchers crossed a triploid parthenogenetic female lineage with males of a sexually reproducing lineage. The resulting four-copy <hybrid (biology)> offspring were checked with molecular and chromosome measurements. Some female offspring themselves reproduced by <parthenogenesis>, establishing laboratory lineages able to reproduce without repeating the original cross.<Laboratory synthesis of an independently reproducing vertebrate species by Aracely A. Lutes and others>[Abstract and Results, tetraploid hybrids and independent reproduction]{ref}
A chromosome-set calculation clarifies the change: an unreduced egg carrying three sets can combine with a sperm carrying one set to make a four-set offspring, $3n+n=4n$. This is <tetraploidy>, rather than merely four copies of one selected <gene>. Producing one viable <hybrid (biology)> is also different from demonstrating that its descendants can reproduce. The experiment tested both steps, linking the immediate effects of a cross to the persistence of a new reproductive lineage.
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