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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.^[ref]

In a 2011 experiment, researchers crossed a triploid parthenogenetic female lineage with males of a sexually reproducing lineage. The resulting four-copy hybrid 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.^[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 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.

A cultivar is a selected assemblage of cultivated plants that remains distinguishable, sufficiently uniform and stable in specified characteristics when maintained by appropriate plant propagation. The characteristics may concern form, colour, flowering or other useful traits. A cultivar is a named cultivated selection, rather than simply any individual growing in a garden.^[ref]

The phrase “appropriate propagation” matters. Some cultivars are maintained by vegetative propagation, while others can be maintained through seeds or a repeatable hybrid cross. A cultivar therefore need not consist of just one plant clone.^[ref]

For an illuminating example, suppose a selected plant has a distinctive flower colour. Producing more plants is insufficient if their flowers lose that distinguishing trait. The propagation procedure must retain the relevant combination of characteristics. Conversely, variation in an unselected feature need not invalidate the selection: “uniform” concerns the characteristics that distinguish the cultivar, not absolute identity in every measurable property.

A rose is a flowering plant of Rosa, within Rosaceae. The term also refers to its flower. Roses are typically shrubs or climbing plants, and many cultivated forms have a hybrid origin and are selected for floral traits. Their flowers have a characteristic cup-shaped hypanthium, with numerous stamens around the rim and many separate carpels inside.^[ref]

After successful reproduction, the hypanthium can enlarge into a rose hip. The small dry fruits enclosed within it are achenes; the fleshy outer structure is not one giant seed or a single enlarged ovary. Cutting a mature hip lengthwise and locating the individual achenes provides a direct anatomical comparison with a strawberry, whose achenes sit outside its fleshy receptacle.^[ref]

This comparison explains a useful feature of Rosaceae: related plants can produce conspicuously different edible or seed-bearing structures by enlarging different tissues and arranging their carpels differently. The family relationship is consequently richer than resemblance between petals alone.