Thanks for the link. I will admit, right off the bat, that I cringed while reading that abstract.
"In most rose species only one ploidy level is observed. However, some can have different ploidy levels. For example R. chinensis can be di-, tri- or tetraploid, while R. acicularis can be tetra-, hexa- or octoploid."
As far as anyone can determine, Rosa chinensis
Jacq. was based on a garden variety rose derived from two or more ancestral species. Even the Crimson China (Slater never saw it) carried genes derived from R. multiflora
and R. luciae,
among others. We really should stop confusing groups of garden plants with formal species. China roses are not Rosa chinensis,
just as Rugosas are nor R. rugosa
and Gallicas are not R. gallica.
And it's not just roses that get mistreated in this way. The German Irises are not derived from Iris germanica,
despite what some Catalog writers have claimed.
Is Rosa acicularis
really "tetra-, hexa- or octoploid?" Did the speaker forget the diploid R. acicularis nipponensis
Unlike so many other botanists, Hurst (1932) was able to consider more than a handful of traits at one time:
"... we have the interesting case of Rosa acicularis,
which is said by different cytologists to have diploid, tetraploid, hexaploid and octoploid forms. A critical taxonomic diagnosis of the material used shows clearly, however, that the original R. acicularis
of Lindley is octoploid and includes two distinct genetical species with septets AACCDDEE and BBCCDDEE, while the American hexaploid "acicularis" are either R. Bourgeauiana
Crép. which is BBCCDD, or R. Sayi
Schwein., which is CCDDEE. The tetraploid "acicularis nipponensis" of Willmott (non Crép.) found in the Kew collection is a subspecies of R. pendulina
L., which is DDEE, while the original diploid R. acicularis nipponensis
of Crépin is a subspecies of R. rugosa
Thunb., which is CC."
For those not familiar with Hurst's shorthand, each of the letters, A through E, represents a set of 50 traits that Hurst found to hold together in species around the world. For example, The A group includes the Synstylae, Indicae and Banksiae.
Hurst's terminology is out-of-date. Back in the 1920s, when he got started, he assumed (as almost everyone else did) that the identifying traits of a species must involve genes scattered among the seven chromosomes of the haploid set. Since then, however, we have a better (though imperfect) understanding of "supergenes".