Apparent variation of physical characteristics of individual plants within a large population of any particular species group have led some botanists to name separate species or subspecies which some other botanists have later said are nothing more than slight variations within the group.
How far should variation be permitted before the breeding should be considered to fall below “100% true”?
Has testing found that genetic prints of all members of a species are identical?
All individuals are true to species if pollinated by another same sp individual. Individual differ but allways keep sp identity. Amount of viable and strong if not allways 100% is far far above those of modern roses progenies.
Species that have a large dispersion and some isolation are subject to genetical drift that may be considered as speciation or not.
There are sps whose members are totally identical, in fact they are clones as then fecondation is bypassed. As for clones it is risky as such uniformity preclude evolution when needed in a changing environment.
In defining what a species one can quickly bog down in a quagmire, especially with plants and most especially with roses. Is it really necessary to have a definition, anyway?
My crystal ball says that the concept of heirarchical taxonomy is becoming obsolete and is already being replaced by metrics that index a cultivar’s position on a multidimensional relatedness network using DNA sequence data. Every cultivar will have a unique set of vector indices that plot its position on the relatedness network. Cultivars which are very similar (share large numbers of similar genes) will cluster together. Likewise, these clusters will, in turn, form clusters of their own, and so on. Rather than discussing species, genera and families, we will soon refer to first order, second order and third order clusters.
The advantage of this system is that 1.) it can accomodate hybrids (and all roses are hybrids, ‘species’ included), and 2.) there can be different relatedness networks for different traits. We have already seen the foundations for the latter in the work by Scalliet, Piola and others on o-methyl transferases in roses.
Anyway, don’t get too wrapped up in trying to define a species because it’s a futile task no matter what the future holds.
Thank you, Pierre, for your interesting observation of the functional need of evergreen species for more disease resistant foliage and the concomitant lack of need in short-season species. I’m also interested in the suggestion that evergreen-ness is an older quality and deciduousness a more recent trait. All of that makes good sense to me.
I also agree with Don. Thinking of plant - and rose - species as a statistical concept enhances rather than detracts from our understanding of them. Our early plant biologists didn’t know that species require a different kind of analysis and description than cultivars. Those guys were great collectors of one of everything. Since each species has a greater or lesser range of variability, basing a description based on a single individual is inherently inaccurate. If we accept that that at the ends of the bell curve (or the individuals outside the Venn diagrams) are either aberrant individuals or hybrids, we’ll have a better idea of what we’re working with. Unfortunately, many rose species descriptions have been derived in exactly that way, from a single example, sometimes in an herbarium. To no one’s wonderment, such individuals have never been seen since. This is all theoretical, of course, since we don’t have access to adequate germplasm of some of the most interesting species to really know the range of variation. Worse, in many cases, the descriptive material is locked away in obscure pay-to-read journals or found only in University libraries. Still, it would be ideal for breeders to have an adequate range of individuals to choose for a breeding program.
I do believe, in my Cassandra mode, that better rose species descriptions will emerge over the next few years, as biologists and botanists venture into the remote reaches of SE Asia. I will be interested to see the North-South range of these Asia species. Is there a geologist among us who can describe the effect of the glaciations on that part of the world? In North America (and probably Europe) we can follow the movement and, potentially, the speciation, of rose species with the extent of the ice caps during glaciations. We find really extreme forms of Rosa woodsii in southern New Mexico, for example. If I understand the articles correctly, the working hypothesis is that roses originated and radiated from SE Asia. That would usually mean that there should be a swarm of differentiated species in that immediate area, and less differentiation the further the species are found from that point. We may find that the most evergreen species are also the most restricted in geographical range. I would speculate that if we are looking for useful species to use in breeding, we should select from those species a little further away from the cradle that still retain the evergreen trait, in that they may have a wider geographic range to which they are adapted.
Wow,I learned allot from this thread! Robert , as an amateur rose breeder,I have to give credit to the A.R.S. and a Rose Show for initially sparking my interest in roses. I have noticed an increased interest within the A.R S. in those things you mentioned, such as responsible garden practices and an enlightened younger generation. I think that one of the most important functions of the A.R.S. is the excitement for roses created by a rose show. My own rose society has had rose “displays” instead of rose shows for the last two years due to decreased membership. We do allot of “educating” by volunteering at plant related events etc. I taught kids at my High School how to hybridize with seeds sent to me by Paul Bardon. A couple of years ago,the Rose Test Garden in Seattle’s Woodland Park Zoo was one half unsprayed, and only supplemented naturally. I am continually amazed at the generosity and friendships extended throughout the rose community. (Just my 2 cents) Robyn
Yes Robyn, there’s hope! Changes are being implemented.
Rose displays and sustainable cultivation methods are the future in my opinion.
You get all of the benefits of the benefits of the rose show without elitism and the emphasis on perfectionism which has led to reliance on hazardous chemical intervention and consequent unrealistic expectations for the general rose growing public. Education is the way to go.
It is up to an enlightened younger generation. I was one of the youngest members of our local rose society and that’s not saying much.
I did my bit for awhile but trying to do undo the rose show mentality is beyond my powers of persuasion. I no longer belong nor participate. I can afford to wait for a new mentality to supplant the old.
As for species. I totally agree with Don. Species seldom breed true unless isolated in nature. DNA analysis will tell the tale and the evidence is irrefutable.
Species are plastic and always evolving. I can’t be bothered splitting taxonomical hairs. We have to go with what we think we know and let someone else argue the details.
“Species are plastic and always evolving. I can’t be bothered splitting taxonomical hairs. We have to go with what we think we know and let someone else argue the details.” - Robert
As you do I hope that with renewed eastern asia rose exploration the background of old asian cvs will be better known and also that new and useful species or forms will be brought to use.
Of course if not very young and very adventurous minded our goal is not breeding plants with all species features.
As many many breeders did over centuries of roses breeding we would like to join the best features of modern roses with species strengths.
Along this line a constant fact is that the rare and outstanding achievements were poor parents at forwarding species strengths that allways dilute up to be lost. When tetraploidy is quite favorable to desirable features accumulation.
Building up consanguinity is a partial explanation.
There is another: if species or ancestral cvs positive features were monogenic or on a single chromosome preserve and cumulate them in successive generations should have been quite easy as it should be nowadays. It is very probable that many roses features are polygenic and polychromosomal controled. Be it through modifiers such as expressors/repressors does not contradict.
It is an obvious explanation to the fact that species strengths; desease resistance or scent were so readily lost in modern roses when preserved for millenaries in wild species.
That this fact is no more highlighted and has so little consequences is amazing is
Whence my conviction that it is very probable that many roses features are polygenic and polychromosomal controled…
As stated earlier, modern roses as well as allmost all roses vars are quite consanguine with many common ancestors appearing from the very beginnings everywhere in every var parentage tree. That is in its mother and father as well as in all four grandparents and so on but the rare and remote species outcross.
Not a problem if roses were inbreding plants but all genus rosa species are either self sterile or tolerate inbreding as a last resort if no other convenient pollen is available. This tolerance being higher with polyploid species and still more for the complex hybrid polyploids that are modern roses.
The word consanguinity I use deliberately as everybody knows that for oubreeding beings it is linked with many bad consequences.
However consanguinity is often a usefull breeders tool allowing building up of positive features. This breeding strategy name is line breeding. Typivaly with generations of sibcrosses. Something allmost absent among roses pedigrees. The very rare ones that could qualify are open pollinated that is foreign pollen allways a possibility.
Consanguinity is used in line breeding to cumulate positive features and specialy raise said positive features transmissibility as well as eliminate the unwanted ones. Aim being often to ultimately combine two different lines in order to overcome the allmost unavoidable consanguinity downpoints.
Do we find something like bettered positive features transmissibility?
On the contrary modern roses positive features transmissibility constantly dwindles.
Bad consequences of consanguinity that are debilitation and desease succeptibility more than outweigh its plus point that is a sophisticated flower…
No, not everyone knows the bad consequences of outbreeding. Or at least I don’t, Pierre. I do know that one consequence is completely unexpected and unpredictable offspring, a lack of consistency - - which is the reason for outbreeding. Outcrosses of Rosa species x (highly bred culivars) have produced some of the most luxuriant, healthy, spectacular roses grown, though invariably large and often once-blooming. I think of roses like Nevada, Schoener’s Nutkana, Alba Odorata, Mermaid, the Fr