I can remember when I was young that we used to make dandelion chains by looping long stemmed dandelions together. My neighbors were talking about that the other day when I suddenly realized that I rarely see a long stemmed dandelion anymore. My friends I agreed that indeed, long stemmed dandelions seem to have disappeared. Last few days I've been looking around and I have spotted a few but not many. My interest piqued, I tried googling the subject of dandelion evolution and I found out that some people have had the same observation. One article claims that its Darwinism at work. When I mow the grass, shorter dandelions are spared the blade and because of this, short stemmed dandelions are allowed to proliferate, their seeds spread all over the countryside. Whereas any long stemmed varieties are cut down before they can go to seed. As a result the dandelion has adapted to avoid the mower so to speak. If your lawn is like mine with a few weeds here and there then you should notice some short stemmed dandelions survive the cut. Check it out, its really quite noticeable around here, long stemmed dandelions are all of a sudden hard to find. Is this really evolution at work, even mildly? If so will long stemmed dandelions eventually disappear? Or is this just a suburban phenomena?
perhaps at were you are long dandelions will dissapear...but in many other places were such selection is not at hand...evolution will pass its own route. In Russia for example the dandelions are sooo long that their length is larger than circumference of my head many times over. Please Register or Log in to view the hidden image! also perhaps the long dandelions are dissapearing because there is more sun in the area...so that the stems dont need to be so long anymore...those dandelions that rise above the grass do not pass their seeds because they dry up in the sun...while shorter ones do pass the seeds. Perhaps such is the mechanism.
I didn't think it worldwide but I find it interesting to perhaps be viewing natural selection if only in a micro-setting. Out of curiousity, do long stem outnumber short stem in Russia?
Some of the reasons the stems of dandelions might have gotten shorter: 1) chemical toxins in soil decrease ability to absorb nutrients (malnourishment) (http://aob.oxfordjournals.org/cgi/c...on&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT) 2) nutrients malnourishments (direct) decrease different phenotype expression thus limiting the gene for long stem...perhaps the long stem is a recessive allele (http://aob.oxfordjournals.org/cgi/c...on&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT)
I would say they do...but my conclusive answer would be: depends on the area the dandelion is found. Usually in the city...the dandelions I see have short stems. While in the forest they are extremely long...and found amongst the grass.
I see the long stems more in the countryside but not as many as I used to. Lawn mowers have given the short stem dandelion a chance to proliferate by eliminating the competition. Right now in suburban America a short stem dandelion's seeds have a better chance of survival and are more apt to dominate the landscape because their counterpart is finding it difficult to adapt.
This year we have a dandelion riot! I actually have a picture of at least 20 flowers coming out of 1 root! The field where we run the dogs is literally covered with dandelions. I don't remember a year when they were so everywhere... The best way to remove is to do it mechanically, by hand and using a small digger...
There are different kinds of dandelions. A lot of the ones in the US are clones - they don't do sexual recombination, so their adaptation would be slower. But possible. Short dandelions, quick-maturing elms, squirrels that don't double back when fleeing, we are a selection environment for so many beings - - -
Personal observation, from a lot of driving rural and urban. I actually kept track for a while, on paper. I have no life. Take it for what it's worth.
