|Dandelions and Lake Michigan|
|Dandelions decorating a lawn.|
The main advantage to asexual reproduction is the ability to capitalize on a successful genotype. If humans could do this, we might have hundreds of little Steve Jobs growing up to make our future world a better place. Instead, he left us a few offspring, but they each only have half his genes - and they may or may not have gotten the good ones. For dandelions, their successful growth strategy can be reproduced in perpetuity because they are identical copies, with only random mutations providing genetic diversity. Dandelions may have less need for genetic diversity, since the DNA they have allows them to grow differently depending on their growth conditions. This is what makes them such successful and widespread weeds.
One last issue for today: dandelions grow without being pollinated, but most dandelions do produce pollen (Did your childhood friends used to rub dandelions on your face? Remember the yellow dust they left behind?). Botanists scratch their heads a bit on this issue. Dandelions that don't produce pollen can make more seeds, since they are not wasting their energy. It may just be that because pollen production is genetically determined and dandelions don't evolve very quickly, the pollen production may just be an evolutionary leftover. Also, there are some sexually-reproducing dandelions in the world, so if dandelions maintain the ability to pollinate potential dandelion mates, they could just happen upon a better combination of genes than the ones they already have. I don't know that dandelions really need to become more successful at growing...though I love them, we have enough already!