A few weeks ago I came across some wild garlic (Allium vineale, Liliaceae) at Side Cut Metropark near Maumee, Ohio. In late June each tall, hollow stalk bore a swollen bulb-like object near the top. A couple of weeks later, the papery husks were splitting open to reveal bulbils and flowers:
Wild garlic can reproduce sexually with flowers and seeds, or asexually with aerial bulbils or offshoots from the underground bulbs (Ronsheim and Bever 2000). The reproduction methods aren’t mutually exclusive, and the plants can utilize multiple methods at the same time. To what extent each of the three reproduction methods are utilized depends largely on genetics and selection pressures in a given location (Ronsheim and Bever 2000). Asexual reproduction with no genetic variation may be more favored in areas of stable, healthy growth. Related asexual plants are identical and have the same fitness. Their abilities to grow and reproduce are the same. When things are good, there’s no reason to “rock the boat,” so to speak.
In the presence of pathogens and other negative selection pressures, however, plants exhibiting sexual reproduction may be favored. Sexual reproduction results in more diverse genes that convey new traits to the plants. Some of these genetically diverse plants may be more capable of surviving and reproducing in the presence of a given threat.
The plants shown here seemed to be hedging their bets by growing both bulbils and flowers (and perhaps underground bulb offshoots). Some of their offspring will be identical, and some will have genetic variation. The ability for wild garlic to “roll with the punches” by changing its reproductive strategy allows it to thrive in both good and bad times. This plant was introduced to North America from Europe, and has since had no trouble spreading across much of the continent. It’s so successful, in fact, that several states list it as a noxious weed.
Ronsheim, M.L. and J.D. Bever. 2000. Genetic variation and evolutionary trade-offs for sexual and asexual reproductive modes in Allium vineale (Liliaceae). American Journal of Botany 87(12):1769-1777.