Conspecific Male Plant Competition
Most biologists agree that males fighting in competition for females has no scope in plants. ~ Argentinian botanist Andrea Cocucci et al
Male mating competition is not confined to animals. Several conspecific plants compete to mate, as pollen battle their way to an awaiting ovule. Via chemical conflict, wild radish pollen grains duke it out for the privilege of pollination.
Milkweed reproduce by hooking sacs of pollen grains – pollinaria – to the bodies of birds and other pollinators. Pollinaria are unwittingly dropped into another flower to complete pollination.
It is possible for multiple pollinaria to entangle due to the limited number of attachment points on the pollinator. The adaptive solution was horns that prevent pollen sacs from hooking together. Horns favor the flower that a pollinator visits first. Just as beetle and ungulate stag horns are the implements of male competition, pollarium horns force flower competition to the fore.
Neither self-propulsion nor well-developed sensory perception are required for sexual selection to take place through intrasexual struggles. Apparently, only physical contact is enough to influence the reproductive success of competitors and to promote the evolution of defensive and attack weaponry. ~ Andrea Cocucci et al