Clues on how flowering plants spread
Scientists have long scratched their heads over the Earth’s dazzling array of flowering plants. While conifers took 300 million years to yield hundreds of species, flowering plants diversified in less than half that time into 250,000 species, encompassing everything from massive trees to the most delicate wildflowers, from hardy, low-growing alpine plants to bug-eating carnivores. Scientists have settled on a handful of likely factors that might have driven this blizzard of diversification, including competition between males to fertilize the egg cell hidden at the base of every flower. This male competition is familiar to anyone who has seen rams butt heads or stags lock antlers. It is a decidedly quieter process among plants, although the stakes are just as high. The competition occurs between pollen grains deposited on a flower. Each pollen grain holds three cells, two being the plant’s sperm cells and the third a tube-growing cell that rapidly creates a pathway...