Infrared as a pollination signal.

Understanding the relationships between long-dead organisms is tricky. Flowering plants (angiosperms, a group within the seed plants) are pollinated by a wide diversity of animals, which use scent and color as long-range and mid- to short-range signals, respectively. But the fossil rec ord indicates that other seed-plant lineages that arose earlier were also likely pollinated by insects, despite little evidence of color-based signaling. On page 1164 of this issue, Valencia-Montoya et al. (1) demonstrate that one of these earlier diverging seed-plant lineages, the cycads, use infrared radiation at dusk as a signal to attract beetle pollinators. In the beetle antennae, similar receptors to those used by predators, such as snakes, to detect prey allow the insects to find the cycads' thermogenic reproductive structures in the dark. This discovery explains ancient pollinator attraction and might also explain why some animal-pollinated groups diversified more than others. [ABSTRACT FROM AUTHOR]