EPOW - Ecology Picture of the Week

Joshua Trees (Yucca brevifolia); Lily Family (Liliaceae)
Joshua Tree National Park, California

Explanation:  Behold the Joshua tree, the world's largest yucca, endemic to the Mojave Desert of southwest U.S.  Mormon pioneers named it for the Bible's Joshua with upraised arms, who led the Israelites from the desert into the promised land.  

This icon of the desert, however, owes its survival to a mere insect.  It relies entirely on the female yucca moth (Tegeticula) for pollination.  The moth has evolved an anatomy to facilitate spreading pollen across flowers of this plant, and a behavior to lay eggs in the ovaries of the flower.  Larvae of the moth then hatch and consume a portion of the flower's 30-50 seeds on which the moth depends.  The uneaten seeds germinate, thus beginning a new life cycle for the tree.  So tree and moth exist in a co-dependent relation of coevolutionary symbiosis.   

Joshua trees have persisted through lightening strikes and fires.  

According to one source, the Cahuilla tribe of Native Americans roasted and ate the seeds and flower buds, and used the fibers of the leaves in weavings of baskets and sandals.