(Iriartea deltoidea) taking over an abandoned Costa Rican pasture exhibit much less genetic diversity than those in a neighboring old-growth forest, scientists say. Writing in the current Science, they report that two of the 66 old-growth forest trees whose DNA they studied contributed more than half of the genes to the second-growth forest pioneers; 41 passed along nothing at all. In many tropical countries, second-growth forests cover more area than do old-growth forests.