Although scientists have known since the middle of the 19th
century that the tropics are teeming with species while the poles harbor
relatively few, the origin of the most dramatic and pervasive biodiversity on
Earth has never been clear.
New research sheds light on how that pattern came about.
Furthermore, it confirms that the tropics have been and continue to be the
Earth’s engine of biodiversity.
By examining marine bivalves (two-shelled mollusks,
including scallops, cockles and oysters), a model system for large-scale
ecological and evolutionary analysis, the study shows that most evolutionary
lineages started in the tropics and expanded outward.