Meeting Abstract
Natal homing is a pattern of behavior during which animals leave their geographic area of origin before returning to reproduce in the same location where they began life. Despite evidence that natal homing is widespread, little is known about how it is accomplished. A recent idea, known as geomagnetic imprinting, notes that unique magnetic fields mark different geographic areas. Thus, animals that detect Earth’s magnetic field, such as sea turtles, might learn the field that exists in their natal area when they are young and use this information to return as adults. While natal homing is well established in sea turtles, some populations show a perplexing genetic structure where adjacent nesting beaches are genetically distinct, but geographically isolated nesting beaches are genetically similar. These patterns could arise through magnetic navigation to natal beaches when distant beaches have similar magnetic fields and neighboring beaches have different fields. In these instances, a turtle searching for its natal beach might find a location with an appropriate magnetic field that is actually far from its target. Thus, the geomagnetic imprinting hypothesis predicts that, regardless of geographic distance, nesting beaches with similar magnetic fields should be genetically similar, and nesting beaches with different fields should be genetically distinct. Analyses of published data confirmed this prediction; we found that spatial variation in Earth’s field is a strong predictor of genetic differentiation, while geographic distance is not. The results corroborate initial reports that geomagnetic imprinting underlies natal homing and suggest that sea turtle genetic structure is, at least in part, mediated by magnetic navigation to nesting sites.
