Optimal outcrossing in Ipomopsis aggregata: seed set and offspring fitness

Abstract

Restricted gene flow and localized selection should establish a correlation between physical proximity and genetic similarity in many plant populations. Given this situation, fitness may decline in crosses between nearby plants (inbreeding depression), and in crosses between more widely separated plants ("outbreeding depression') mostly as a result of disruption of local adaptation. It follows that seed set and offspring fitness may be greatest in crosses over an intermediate "optimal outcrossing distance'. This prediction was supported for Ipomopsis aggregata, a long-lived herbaceous plant pollinated by hummingbirds. -from Authors