Tropical breeding systems: one and done?

Abstract

Gene movement between individuals within populations and gene flow between populations can have major impacts on the distribution of genetic variation across landscapes. Gene flow introduces novel genetic variation into populations and reduces genetic differentiation among populations. However, during the first few decades following the Neo-Darwinian synthesis, gene flow proved to be difficult to measure accurately. It was not until molecular genetic markers became available that parentage analyses made possible accurate descriptions of contemporary gene movement patterns (for example, Ellstrand and Marshall, 1985). Over the past 30 years many plant species have been the subject of parentage analyses, including a number of tropical tree species. The lower densities that characterize most of the tropical trees allow more accurate estimates of gene movement patterns owing to less pollen parent ambiguity. Studies measuring the levels and distances of gene flow within fragmented tropical landscapes have been particularly popular. Generally, reported gene flow rates are high (>50%), and insect-vectored pollen is often transported up to several kilometers (Hamrick, 2010).