Polo Reg Desenvolvimento Tecnol Ctr Sul, APTA, BR-13400970 Piracicaba - Brazil
Total Affiliations: 3
FOREST ECOLOGY AND MANAGEMENT;
MAY 15 2015.
Web of Science Citations:
Pioneer tree species exhibit life-cycle characteristics and population structures that are mainly affected by natural or human disturbances. In primary forests, demographic dynamics of pioneer species may resemble those defined for a metapopulation. In early successional forests, the patterns of establishment, survival and reproduction are mainly determined by microclimate and biota modifications of the site after the human disturbance. The aim of this study was to investigate how the ecological processes and the population genetic factors associated with disturbances can affect the genetic diversity and structure of populations of a pioneer tree species: Croton floribundus Spreng. (Euphorbiaceae). Nuclear and chloroplast microsatellite markers were examined in plants of two size classes sampled in four gaps of primary forest and four sub-areas of early successional forest. Despite presenting similar genetic diversity levels, the genetic diversity was distributed differently between forests. The combined effects of seed dispersal and colonizations (and extinctions) were determinants of the fine-scale genetic structure of C. floribundus. The main finding was that human disturbances seem to boost the influence of founder effects in populations of a species with limited seed dispersal. Results suggested that gene flow by pollen was responsible for maintaining the genetic diversity within populations of C. floribundus in both forests, but in the early successional forest, gene flow by seeds was equally important. We conclude that gap dynamics, colonization, and pollen and seed dispersal affect the genetic diversity and structure of the pioneer species depending mainly on the number of colonizers, the number of source populations, the gene flow rates, and the level of human disturbance. (C) 2015 Elsevier B.V. All rights reserved. (AU)