Comissão Executiva do Plano da Lavoura Cacaueira, ERJOH, Marituba, Pará, Brazil.
Heredity (Edinb). 2011 Jun;106(6):973-85. doi: 10.1038/hdy.2010.145. Epub 2010 Dec 8.
Understanding the mating patterns of populations of tree species is a key component of ex situ genetic conservation. In this study, we analysed the genetic diversity, spatial genetic structure (SGS) and mating system at the hierarchical levels of fruits and individuals as well as pollen dispersal patterns in a continuous population of Theobroma cacao in Pará State, Brazil. A total of 156 individuals in a 0.56 ha plot were mapped and genotyped for nine microsatellite loci. For the mating system analyses, 50 seeds were collected from nine seed trees by sampling five fruits per tree (10 seeds per fruit). Among the 156 individuals, 127 had unique multilocus genotypes, and the remaining were clones. The population was spatially aggregated; it demonstrated a significant SGS up to 15 m that could be attributed primarily to the presence of clones. However, the short seed dispersal distance also contributed to this pattern. Population matings occurred mainly via outcrossing, but selfing was observed in some seed trees, which indicated the presence of individual variation for self-incompatibility. The matings were also correlated, especially within (Ρ(p(m))=0.607) rather than among the fruits (Ρ(p(m))=0.099), which suggested that a small number of pollen donors fertilised each fruit. The paternity analysis suggested a high proportion of pollen migration (61.3%), although within the plot, most of the pollen dispersal encompassed short distances (28 m). The determination of these novel parameters provides the fundamental information required to establish long-term ex situ conservation strategies for this important tropical species.
了解树种种群的交配模式是原地遗传保护的关键组成部分。在这项研究中，我们分析了巴西帕拉州一个可可连续种群中果实和个体的遗传多样性、空间遗传结构（SGS）和交配系统以及花粉扩散模式。在一个 0.56 公顷的样地中，共有 156 个个体被绘制并针对 9 个微卫星位点进行了基因型分析。为了进行交配系统分析，从 9 棵母树中采集了 50 颗种子，每棵树采集 5 个果实（每个果实采集 10 颗种子）。在 156 个个体中，有 127 个具有独特的多位点基因型，其余的是克隆。该种群在空间上是聚集的；它表现出显著的 SGS，可达 15 m，这主要归因于克隆的存在。然而，短的种子扩散距离也促成了这种模式。种群交配主要通过异交发生，但在一些母树上观察到自交，这表明存在个体自交不亲和性变异。交配也存在相关性，尤其是在个体内（Ρ(p(m))=0.607），而不是在果实之间（Ρ(p(m))=0.099），这表明少数花粉供体为每个果实授粉。亲权分析表明花粉迁移比例较高（61.3%），尽管在样地内，大部分花粉扩散都在短距离内（28 m）。这些新参数的确定为建立这个重要热带物种的长期原地保护策略提供了必要的基本信息。
