Population density and size influence pollen dispersal pattern and mating system of the predominantly outcrossed Banksia nivea (Proteaceae) in a threatened ecological community

Gene flow is a critical component of plant mating systems and influences population fitness, yet pollen dispersal can be highly variable and influenced by natural and anthropogenic fragmentation. Gene flow through pollen dispersal was investigated in two populations of contrasting size and habitat context in Banksia nivea ssp. uliginosa, a rare species in the Busselton ironstone threatened ecological community with a naturally fragmented distribution. Paternity analysis was conducted with seven microsatellite loci to determine mating system parameters and patterns of pollen dispersal. Outcrossing was high in both populations with a similar level of selfing for both populations despite differences in population size, density and vegetation matrix. Most mating occurred within 10 m of a mother plant in the small, clumped population, while more dispersed mating, up to 50 m from a mother plant, was recorded in the large, less dense population. Our results show that population density and siz...

基因流（Gene flow）是植物交配系统的核心组成部分，对种群适合度具有关键影响；然而花粉扩散（pollen dispersal）往往呈现高度变异性，且易受自然与人为片段化作用的调控。本研究以分布于巴瑟尔顿铁矿床受威胁生态群落中的珍稀物种班克木沼生亚种（Banksia nivea ssp. uliginosa）为研究对象，该物种自然分布本就呈片段化格局。研究选取该物种的两个种群展开实验，二者在种群规模与生境背景上均存在显著差异。研究采用7个微卫星位点（microsatellite loci）开展父本分析（paternity analysis），以明确其交配系统参数与花粉扩散模式。结果表明，尽管两个种群在种群规模、种群密度及植被基质方面均存在差异，但二者的异交（outcrossing）水平均较高，且自交（selfing）水平相近。在小型集群种群中，多数交配事件发生在母株10米范围内；而在大型低密度种群中，交配事件的扩散范围更广，最远可达母株50米外。本研究结果显示，种群密度与规