The role of patch processes in regulating regional dynamics in annual plant metapopulations

一年生植物占据了广泛的自然、半自然和人为干扰的栖息地。因此，它们可能构成一个地区生物多样性的重要组成部分。由于它们的一代时间短，一年生植物也可能对新的选择压力做出快速反应，但这取决于它们种群中保持了多少遗传多样性，以及这种多样性是如何构建的。了解一年生植物种群的精细结构可能看起来微不足道，但实际上对于理解调节一年生植物种群遗传多样性的因素以及它们对自然选择的反应能力至关重要。这对于杂草种群的管理、路边生物多样性的测量和管理以及预测一年生植物对环境变化的反应具有潜在的重要意义。以前的工作集中在两个不同层次的空间组织和过程。一方面，研究已经解决了密度如何影响交配系统和种群内基因流动模式，以及这些如何反过来影响种群遗传结构。另一方面，研究已经解决了种群间基因流动的重要性和潜在的元种群动态（即灭绝和再殖民化）在一个破碎的景观中对种群内部和种群之间遗传多样性的影响。由于离散的斑块级殖民化，可能建立连续种群的可能性几乎没有得到解决。在该模型下，种群的局部扩张不是通过依赖于密度的扩散，而是通过在小空间尺度上建立斑块（由于非常局部的分散），然后通过扩散的斑块扩张来关闭斑块之间的间隙。其结果是一个空间扩展的种群，其遗传结构将与其物理形状大不相同。该项目将验证种群内斑块动态在种群内遗传多样性的限制和结构中起关键作用的假设。换句话说，我们假设种群内几米尺度上的殖民化和灭绝动态在遗传多样性模式中起着重要作用。种群和斑块的定义显然很重要；在这里，通常，种群是分布在空间上的个体或多或少连续的阵列；斑块是个体的空间阵列，这些个体与其它这样的阵列相隔至少单个植物的空间范围的一个数量级的距离。因此，对于直径为30厘米的一年生植物，斑块定殖将取决于几米范围内的扩散。我们将通过使用斑块内多样性和斑块间分化来验证我们的假设，这些斑块分布在一年生植物金银花的种群范围内。由于斑块定殖对遗传多样性模式的影响将被随后在斑块之间的基因流动所侵蚀，我们将比较是否含有雄性斑块的不同斑块的多样性和分化；有雄性的斑块比没有雄性的斑块交换基因的速度更快。我们还将利用我们的研究来展示我们开发的一种新技术，以一种允许标准二倍体群体遗传学的方式对多倍体植物进行基因分型。这种方法包括从多倍体基因组的一个组成基因组中扩增微卫星。在M. annua的情况下，我们将使用微卫星进行群体遗传分析，只在姐妹物种M. huetii贡献的基因组中扩增。

Annual plants occupy a broad range of natural, semi-natural and human-disturbed habitats. They thus may constitute an important component of a region's biodiversity. Because of their short generation times, annual plants may also respond quickly to new selective pressures, but this depends on how much genetic diversity is maintained in their populations, and how this is structured. A knowledge of the fine-scale structure of annual plant populations might seem trivial, but it is in fact essential for understanding the factors that regulate the genetic diversity of annual plant populations and thus their ability to respond to natural selection. It is this potentially important for the management of weed populations, the measurement and management of road-side biodiversity, and for predicting responses of annual plants to environmental change. Previous work has focussed on two contrasting levels of spatial organisation and processes. On the one hand, studies have addressed how density affects the mating system and patterns of gene flow within populations, and how these in turn affect population genetic structure. On the other hand, studies have addressed the importance of gene flow amongst populations and potential metapopulation dynamics (i.e., extinctions and re-colonisations) in a fragmented landscape for the genetic diversity both within and between populations. The likely possibility that continuous populations might be established as a result of discrete patch-level colonisation has hardly been addressed. Under this model, populations expand locally not by density-dependent diffusion but rather by the establishment of patches over small spatial scales (due to very local dispersal), followed by the closure of gaps between patches through patch expansion by diffusion. The result is a spatially extended population whose genetic structure will be very different from its physical shape. This project will test the hypothesis that within-population patch dynamics play a key role in limiting and structuring within-population genetic diversity. In other words, we hypothesise that colonisation and extinction dynamics at scales of a few metres within a population play an important role in patterning genetic diversity. The definition of population and patch is evidently important; here, as is common, a population is a more or less continuous array of individuals distributed over space; a patch is an spatial array of individuals separated from other such arrays by a distance at least an order of magnitude of the spatial extent of an individual plant. Thus, for annual plants with a diameter of 30 cm, patch-colonisation will depend on dispersal over several metres. We will test our hypothesis by using within-patch diversity and between-patch differentiation for patches within a range of populations of the annual plant Mercurialis annua. Because the impact of patch colonisations on patterns of genetic diversity will be eroded by subsequent gene flow amongst patches, we will compare diversity and differentiation for patches that differ in whether they contain males; patches with males are expected to exchange genes at a greater rate than those without males. We will also use our study to showcase a novel technique that we have developed to genotype polyploid plants in a way that allows standard diploid population genetics. This approach involves the amplification of microsatellites from just one of the constituent genomes of the polyploid genome. In the case of M. annua, we will use microsatellites for our population genetic assays that amplify in only the genome contributed by the sister species M. huetii.