Data from: Can facilitation influence the spatial genetics of the beneficiary plant population?

Plant facilitation is a positive interaction where a nurse or nurse plant community alters the local conditions, improving the life-time fitness of other beneficiary plants. In stressful environments, a common consequence is the formation of discrete vegetation patches under nurse plants, surrounded by open space. The consequences of such spatial patterns have been studied mostly at the community level. At the population level, facilitation causes a distribution of beneficiary individuals that could have intra-specific genetic consequences. The spatial patchiness and the increase in local aggregation can potentially affect the population fine-scale genetic structure. In addition, marked microenvironmental differences under nurses versus outside could lead to plastic phenotypic variation between facilitated and non-facilitated individuals, as for example reproductive asynchrony, potentially producing assortative mating. This study tests the hypothesis that plant facilitation can have genetic consequences for the population of a beneficiary plant (Euphorbia nicaeensis) by affecting its spatial genetic structure and mating patterns between subpopulations of facilitated and non-facilitated individuals. Facilitation in this system creates an aggregated distribution of beneficiary individuals compared to a minority of non-facilitated individuals that grow on the open ground. Facilitation also leads to slight phenological differences mediated by strong microenvironmental differences created by nurses compared to the open ground. Yet a molecular analysis showed that, although there is fine scale spatial genetic structure in this system, there is no evidence that it is caused by facilitation. Numerical simulations further showed that spatial genetic patterns in the population are little influenced by the phenological mismatch observed in the field. Synthesis. Facilitation leads to the strong spatial aggregation of beneficiary plants and desynchronizes their flowering phenology, but the magnitude of these effects is not enough to have local genetic consequences in our study system. Facilitation seems thus to have a homogenizing role by allowing the persistence of a diverse gene pool in populations in harsh environments, rather than fomenting genetic differentiation. Further information on other systems where facilitation produces stronger spatial or phenological effects on facilitated plants is needed to fill the large knowledge gap we have on the genetic effects of facilitation.植物促进作用（Plant facilitation）是一种正相互作用，指护伴植物（nurse plant）或护伴植物群落通过改变局域环境条件，提升其他受益植物（beneficiary plant）的终生适合度。在胁迫环境中，该作用的常见结果是在护伴植物下方形成离散植被斑块，斑块外围为开阔空地。此类空间格局的生态效应此前多在群落水平开展研究。在种群水平上，植物促进作用会使受益植物个体呈现特定分布格局，进而可能引发种内遗传效应。空间斑块性与局域聚集度的提升，可潜在影响种群的精细尺度遗传结构（fine-scale genetic structure）。此外，护伴植物下方与开阔空地间存在显著微环境差异，可能导致受护伴与未受护伴个体间产生表型可塑性变异（plastic phenotypic variation）——例如生殖异步性（reproductive asynchrony），进而可能引发选型交配（assortative mating）。 本研究针对“植物促进作用可通过影响受益植物（Euphorbia nicaeensis，倪凯大戟）的空间遗传结构，以及受护伴与未受护伴亚种群间的交配模式，对其种群产生遗传效应”这一假说开展验证。本研究的植物体系中，相较于生长在开阔空地的少数未受护伴个体，植物促进作用使受益植物个体呈现聚集分布格局。此外，相较于开阔空地，护伴植物营造的强烈微环境差异还会介导产生细微的物候差异。然而分子分析（molecular analysis）结果显示，尽管本研究体系中存在精细尺度空间遗传结构，但并无证据表明该结构由植物促进作用导致。数值模拟（numerical simulations）进一步表明，种群中的空间遗传格局几乎不受野外观测到的物候错配（phenological mismatch）影响。 综合分析结果显示，植物促进作用可促使受益植物形成强烈的空间聚集，并使其开花物候（flowering phenology）同步性降低，但上述效应的强度不足以在本研究体系中产生局域遗传效应。由此看来，植物促进作用在严酷环境中似乎发挥着均质化作用：它可维持种群内多样的基因库（gene pool），而非推动遗传分化（genetic differentiation）。未来仍需对其他能使受益植物产生更强空间或物候效应的植物促进体系开展研究，以填补当前在植物促进作用的遗传效应领域存在的大量知识空白。