Plant-fungal coevolution and speciation on a remote oceanic island

自从达尔文的开创性工作以来，我们对物种起源（物种形成）的理解发生了很大的变化。然而，被忽视的一个方面是微生物在推动物种形成中的作用。在这里，我们提出了一个新的机制，物种的起源，即共同进化的分歧，在植物菌根协会增加当地的适应，并导致完成物种形成。虽然众所周知，物种可能会因地理障碍而分化，如山脉或海洋，但种群也可能在基因流动的情况下分裂，而不会出现地理隔离，例如通过专门化栖息地或资源。在这种情况下，共生协会，植物与微生物可能是特别强大的，同时促进当地的适应和生殖隔离，导致speciation.We将集中对豪勋爵岛，一个偏远的岛屿在塔斯曼海，和他们的相互作用与丛枝菌根真菌特有的植物的姐妹种。使用豪勋爵岛植物群的系统发育、细胞核学和生态学数据，监督员Savolainen先前证明，事实上，在某些情况下，基因流的物种形成可能是频繁的，并且可以解释五分之一的LHI特有植物物种（PNAS 108，13188-93，2011）。这些例子，如Coprosma和Metrosideros，将被研究这个博士学位。我们假设土壤和土壤微生物影响了祖先种群的局部适应，这反过来又导致了开花时间的差异，并最终促进了物种形成。不同水平的菌根定殖和基因表达的植物宿主和菌根协会共同调节可能导致出现不同的人口占据不同的环境（土壤，海拔梯度等）。我们将使用宏基因组学和RNA-seq结合田间/温室实验来测试关键假设。这项工作有可能带来对物种形成机制以及共同进化如何促进物种分化的深刻反思。这项拟议中的工作将解开进化中一些最被忽视的假设，例如微生物如何驱动植物物种形成，以及微生物组与植物多样性之间的联系。鉴于植物-菌根共生的广泛性，它们在作物生产中的重要性，以及土壤和植物多样性在生态系统功能中的突出地位，我们的研究也将在应用生态学和农业中产生深远的影响，超越进化生物学。

Our understanding of how species originate (speciation) has changed considerably since Darwin's seminal work. One aspect, however, that has been ignored is the role that microbes can play in driving speciation. Here, we propose a new mechanism for the origin of species, whereby coevolutionary divergence in plant-mycorrhizal associations increases local adaptation and leads to the completion of speciation. While it is well known that species can diverge due to geographic barriers such as mountain ridges or oceans, populations can also split in the face of gene flow without geographic isolation, for example through specialisation to habitats or resources. In this context, symbiotic associations that plants have with microbes may be particularly powerful in simultaneously facilitating local adaptation and reproductive isolation leading to speciation.We will focus on pairs of sister species of plants endemic to Lord Howe Island, a remote island in the Tasman sea, and their interactions with arbuscular mycorrhizal fungi. Using phylogenetic, karyological, and ecological data for the flora of Lord Howe Island, Supervisor Savolainen previously demonstrated that speciation with gene flow may, in fact, be frequent in some instances and could account for one in five of the endemic plant species of LHI (PNAS108, 13188-93, 2011). These examples, such as Coprosma and Metrosideros, will be studied for this PhD. We hypothesise that soil and soil microbes have affected local adaptation of the ancestral populations, which in turn led to differences in flowering time, and ultimately promoted speciation. Differing levels of mycorrhizal colonisation and gene expression coregulated in plant host and mycorrhizal associations may have led to the emergence of distinct populations occupying different environments (soil, altitudinal gradient, etc). We will test key hypotheses using metagenomics and RNA-seq combined with field/greenhouse experiments. The proposed work has the potential to bring drastic rethinking about the mechanisms of speciation and how coevolution contributes to species divergence. The proposed work will unravel some of the most neglected hypotheses in evolution, such as how microbes can drive plant speciation, and hence the link between microbiome and plant diversity. Given the widespread nature of plant-mycorrhizal symbioses, their importance in crop production, and the prominence of soil and plant diversity in ecosystem functioning, our research will also havefar-reaching impact in applied ecology and agriculture, beyond evolutionary biology.