Did the Sunda-Sahul Biotic Exchange result in plant diversification? A case study of switching disperser communities and fruit traits in Aglaia (Meliaceae)

舜达大陆架(包括马来西亚半岛、文莱和印度尼西亚部分地区)和萨胡尔大陆架(包括澳大利亚和新几内亚)首次相撞25Mya。这种碰撞第一次促进了在每个大陆架上孤立进化的生物群的交换。这一“Sunda-Sahul生物交换”对该地区的生物多样性产生了重大影响，但剩下的一个关键问题是，这种交换是否推动了生物群的多样化。跳过大陆架的谱系暴露在新的选择压力下，我们假设这导致了特征的差异。为了验证这一假设，我们正在寻求资金，进行一项关于Sunda-Sahul生物交换对木兰属(Meliaceae)果实性状的影响的案例研究。Aglaia是约127种热带树种的一个属，分布在Sunda和Sahul货架上，具有显著的水果多样性。据报道，物种被灵长类动物、会飞的鸟类或不会飞的毒蛇驱散。鉴于Sunda和Sahul架子上的分散者群落的明显差异--特别是Sahul上没有灵长类动物--我们的目标是测试不同的分散者群落是否推动了Aglaia在Sunda和Sahul架子上迁徙时水果性状的多样性。为此，我们打算在三年内实现三个主要目标。首先，我们将使用定制的诱饵试剂盒对目标基因座进行下一代测序，从而生成一个健壮的、物种完整的Aglaia和相关属的系统发育图。其次，我们将通过对标本馆和野外采集的标本进行发育、解剖和化学分析，对仙人掌果实进行深入的特征描述。然后，将在系统发育框架内重建Aglaia的水果性状进化。第三，我们将实施尖端分析，以测试水果形态的变化是否由分散者群落的差异驱动。这将首先通过重建Aglaia的生物地理历史并使用系统发育比较模型来测试生物地理跳跃是否与水果性状切换相关。随后，我们将在新的生态进化模拟引擎Gen3sis中建立一个空间上显式的机制模型，以明确测试新生物地理区域的分散者群落的差异是否导致水果性状多样化，并排除其由其他非生物因素(如气候)或中性过程(如遗传漂移)造成的可能性。最终，该项目将为Sunda-Sahul生物交易所和世界各地其他类似的生物交流活动提供新的见解，并揭示导致一个巨大多样性热点的多样性演变的过程。

The Sunda continental shelf (including Peninsular Malaysia, Brunei and parts of Indonesia) and Sahul continental shelf (including Australia and New Guinea) collided for the first time 25 Mya. This collision for the first time facilitated the exchange of biotas that had evolved in isolation on each shelf. This “Sunda-Sahul Biotic Exchange” had a significant effect on the biodiversity of the region, but a key question remaining is whether the exchange drove the diversification of biota. Lineages that jumped continental shelves were exposed to novel selection pressures, and we hypothesise that this led to the divergence of traits. To test this hypothesis, we are seeking funding to conduct a case study on the effect of the Sunda-Sahul Biotic Exchange on fruit traits in Aglaia (Meliaceae). Aglaia is a genus of c. 127 tropical tree species distributed across the Sunda and Sahul shelves, with remarkable diversity in fruits. Species have been reported to be dispersed either by primates, flying birds, or the flightless cassowary. Given the stark differences in disperser communities across the islands of the Sunda and Sahul shelves – and particularly the absence of primates on Sahul – we aim to test whether the different disperser communities drove the diversity of fruit traits in Aglaia as it migrated across the Sunda and Sahul shelves. To do this, we intend to achieve three main objectives over three years. Firstly, we will generate a robust, species-complete phylogeny of Aglaia and related genera using next-generation sequencing of targeted loci using a custom bait-kit. Secondly, we will conduct an in-depth characterisation of Aglaia fruits through developmental, anatomical and chemical analyses conducted on herbarium and field-collected specimens. Fruit trait evolution in Aglaia will then be reconstructed in a phylogenetic framework. Thirdly, we will implement cutting-edge analyses to test whether switches in fruit morphology were driven by differences in disperser communities. This will be done initially by reconstructing the biogeographic history of Aglaia and using phylogenetic comparative models to test whether biogeographic jumps are correlated with fruit trait switches. Subsequent to this, we will build a spatially explicit mechanistic model in the new eco-evolutionary simulation engine gen3sis, to explicitly test whether the differences in disperser communities in new biogeographic areas are causing fruit trait diversification, and exclude the possibility that it is due to other abiotic factors such as climate, or neutral processes such as genetic drift. Ultimately, this project will give new insight into the Sunda-Sahul Biotic Exchange and other similar biotic exchange events worldwide, and shed light on the processes leading to the evolution of diversity in a megadiverse hotspot.