Nge Francis J, Hammer Timothy A, Vasconcelos Thais, Biffin Ed, Kellermann Jürgen, Waycott Michelle
School of Biological Sciences, Faculty of Science, The University of Adelaide, Adelaide, SA 5000, Australia.
National Herbarium of New South Wales, Botanic Gardens of Sydney, Mount Annan, NSW 2567, Australia.
Ann Bot. 2025 Feb 19;135(3):531-548. doi: 10.1093/aob/mcae181.
Polyploidy is an important evolutionary driver for plants and has been linked with higher species richness and increases in diversification rate. These correlations between ploidy and plant radiations could be the result of polyploid lineages exploiting broader niche space and novel niches due to their enhanced adaptability. The evolution of ploidy and its link to plant diversification across the Australian continent is not well understood. Here, we focus on the ploidy evolution of the Australasian Rhamnaceae tribe Pomaderreae.
We generated a densely sampled phylogeny (90 %, 215/240 species) of the tribe and used it to test for the evolution of ploidy. We obtained 30 orthologous nuclear loci per sample and dated the phylogeny using treePL. Ploidy estimates for each sequenced species were obtained using nQuire, based on phased sequence data. We used MiSSE to obtain tip diversification rates and tested for significant relationships between diversification rates and ploidy. We also assessed for relationships between ploidy level and niche breadth, using distributional records, species distributional modelling and WorldClim data.
Polyploidy is extensive across the tribe, with almost half (45 %) of species and the majority of genera exhibiting this trait. We found a significant positive relationship between polyploidy and genus size (i.e. species richness), but a non-significant positive relationship between polyploidy and diversification rates. Polyploidy did not result in significantly wider niche space occupancy for Pomaderreae; however, polyploidy did allow transitions into novel wetter niches. Spatially, eastern Australia is the diversification hotspot for Pomaderreae in contrast to the species hotspot of south-west Western Australia.
The relationship between polyploidy and diversification is complex. Ancient polyploidization events likely played an important role in the diversification of species-rich genera. A lag time effect may explain the uncoupling of tip diversification rates and polyploidy of extant lineages. Further studies on other groups are required to validate these hypotheses.
多倍体是植物重要的进化驱动力，与更高的物种丰富度和多样化速率的增加有关。多倍体与植物辐射之间的这些关联可能是由于多倍体系利用了更广泛的生态位空间和新生态位，因其适应性增强。在整个澳大利亚大陆，多倍体的进化及其与植物多样化的联系尚未得到很好的理解。在这里，我们聚焦于澳大拉西亚鼠李科Pomaderreae族的多倍体进化。
我们构建了该族的一个密集采样系统发育树（90%，215/240种），并用于检验多倍体的进化。我们为每个样本获取30个直系同源核基因座，并使用treePL对系统发育树进行定年。基于分阶段的序列数据，使用nQuire获得每个测序物种的多倍体估计值。我们使用MiSSE获得末端多样化速率，并检验多样化速率与多倍体之间的显著关系。我们还利用分布记录、物种分布建模和WorldClim数据评估多倍体水平与生态位宽度之间的关系。
多倍体在整个族中广泛存在，几乎一半（45%）的物种和大多数属表现出这一特征。我们发现多倍体与属的大小（即物种丰富度）之间存在显著的正相关，但多倍体与多样化速率之间存在不显著的正相关。多倍体并没有导致Pomaderreae族占据显著更广泛的生态位空间；然而，多倍体确实允许向新的更湿润的生态位转变。在空间上，与澳大利亚西南部的物种热点相反，澳大利亚东部是Pomaderreae族的多样化热点。
多倍体与多样化之间的关系是复杂的。古老的多倍体化事件可能在物种丰富的属的多样化中发挥了重要作用。滞后时间效应可能解释了现存谱系的末端多样化速率与多倍体的解耦。需要对其他类群进行进一步研究以验证这些假设。
