Tribble Carrie M, Márquez-Corro José Ignacio, May Michael R, Hipp Andrew L, Escudero Marcial, Zenil-Ferguson Rosana
Department of Biology, University of Washington, Seattle, WA, 98195, USA.
Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, 98195, USA.
New Phytol. 2025 Mar;245(5):2350-2361. doi: 10.1111/nph.20353. Epub 2024 Dec 25.
The effects of single chromosome number change-dysploidy - mediating diversification remain poorly understood. Dysploidy modifies recombination rates, linkage, or reproductive isolation, especially for one-fifth of all eukaryote lineages with holocentric chromosomes. Dysploidy effects on diversification have not been estimated because modeling chromosome numbers linked to diversification with heterogeneity along phylogenies is quantitatively challenging. We propose a new state-dependent diversification model of chromosome evolution that links diversification rates to dysploidy rates considering heterogeneity and differentiates between anagenetic and cladogenetic changes. We apply this model to Carex (Cyperaceae), a cosmopolitan flowering plant clade with holocentric chromosomes. We recover two distinct modes of chromosomal evolution and speciation in Carex. In one diversification mode, dysploidy occurs frequently and drives faster diversification rates. In the other mode, dysploidy is rare, and diversification is driven by hidden, unmeasured factors. When we use a model that excludes hidden states, we mistakenly infer a strong, uniformly positive effect of dysploidy on diversification, showing that standard models may lead to confident but incorrect conclusions about diversification. This study demonstrates that dysploidy can have a significant role in speciation in a large plant clade despite the presence of other unmeasured factors that simultaneously affect diversification.
单条染色体数目变化——非整倍性介导的多样化效应仍未得到充分理解。非整倍性会改变重组率、连锁或生殖隔离，尤其是对于五分之一具有全着丝粒染色体的真核生物谱系而言。由于对沿着系统发育具有异质性的与多样化相关的染色体数目进行建模在定量方面具有挑战性，因此尚未估计非整倍性对多样化的影响。我们提出了一种新的染色体进化状态依赖多样化模型，该模型将多样化率与考虑异质性的非整倍性率联系起来，并区分前进演化和分支演化变化。我们将此模型应用于苔草属（莎草科），这是一个具有全着丝粒染色体的世界性开花植物分支。我们在苔草属中发现了两种不同的染色体进化和物种形成模式。在一种多样化模式中，非整倍性频繁发生并推动更快的多样化率。在另一种模式中，非整倍性很少见，多样化由隐藏的、未测量的因素驱动。当我们使用排除隐藏状态的模型时，我们错误地推断出非整倍性对多样化具有强烈的、一致的正向影响，这表明标准模型可能会导致关于多样化的看似确定但错误的结论。这项研究表明，尽管存在其他同时影响多样化的未测量因素，但非整倍性在一个大型植物分支的物种形成中可能具有重要作用。
