Instituto Multidisciplinario de Biología Vegetal (IMBIV), CONICET-Universidad Nacional de Córdoba, Córdoba, 5000, Argentina.
Ann Bot. 2024 Nov 13;134(5):863-876. doi: 10.1093/aob/mcae122.
Diversity in pappus shapes and size in Asteraceae suggests an adaptive response to dispersion challenges adjusting diaspores to optimal phenotypic configurations. Here, by analysing the relationship among pappus-cypsela size relationships, flight performance and pappus types in an evolutionary context, we evaluate the role of natural selection acting on the evolution of diaspore configuration at a macro-ecological scale in the daisy family.
To link pappus-cypsela size relationships with flight performance we collected published data on these traits from 82 species. This allowed us to translate morphometric traits in flight performance for 150 species represented in a fully resolved backbone phylogeny of the daisy family. Through ancestral reconstructions and evolutionary model selection, we assessed whether flight performance was associated with and constrained by different pappus types. Additionally, we evaluated, through phylogenetic regressions, whether species with different pappus types exhibited evolutionary allometric pappus-cypsela size relationships.
The setose pappus type had the highest flight performances and represented the most probable ancestral state in the family. Stepwise changes in pappus types independently led from setose to multiple instances of pappus loss with associated reduction in flight performance. Flight performance evolution was best modelled as constrained by five adaptive regimes represented by specific pappus types which correspond to specific optimal diaspore configurations that are distinct in pappus-cypsela allometric relationships.
Evolutionary modelling suggests natural selection as the main factor of diaspore configuration changes which proceeded towards five optima, often overcoming constraints imposed by allometric relationships and favouring evolution in certain directions. With the perspective that natural selection is the main process driving the observed patterns, various biotic and abiotic are suggested as principal drivers of transitions in diaspore configurations along space and time in the daisy family history. The results also allow discussion of evolutionary changes in a historical context.
菊科植物的冠毛形状和大小的多样性表明，这是一种对散布挑战的适应性反应，使种籽适应最佳的表型结构。在这里，我们通过在进化背景下分析冠毛-瘦果大小关系、飞行性能和冠毛类型之间的关系，评估了在宏观生态尺度上自然选择对散布结构进化的作用。
为了将冠毛-瘦果大小关系与飞行性能联系起来，我们从 82 个物种中收集了这些性状的已发表数据。这使我们能够将 150 个物种的形态测量性状转换为菊科全分辨率骨干系统发育中的飞行性能。通过祖先重建和进化模型选择，我们评估了飞行性能是否与不同的冠毛类型相关，并受到其限制。此外，我们通过系统发育回归评估了具有不同冠毛类型的物种是否表现出进化的冠毛-瘦果大小的异速关系。
多毛冠毛类型具有最高的飞行性能，是该科最可能的祖先状态。冠毛类型的逐步变化独立地从多毛型到多个冠毛丧失的实例，导致飞行性能降低。飞行性能的进化最好被建模为受到五个适应性机制的限制，这五个适应性机制由特定的冠毛类型代表，与不同的冠毛-瘦果的异速关系相区别，反映了不同的最佳种籽配置。
进化模型表明，自然选择是种籽配置变化的主要因素，这些变化朝着五个最优方向发展，通常克服了异速关系的限制，并有利于某些方向的进化。从自然选择是驱动观察模式的主要过程的角度来看，各种生物和非生物因素被认为是菊科历史中沿空间和时间散布配置转变的主要驱动因素。研究结果还允许从历史背景讨论进化变化。
