Abstract:
Ontogenetic shape change has long been recognized to be important in generating patterns of morphological diversity and may be especially important in plant reproductive structures. We explore how seed cone disparity in Cupressaceae changes over ontogeny by comparing pollination-stage and mature cones. We sampled cones at pollen and seed release and measured cone scales using basic morphometric shape variables. We used multivariate statistical methods, particularly hypervolume overlap calculations, to measure morphospace occupation and disparity. Cone scales at both pollination and maturity exhibit substantial variability, although the disparity is greater at maturity. Mature cone scales are also more clustered in trait space, showing less overlap with other taxa than at pollination. These patterns reflect two growth strategies that generate closed cones over maturation, either through thin laminar scales or relatively thick, peltate scales, resulting in two distinct regions of morphospace occupation. Disparity patterns in Cupressaceae seed cones change over ontogeny, reflecting shifting functional demands that require specific patterns of cone scale growth. The evolution of Cupressaceae reproductive disparity therefore represents selection for trajectories of ontogenetic shape change, a phenomenon that should be widespread across seed plants.
摘要:
长期以来,人们一直认为个体发育的形状变化在产生形态多样性的模式中很重要,并且在植物生殖结构中尤其重要。我们通过比较授粉期和成熟视锥细胞,探索柏科的种子视锥差异如何随个体发育而变化。我们在花粉和种子释放时对视锥进行采样,并使用基本的形态形状变量测量视锥尺度。我们使用多元统计方法,特别是超体积重叠计算,测量形态空间占用和差异。授粉和成熟时的锥形尺度都表现出很大的变异性,虽然在成熟时差距更大。成熟的锥尺度在特征空间中也更多地聚集,与授粉时相比,与其他类群的重叠较少。这些模式反映了两种生长策略,它们在成熟过程中产生封闭的锥体,要么通过薄的层状尺度,要么相对较厚,骨盆鳞片,导致两个不同的形态空间占用区域。柏科种子视锥的差异模式随着个体发育而变化,反映了需要特定锥形尺度增长模式的功能需求变化。因此,柏科生殖差异的进化代表了个体发育形状变化轨迹的选择,一种应该在种子植物中普遍存在的现象。