Natural History Museum, University of Oslo, Oslo, Norway.
Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Oslo, Norway.
Proc Biol Sci. 2021 Jan 27;288(1943):20202047. doi: 10.1098/rspb.2020.2047. Epub 2021 Jan 20.
Long-term patterns of phenotypic change are the cumulative results of tens of thousands to millions of years of evolution. Yet, empirical and theoretical studies of phenotypic selection are largely based on contemporary populations. The challenges in studying phenotypic evolution, in particular trait-fitness associations in the deep past, are barriers to linking micro- and macroevolution. Here, we capitalize on the unique opportunity offered by a marine colonial organism commonly preserved in the fossil record to investigate trait-fitness associations over 2 Myr. We use the density of female polymorphs in colonies of as a proxy for fecundity, a fitness component, and investigate multivariate signals of trait-fitness associations in six time intervals on the backdrop of Pleistocene climatic shifts. We detect negative trait-fitness associations for feeding polymorph (autozooid) sizes, positive associations for autozooid shape but no particular relationship between fecundity and brood chamber size. In addition, we demonstrate that long-term trait patterns are explained by palaeoclimate (as approximated by ∂O), and to a lesser extent by ecological interactions (i.e. overgrowth competition and substrate crowding). Our analyses show that macroevolutionary outcomes of trait evolution are not a simple scaling-up from the trait-fitness associations.
长期的表型变化模式是数万年至数百万年进化的累积结果。然而，表型选择的实证和理论研究在很大程度上基于当代种群。研究表型进化，特别是在远古时期的特征与适应性关联的挑战，是将微观进化和宏观进化联系起来的障碍。在这里，我们利用在化石记录中普遍保存的海洋群居生物提供的独特机会，研究了超过 200 万年的特征与适应性关联。我们使用 的多态雌性个体的密度作为生殖力的一个指标，这是一个适应性组成部分，并在 6 个时间间隔内，在更新世气候变化的背景下，调查了特征与适应性关联的多元信号。我们检测到摄食多态（自体）体型与生殖力呈负相关，自体体型与生殖力呈正相关，但生殖力与育室大小之间没有特定关系。此外，我们证明了长期的特征模式是由古气候（如 ∂O 所近似）解释的，在较小程度上是由生态相互作用（即过度生长竞争和基质拥挤）解释的。我们的分析表明，特征进化的宏观进化结果不是从特征与适应性关联简单地放大而来的。
