Thorson’s rule, life history evolution and diversification of benthic octopuses (Cephalopoda: Octopodoidea)

Here we evaluate the so-called Thorson’s rule, which posits that direct-development and larger eggs are favored towards the poles in marine organisms and whose validity been the subject of considerable debate in the literature, combining an expanded phenotypic dataset encompassing 60 species of benthic octopuses with a new molecular phylogeny. Phylogenetic reconstruction shows two clades: clade 1 including species of the families Eledonidae, Megaleledonidae, Bathypolypodidae and Enteroctopodidae, and clade 2 including species of Octopodidae. Egg size, development mode and all environmental variables exhibited phylogenetic signal, partly due to differences between the two clades: whereas most species in clade 1 inhabit cold and deep waters, exhibit large eggs and hatchling with holobenthic development, species from clade 2 inhabit tropical-temperate and shallow waters, evolved small eggs and generally exhibit merobenthic development. Phylogenetic regressions show that egg size exhibits a...本研究旨在评估所谓的索尔松法则（Thorson's rule），该法则提出海洋生物中直接发育与大型卵在极地环境中更具选择优势，其有效性在学界一直存在广泛争议。本研究结合了涵盖60种底栖章鱼的扩展表型数据集与全新的分子系统发育（molecular phylogeny）分析数据。系统发育重建结果显示存在两个演化支：演化支1包含电蛸科（Eledonidae）、巨体蛸科（Megaleledonidae）、深潜蛸科（Bathypolypodidae）以及肠蛸科（Enteroctopodidae）的物种，演化支2则包含蛸科（Octopodidae）的物种。卵大小、发育模式以及所有环境变量均表现出系统发育信号（phylogenetic signal），这一现象在一定程度上源于两个演化支之间的差异：演化支1的多数物种栖息于寒冷深水水域，产下大型卵且孵化幼体为全底栖发育（holobenthic development）；而演化支2的物种多栖息于热带-温带浅水环境，演化出小型卵，且通常表现为半底栖发育（merobenthic development）。系统发育回归分析显示，卵大小呈现出……