PDF(Pubmed)
Abstract：
Branching stipe morphologies have evolved multiple times across the kelp (Laminariales) lineage, creating morphological forms that drive the complexity of kelp forest habitats. Although branching is likely a complicated developmental process, it has evolved repeatedly through kelp evolution and the processes facilitating the emergence of branched forms from unbranched ancestors remain unclear. Here I report on abnormally branched individuals (n = 9) from five kelp species found in British Columbia, Canada that had atypical bifurcations in their stipes, creating a single dichotomous branch. One of these species generally lacks branching entirely (Laminaria ephemera) while the other four exhibit some branching but typically lack this stipe bifurcation (Alaria marginata, Laminaria setchellii, Nereocystis luetkeana, Pterygophora californica). These unusually branched individuals exhibited replicated morphological subunits distal to the stipe bifurcation, including more blades, pneumatocysts, and sporophylls than is typical. This suggests that unbranched species possess an inherent developmental capacity for modularity with autonomy in the development of individual modules that may have helped to facilitate the widespread emergence of branched morphologies. Given the role of kelp forests in coastal environments, branching may influence habitat characteristics, potentially influencing community dynamics, and is thus a trait of particular evolutionary interest. These findings highlight the need for experiments that manipulate kelp development to better characterise the ontogenetic processes of these globally important taxa.
摘要：
分支柄形态在海带（Laminariales）谱系中已经进化了多次，创造了推动海带森林栖息地复杂性的形态。虽然分支可能是一个复杂的发育过程，它通过海带的进化反复进化，促进无分支祖先分支形式出现的过程尚不清楚。在这里，我报告了不列颠哥伦比亚省发现的五种海带物种的异常分支个体（n=9），加拿大有非典型的分叉，创建一个单一的二分法分支。这些物种中的一个通常完全缺乏分支（Laminariaemphemera），而其他四个物种表现出一些分支，但通常缺乏这种柄分叉（Alariamarginata，海带，日耳虫囊,加州翼草）。这些异常分支的个体在柄分叉的远端表现出复制的形态亚基，包括更多的刀片，肺炎囊肿,和孢子体比典型的。这表明无分支物种具有内在的模块化发展能力，在单个模块的发展中具有自主性，这可能有助于促进分支形态的广泛出现。鉴于海带森林在沿海环境中的作用，分枝可能会影响生境特征，潜在影响社区动态，因此是一种具有特殊进化意义的特征。这些发现强调了需要进行操纵海带发育的实验，以更好地表征这些全球重要分类群的个体发育过程。
