Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Am Nat. 2013 Feb;181(2):273-81. doi: 10.1086/668819. Epub 2012 Dec 26.
Adult leaf fenestration in "Swiss cheese" plants (Monstera Adans.) is an unusual leaf shape trait lacking a convincing evolutionary explanation. Monstera are secondary hemiepiphytes that inhabit the understory of tropical rainforests, where photosynthesis from sunflecks often makes up a large proportion of daily carbon assimilation. Here I present a simple model of leaf-level photosynthesis and whole-plant canopy dynamics in a stochastic light environment. The model demonstrates that leaf fenestration can reduce the variance in plant growth and thereby increase geometric mean fitness. This growth-variance hypothesis also suggests explanations for conspicuous ontogenetic changes in leaf morphology (heteroblasty) in Monstera, as well as the absence of leaf fenestration in co-occurring juvenile tree species. The model provides a testable hypothesis of the adaptive significance of a unique leaf shape and illustrates how variance in growth rate could be an important factor shaping plant morphology and physiology.
成年叶片开窗在“瑞士奶酪”植物（龟背竹属）中是一种不常见的叶片形状特征，缺乏令人信服的进化解释。龟背竹是次生半附生植物，栖息在热带雨林的林下，那里的阳光光斑光合作用常常构成了每日碳同化的很大一部分。在这里，我提出了一个在随机光照环境下的叶片水平光合作用和整个植物冠层动态的简单模型。该模型表明，叶片开窗可以减少植物生长的方差，从而增加几何平均适应度。这种生长方差假说也为龟背竹中明显的叶片形态发生变化（异形叶性）以及在共存的幼年树种中没有叶片开窗提供了解释。该模型为独特叶片形状的适应性意义提供了一个可测试的假说，并说明了生长速度的方差如何成为塑造植物形态和生理学的一个重要因素。
