Departamento de Biología, Universidad de La Serena, La Serena, Chile.
Oecologia. 2013 Sep;173(1):13-21. doi: 10.1007/s00442-013-2590-2. Epub 2013 Jan 19.
Several studies across species have linked leaf functional traits with shade tolerance. Because evolution by natural selection occurs within populations, in order to explain those interspecific patterns it is crucial to examine variation of traits associated with shade tolerance and plant fitness at an intraspecific scale. In a southern temperate rainforest, two climbing plant species coexist but differ in shade tolerance. Whereas Luzuriaga radicans is most abundant in the shaded understory, L. polyphylla typically occurs in intermediate light environments. We carried out an intraspecific approach to test the hypothesis of differential selection patterns in relation to shade tolerance in these congeneric species. The probability of showing reproductive structures increased with specific leaf area (SLA) in L. polyphylla, and decreased with dark respiration in L. radicans. When reproductive output of fertile individuals was the fitness variable, we detected positive directional selection on SLA in L. polyphylla, and negative directional selection on dark respiration and positive directional selection on leaf size in L. radicans. Total light radiation differed between the microsites where the Luzuriaga species were sampled in the old-growth forest understory. Accordingly, L. radicans had a lower minimum light requirement and showed fertile individuals in darker microsites. L. radicans showed lower dark respiration, higher chlorophyll content, and greater leaf size and SLA than L. polyphylla. Results suggest that in more shade-tolerant species, established in the darker microsites, selection would favor functional traits minimizing carbon losses, while in less shade-tolerant species, plants displaying leaf traits enhancing light capture would be selected.
已有多项跨物种的研究将叶片功能性状与耐荫性联系起来。由于自然选择的进化是在种群内部发生的，因此要解释这些种间模式，关键是要在种内尺度上研究与耐荫性和植物适应性相关的性状变化。在南温带雨林中，两种攀援植物共存，但耐荫性不同。Luzuriaga radicans 在阴暗的林下最为丰富，而 L. polyphylla 则通常出现在中等光照环境中。我们进行了种内研究，以检验这两个同属物种与耐荫性相关的差异选择模式的假设。在 L. polyphylla 中，具有特定叶面积（SLA）的个体出现繁殖结构的概率增加，而在 L. radicans 中，黑暗呼吸速率降低。当有性繁殖个体的生殖输出是适应性变量时，我们在 L. polyphylla 中检测到对 SLA 的正向定向选择，在 L. radicans 中检测到对黑暗呼吸的负向定向选择和对叶片大小的正向定向选择。在成熟林林下采集 Luzuriaga 物种的微生境之间，总光辐射存在差异。因此，L. radicans 的最低光需求较低，在较暗的微生境中表现出有性繁殖个体。L. radicans 的黑暗呼吸率较低，叶绿素含量较高，叶片大小和 SLA 较大，均高于 L. polyphylla。结果表明，在较耐荫的物种中，它们在较暗的微生境中建立起来，选择会有利于最小化碳损失的功能特征，而在较不耐荫的物种中，选择的是那些能够提高光捕获的叶片特征。
