Data from: Changing light conditions in pine rockland habitats affect the intensity and outcome of ant–plant interactions

Extrafloral nectar (EFN) mediates food-for-protection mutualisms between plants and ants. Such mutualisms exist within a complex web of biotic interactions, and in a framework provided by the abiotic environment. Both biotic and abiotic factors, therefore, affect the outcome of ant–plant interactions. We conducted an experiment to determine the effects of ant activity, and light intensity, on herbivory rates, growth, and reproductive fitness in Senna mexicana var. chapmanii, a perennial legume native to pine rockland habitats of south Florida. Forty plants were divided among four treatments in a factorial experimental design with two independent variables: ant activity and light intensity. Plants were divided equally between sunny and shady habitats, and ants were excluded from half of the plants in each habitat type. The presence of ants significantly reduced herbivory rates in S. chapmanii. In shaded habitats, the presence of ants had no effect on plant reproductive fitness, however, in sunny habitats plants with ants produced significantly more seeds over the duration of the 1-yr study. Ants represent an important biotic defense against herbivores in S. chapmanii; however, their effects on plant fitness are dependent on light conditions. Pine rockland habitats in south Florida have been widely destroyed or mismanaged. In fragments that remain, suppression of fire has led to increased canopy closure and shading of the understory. These changes will likely negatively impact plants that rely on ants for defense. We highlight the importance of conservation efforts to preserve the pine rocklands and the fire regimes on which they rely.

花外蜜腺（Extrafloral Nectar, EFN）介导植物与蚂蚁间的食物-保护互惠共生关系。此类互惠共生关系嵌于复杂的生物交互网络之中，其存续依托于非生物环境所构建的框架。因此，生物与非生物因子共同影响着蚁植交互的结果。本研究开展了一项实验，旨在探究蚂蚁活动与光照强度对查普曼番泻豆（Senna mexicana var. chapmanii）——一种原生分布于南佛罗里达松岩生境的多年生豆科植物——的植食率、生长状况及繁殖适合度的影响。实验采用包含两个自变量（蚂蚁活动与光照强度）的析因实验设计，将40株供试植物划分为4个处理组：供试植物被均匀分配至向阳与遮阴两种生境中，且每种生境类型下的半数植株均被阻断蚂蚁访问。研究结果显示，蚂蚁的存在显著降低了S. chapmanii的植食率。在遮阴生境中，蚂蚁的存在对植物繁殖适合度无显著影响；然而在向阳生境中，有蚂蚁伴生的植株在为期1年的研究周期内结出的种子量显著更高。蚂蚁是S. chapmanii抵御植食者的重要生物防御因子，但其对植物适合度的影响依赖于光照条件。南佛罗里达的松岩生境已遭到大范围破坏或不当管理。在现存的生境片段中，对野火的抑制导致林冠郁闭度提升，进而使林下生境更为遮阴。这些变化大概率会对依赖蚂蚁进行防御的植物产生负面影响。本研究强调了保护松岩生境及其依赖的野火动态的保育工作的重要性。