Data from: Keeping an eye on coloration: ecological correlates of the evolution of pitcher traits in the genus Nepenthes (Caryophyllales)

Nepenthes is a genus of carnivorous pitcher plants with high intra- and interspecific morphological diversity. Many species produce dimorphic pitchers, and the relative production rate of the two morphs varies interspecifically. Despite their likely ecological importance to the plants, little is known about the selective context under which various pitcher traits have evolved. This is especially true of color-related traits, which have not been examined in a phylogenetic context. Using field observations of one polymorphic species (N. gracilis) and phylogenetic comparative analysis of 85 species across the genus, we investigate correlations between color polymorphism and ecological factors including altitude, light environment, and herbivory. In N. gracilis, color does not correlate to amount of prey-capture, but red pitchers experience less herbivory. Throughout the genus, color polymorphism with redder lower pitchers appears to be evolutionarily favored. We found a lack of phylogenetic signal for most traits, either suggesting that most traits are labile or reflecting the uncertainty regarding the underlying tree topology. This work highlights ecological correlates of the vast phenotypic diversity of this group of tropical plants. We point to a need for future work examining herbivores of Nepenthes and experimental investigations on color polymorphism.

猪笼草属（Nepenthes）是一类食肉食虫植物，种内与种间形态多样性水平极高。诸多物种可产生二型捕虫笼，两种形态的相对产出率存在显著种间差异。尽管这些性状对植株可能具有重要的生态意义，但学界对各类捕虫笼性状演化的选择背景仍知之甚少，与颜色相关的性状更是如此——此前尚未有研究在系统发育框架下对其展开探讨。本研究通过对多态性物种瘦小猪笼草（N. gracilis）的野外观测，以及对该属85个物种的系统发育比较分析，探讨了颜色多态性与海拔、光照环境、植食压力等生态因子之间的相关性。在瘦小猪笼草中，捕虫笼颜色与猎物捕获量并无关联，但红色捕虫笼遭受的植食危害更低。针对整个猪笼草属的分析显示，具有更偏红色下位捕虫笼的颜色多态性似乎在演化进程中更受青睐。本研究发现多数性状缺乏系统发育信号，这要么表明多数性状具有较高的演化可塑性，要么反映了当前系统发育树拓扑结构的不确定性。本研究揭示了这类热带植物庞大表型多样性背后的生态关联因子，并指出未来亟需开展猪笼草植食动物相关研究以及颜色多态性的实验验证工作。