PNAS：热带植物识别不同的传粉者
一项研究描述了一种热带植物区别访问它的花的传粉者，让繁殖主要由最可能携带高质量花粉的传粉者进行。
Matthew Betts及其同事研究了热带植物Heliconia tortuosa，它进化出了长的管状花，被认为用于吸引特定的传粉者。至少有6种喙形不同的蜂鸟物种访问这个植物。
这组作者用实验比较了在有控制的条件下这些蜂鸟的传粉成功，结果发现，与直喙的陆地鸟类或昆虫相比，对于经过远距离旅行访问植物的蜂鸟物种，这种植物的繁殖“启动”到了更大的程度。由于高质量花粉可能来自遥远地方的没有亲缘关系的植物，这些发现提示这些植物可能识别有可能携带最佳花粉的鸟类物种。
进一步的实验证明了这些植物使用花蜜提取功能——它是鸟喙长度的一个直接函数——识别花的访问者， 而接受研究的这6个蜂鸟物种只有2种对于这种植物的繁殖具有有意义的贡献。
这组作者说，这些发现提示，过滤传粉者可能促进高度多样的植物-传粉者网络之间的共同进化，但是也可能让传粉容易受到环境变化的伤害。
原文链接：Pollinator recognition by a keystone tropical plant
Understanding the mechanisms enABLing coevolution in complex mutualistic networks remains a central challenge in evolutionary biology. We show for the first time, to our knowledge, that a tropical plant species has the capacity to discriminate among floral visitors, investing in reproduction differentially across thepollinator community. After we standardized pollen quality in 223 aviary experiments, successful pollination of Heliconia tortuosa (measured as pollen tube abundance) occurred frequently when plants were visitedby long-distance traplining hummingbird species with specialized bills (x¯ pollen tubes = 1.21 ± 0.12 SE) but was reduced 5.7 times when visited by straight-billed territorial birds (x¯ pollen tubes = 0.20 ± 0.074 SE) or insects. Our subsequent experiments revealed that plants use the nectar extraction capacity of tropicalhummingbirds, a positive function of bill length, as a cue to turn on reproductively. Furthermore, we show that hummingbirds with long bills and high nectar extraction efficiency engaged in daily movements at broad spatial scales (∼1 km), but that territorial species moved only short distances (<100 m). Such pollinatorrecognition may therefore affect mate selection and maximize receipt of high-quality pollen from multiple parents. Although a diffuse pollinator network is implied, because all six species of hummingbirds carry pollen of H. tortuosa, only two species with specialized bills contribute meaningfully to its reproduction. We hypothesize that this pollinator filtering behavior constitutes a crucial mechanism facilitating coevolution in multispecies plant–pollinator networks. However, pollinator recognition also greatly reduces the number of realized pollinators, thereby rendering mutualistic networks more vulnerable to environmental change.
doi: 10.1073/PNAS.1419522112
作者：Matthew G. Betts
