Plant toxin levels in nectar vary spatially across native and introduced populations
Plant toxin levels in nectar vary spatially across native and introduced populations
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DOI：
10.1111/1365-2745.12573
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发表时间：
2016-07-01
影响因子：
5.5
通讯作者：
Stout, Jane C.
中科院分区：
文献类型：
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作者：
Egan, Paul A.;Stevenson, Phillip C.;Stout, Jane C.
花蜜中的次生化合物可以作为有毒的化学防御对花的拮抗剂，但也可以介导植物传粉者的相互作用。尽管它们的生态重要性，很少有研究调查有毒花蜜化合物在植物物种的空间变异模式，没有超出其原生范围。灰蝶毒素I（GTX I）存在于入侵的高山杜鹃花蜜中，对蜜蜂和一些独居蜜蜂有毒。我们研究了（i）花蜜GTX I的组成的地理变异，以及GTX III（这是没有毒性的这些物种），在本地和引进的范围R.ponticum，（ii）他们的表达是如何在补丁和景观尺度范围内的结构，以及（iii）是否气候和环境因素支撑空间格局。虽然两种GTX在范围内变化，但在范围之间检测到GTX I的变化，而不是GTX III。因此，GTX I表达显着降低或（在18%的情况下）在引进植物花蜜缺席。空间自相关是明显的斑块和景观尺度和部分相关的热负荷拦截植物（纬度，坡向和坡度的函数）。由于花蜜GTX的表达通常对环境变化具有鲁棒性，并且在空间上聚集，因此这种特性具有被消费者空间区分的潜力。鉴于GTX I变化的特异性及其对某些蜜蜂物种的不同毒性，我们得出结论，其表达可能在入侵期间受到与食草动物/消费者相互作用的影响，无论是通过传粉媒介介导的选择还是从花拮抗剂释放的敌人。作为有毒花蜜化合物的大规模地理变异和空间结构的第一个示范，这项工作加深了我们对本地和引进物种花相互作用的化学生态学的理解。花蜜次生化合物的空间明确的研究，因此需要显示空间变异的程度和结构可能会影响花生态。入侵理论的未来发展应该包括一个整体的观点，植物防御，超越拮抗作用，整合化学防御互惠回报的后果。
Secondary compounds in nectar can function as toxic chemical defences against floral antagonists, but may also mediate plant-pollinator interactions. Despite their ecological importance, few studies have investigated patterns of spatial variation in toxic nectar compounds in plant species, and none outside their native range. Grayanotoxin I (GTX I) occurs in nectar of invasive Rhododendron ponticum where it is toxic to honeybees and some solitary bee species. We examined (i) geographic variation in the composition of nectar GTX I, as well as GTX III (which is not toxic to these species), in the native and introduced range of R.ponticum, (ii) how their expression is structured at patch and landscape scales within ranges, and (iii) whether climatic and environmental factors underpin spatial patterns. While both GTXs varied within ranges, variation in GTX I, but not GTX III, was detected between ranges. GTX I expression was thus markedly lower or (in 18% of cases) absent from nectar in introduced plants. Spatial autocorrelation was apparent at both patch and landscape scales and in part related to heat load interception by plants (a function of latitude, aspect and slope). As expression of nectar GTXs was generally robust to environmental variation, and aggregated in space, this trait has the potential to be spatially discriminated by consumers. Given the specificity of change to GTX I, and its differential toxicity to some bee species, we conclude that its expression was likely to have been influenced during invasion by interaction with herbivores/consumers, either via pollinator-mediated selection or enemy release from floral antagonists.Synthesis. As the first demonstration of large-scale geographic variation and spatial structure in toxic nectar compounds, this work deepens our understanding of the chemical ecology of floral interactions in native and introduced species. Spatially explicit studies of nectar secondary compounds are thus required to show how the extent and structure of spatial variation may affect floral ecology. Future development of invasion theory should incorporate a holistic view of plant defence, beyond antagonistic interactions, which integrates the consequences of chemically defended mutualist rewards.