Data from: Three's a crowd: trade-offs between attracting pollinators and ant bodyguards with nectar rewards in Turnera

Many plants attract insect pollinators with floral nectar (FN) and ant "bodyguards" with extrafloral nectar (EFN). If nectar production is costly or physiologically linked across glands, investment in one mutualism may trade off with investment in the other. We confirmed that changes in FN and EFN availability alter pollination and ant defense mutualisms in a field population of T. ulmifolia. Plants with additional FN tended to produce more seeds, while plants with reduced EFN production experienced less florivory. We then mimicked the consumptive effects of mutualists by removing FN or EFN daily for 50 days in a full factorial design using three Turnera species (T. joelii, T. subulata, and T. ulmifolia) in a glasshouse experiment. For T. ulmifolia and T. subulata, but not T. joelii, removing either nectar reduced production of the other, showing for the first time that EFN and FN production can trade off. In T. subulata, increased investment in FN decreased seed set, suggesting that nectar production can have direct fitness costs. Through the linked expression of EFN and FN, floral visitors may negatively affect biotic defense, and extrafloral nectary visitors may negatively affect pollination. 25 pages, 5 figures; Appendix诸多植物通过花内花蜜（floral nectar, FN）吸引昆虫传粉者，并以花外花蜜（extrafloral nectar, EFN）招募蚂蚁作为“保镖”。若花蜜合成存在代谢成本，或不同蜜腺间存在生理关联，则对其中一种互利共生关系的投入，可能与对另一种的投入形成权衡。本研究证实，在野外种群的T. ulmifolia中，花内花蜜与花外花蜜的可获得性变化，会改变其传粉与蚂蚁防御两类互利共生关系：施加额外花内花蜜的植株结籽量更高，而花外花蜜合成受抑制的植株则受花部植食为害的程度更低。随后，本研究通过温室实验，采用完全析因设计，每日移除花内花蜜或花外花蜜，持续50天，以此模拟互利共生者的消耗效应，实验对象为三种特纳草属（Turnera）植物：T. joelii、T. subulata与T. ulmifolia。实验结果显示，仅在T. ulmifolia与T. subulata（而非T. joelii）中，移除任意一种花蜜都会降低另一种的合成量，这首次证实花外花蜜与花内花蜜的合成存在权衡关系。在T. subulata中，提高花内花蜜的投入会降低结籽率，这表明花蜜合成存在直接的适合度代价。由于花内花蜜与花外花蜜的表达存在关联，传粉昆虫可能会对生物防御产生负面影响，而访问花外蜜腺的昆虫则可能对传粉过程产生负面影响。全文共25页，含5幅图；附附录