Signal honesty and cost of pollinator rewards in Dalechampia scandens (Euphorbiaceae).
Signal honesty and cost of pollinator rewards in Dalechampia scandens (Euphorbiaceae).
复制标题
大戟科（大戟科）传粉者奖励的信号诚实和成本。
作者：
C. Pélabon;Patrick Thöne;T. F. Hansen;W. Armbruster
背景和目标
大多数 Dalechampia 藤本植物（大戟科）通过花序中的腺状结构分泌的萜类树脂来吸引蜜蜂传粉者。在某些物种中，授粉蜜蜂似乎优先访问具有大型树脂生产腺体的花序（花朵），而在其他物种中，蜜蜂优先访问具有大型总苞片的花朵。在这项研究中，评估了苞片和腺体大小作为一种物种（D. scandens）产生的树脂量信号的可靠性。还检查了树脂分泌是否会影响花朵产生的种子的数量或质量。
方法
测量了共同环境中的花的苞片大小、腺体大小和分泌的树脂量，并分析了这些性状之间的关系。还对树脂生产进行了控制，并测试了控制对种子结实率和种子质量的影响。
主要成果
通过腺体的大小比通过苞片的大小可以更好地预测所产生的树脂量。此外，当考虑腺体大小的影响时，苞片大小只能微弱地预测树脂产生量。树脂分泌的增加（通过每天去除树脂）和减少（通过去除树脂腺）均不会对种子结实或种子质量产生可检测的影响，但一旦考虑了树脂腺的大小，树脂产量与个体水平的平均种子质量呈正相关。
结论
腺体大小比苞片大小更能反映奖励量，尽管后者仍然是产生树脂量的真实信号。就种子生产而言，树脂分泌没有可检测到的成本，但可能取决于条件，如个体水平上与种子质量的正相关所表明的那样。
BACKGROUND AND AIMS
Most species of Dalechampia vines (Euphorbiaceae) attract bee pollinators with terpenoid resins secreted by a gland-like structure in the inflorescence. In some species, pollinating bees appear to preferentially visit inflorescences (blossoms) with large resin-producing glands, whereas in other species bees preferentially visit blossoms with large involucral bracts. In this study, the reliability of bract and gland size as signals of the quantity of resin produced in one species, D. scandens, was assessed. Whether resin secretion has a cost with respect to the number or mass of the seeds produced by a blossom was also examined.
METHODS
Measurements were made of bract size, gland size and the amount of resin secreted by blossoms of D. scandens maintained in a common environment, and the relationships between these traits were analysed. Resin production was also manipulated, and the effects of the manipulation were tested on seed set and seed mass.
KEY RESULTS
The amount of resin produced was better predicted by the size of the gland than by the size of the bract. Furthermore, when the effect of gland size was accounted for, bract size only weakly predicted the amount of resin produced. Neither an increase in resin secretion (by daily removal of the resin) nor a decrease (by removal of the resin gland) affected seed set or seed mass detectably, but resin production correlated positively with mean seed mass at the individual level once the size of the resin gland was accounted for.
CONCLUSIONS
Gland size is a better indicator of the amount of reward than bract size, although the latter remained an honest signal of the quantity of resin produced. Resin secretion has no detectable cost in terms of seed production, but may be condition dependent, as suggested by a positive correlation with seed mass at the individual level.