Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki, Kyoto 606-8585, Japan.
J Plant Res. 2009 Mar;122(2):183-92. doi: 10.1007/s10265-008-0204-6. Epub 2008 Dec 26.
This study investigated floral visitations of two beetles, Parastasia bimaculata (Scarabaeidae) and Chaloenus schawalleri (Chrysomelidae), and examined associations between beetle visitations and variation in attractant traits, such as quantitative variations of attractants in floral odors and heat generation of spadices in Homalomena propinqua (Araceae). Observations showed P. bimaculata visited pistillate-phase inflorescences most frequently during heat generation, whereas C. schawalleri visited regardless of floral stages and heat generation. Chemical analyses of five dominant components of floral odors showed quantities of 2-butanol, veratrole, and alpha-pinene during the pistillate phase were the most abundant during all floral stages, and increased during heat generation. When testing combinations of these five authentic chemicals, some mixtures including 2-butanol or veratrole or both attracted both beetles, and veratrole attracted C. schawalleri. These results strongly suggested that the increased emission of floral odor attractants which accompanied heat generation influences floral visitations by P. bimaculata, but not by C. schawalleri. We therefore hypothesize that P. bimaculataaculata is a reliable pollinator, and that variation in attractant traits is a honest signal for P. bimaculata to seek rewards. In contrast, C. schawalleri can detect the signal even at low levels, and so visits inflorescences steadily during all floral stages.
本研究调查了两种甲虫，Parastasia bimaculata（鞘翅目）和 Chaloenus schawalleri（叶甲科）的访花行为，并研究了甲虫访花与引诱特征变化之间的关系，如花的气味中引诱剂的数量变化和 Homalomena propinqua（天南星科）的佛焰苞产热。观察结果表明，P. bimaculata 在产热时最常访问雌蕊相花序，而 C. schawalleri 则无论花朵阶段和产热情况如何都会访问。对五种主要花香成分的化学分析表明，在雌蕊相期间，2-丁醇、藜芦醚和α-蒎烯的数量在所有花朵阶段最为丰富，并在产热期间增加。在测试这五种天然化学物质的混合物时，包括 2-丁醇或藜芦醚或两者的混合物都吸引了这两种甲虫，而藜芦醚吸引了 C. schawalleri。这些结果强烈表明，伴随着产热而增加的花香引诱剂的释放会影响 P. bimaculata 的访花行为，但不会影响 C. schawalleri。因此，我们假设 P. bimaculataaculata 是一种可靠的传粉者，而引诱特征的变化是 P. bimaculata 寻找奖励的诚实信号。相比之下，C. schawalleri 即使在低水平也能检测到信号，因此在所有花朵阶段都能稳定地访问花序。
