Carvajal Acosta Alma Nalleli, Formenti Ludovico, Godschalx Adrienne, Katsanis Angelos, Schapheer Constanza, Mooney Kailen, Villagra Cristian, Rasmann Sergio
Department of Entomology Michigan State University East Lansing Michigan USA.
Department of Ecology & Evolutionary Biology University of California, Irvine Irvine California USA.
Ecol Evol. 2023 Aug 16;13(8):e10418. doi: 10.1002/ece3.10418. eCollection 2023 Aug.
The diversity of specialized molecules produced by plants radiating along ecological gradients is thought to arise from plants' adaptations to local conditions. Therefore, closely related species growing in similar habitats should phylogenetically converge, or diverge, in response to similar climates, or similar interacting animal communities. We here asked whether closely related species in the genus (Asteraceae) growing within the same elevation bands in the Andes, converged to produce similar floral odors. To do so, we combine untargeted analysis of floral volatile organic compounds with insect olfactory bioassay in congeneric (Asteraceae) species growing within the same elevation bands along the Andean elevational gradient. We then asked whether the outcome of biotic interactions (i.e., pollination vs. seed predation) would also converge across species within the same elevation. We found that flower odors grouped according to their elevational band and that the main floral visitor preferred floral heads from low-elevation band species. Furthermore, the cost-benefit ratio of predated versus fertilized seeds was consistent within elevation bands, but increased with elevation, from 6:1 at low to 8:1 at high elevations. In the light of our findings, we propose that climate and insect community changes along elevation molded a common floral odor blend, best adapted for the local conditions. Moreover, we suggest that at low elevation where floral resources are abundant, the per capita cost of attracting seed predators is diluted, while at high elevation, sparse plants incur a higher herbivory cost per capita. Together, our results suggest that phytochemical convergence may be an important factor driving plant-insect interactions and their ecological outcomes along ecological gradients.
沿着生态梯度扩散的植物所产生的特殊分子的多样性被认为源于植物对当地环境的适应。因此，生长在相似栖息地的近缘物种在系统发育上应该会因相似的气候或相似的相互作用动物群落而趋同或趋异。我们在此探究了生长在安第斯山脉相同海拔带内的菊科同一属的近缘物种是否会趋同产生相似的花香气味。为此，我们将对花香挥发性有机化合物的非靶向分析与对沿安第斯海拔梯度生长在相同海拔带内的同属菊科物种进行的昆虫嗅觉生物测定相结合。然后我们探究了生物相互作用（即授粉与种子捕食）的结果在同一海拔的物种间是否也会趋同。我们发现花香气味根据其所在海拔带进行分组，并且主要的访花者更喜欢低海拔带物种的花头。此外，被捕食种子与受精种子的成本效益比在各海拔带内是一致的，但随着海拔升高而增加，从低海拔的6:1增加到高海拔的8:1。根据我们的研究结果，我们提出沿海拔变化的气候和昆虫群落塑造了一种最适合当地环境的常见花香混合气味。此外，我们认为在低海拔地区，花香资源丰富，吸引种子捕食者的人均成本被稀释，而在高海拔地区，植物稀少，人均食草成本更高。总之，我们的结果表明植物化学趋同可能是驱动植物 - 昆虫相互作用及其沿生态梯度的生态结果的一个重要因素。
