Simon Sandra J, Keefover-Ring Ken, Park Yong-Lak, Wimp Gina, Grady Julianne, DiFazio Stephen P
Department of Biology West Virginia University Morgantown WV USA.
Departments of Botany and Geography University of Wisconsin-Madison Madison WI USA.
Ecol Evol. 2021 Mar 18;11(9):4688-4700. doi: 10.1002/ece3.7369. eCollection 2021 May.
(black willow) is a widespread tree that hosts many species of polylectic hymenopterans and oligolectic bees of the genus . The early flowering of makes it an important nutritive resource for arthropods emerging from hibernation. However, since is dioecious, not all insect visits will lead to successful pollination. Using both visual observation and pan-trapping, we characterized the community of arthropods that visited flowers and assessed differences among male and female trees as well as the chemical and visual drivers that influenced community composition across 3 years. We found that male trees consistently supported higher diversity of insects than female trees and only three insect species, all spp., consistently visited both sexes. Additionally, , which was the only insect that occurred more on female than male flowers, correlated strongly to volatile cues. This suggests that cross-pollinators cue into specific aspects of floral scent, but diversity of floral visitors is driven strongly by visual cues of yellow male pollen. Through time, the floral activity of two species remained stable, but visited less in 2017 when flowers bloomed earlier than other years. When native bee emergence does not synchronize with bloom, activity appears to be diminished which could threaten species that subsist on a single host. Despite the community diversity of flowers, its productivity depends on a small fraction of species that are not threatened by competition, but rather rapidly changing conditions that lead to host-insect asynchrony.
（黑柳）是一种分布广泛的树木，为许多多食性膜翅目昆虫和寡食性蜜蜂属的蜜蜂提供栖息地。黑柳的早花使其成为从冬眠中苏醒的节肢动物的重要营养资源。然而，由于黑柳是雌雄异株，并非所有昆虫的访花行为都会导致成功授粉。我们通过视觉观察和泛陷阱诱捕两种方法，对访花节肢动物群落进行了特征描述，并评估了雄树和雌树之间的差异，以及在三年时间里影响群落组成的化学和视觉驱动因素。我们发现，雄树始终比雌树支持更高的昆虫多样性，并且只有三种昆虫物种（均为 属）始终会访问两性花朵。此外， 是唯一在雌花上出现数量多于雄花的昆虫，它与挥发性线索密切相关。这表明异花传粉者会对花香的特定方面产生反应，但访花者的多样性在很大程度上是由黄色雄花花粉的视觉线索驱动的。随着时间的推移，两种 物种的花期活动保持稳定，但在 2017 年，当花朵比其他年份更早开放时， 访花的数量减少。当本地蜜蜂的出现与花期不同步时，活动似乎会减少，这可能会威胁到依赖单一寄主生存的物种。尽管黑柳花朵的群落具有多样性，但其生产力取决于一小部分不受竞争威胁的物种，而是取决于导致寄主与昆虫不同步的快速变化的条件。
