Larson Diane L, Pennarola Nora, Leone Julia B, Larson Jennifer L
U.S. Geological Survey, Northern Prairie Wildlife Research Center St. Paul Minnesota USA.
U.S. Fish and Wildlife Service Bloomington Minnesota USA.
Ecol Evol. 2024 Feb 26;14(2):e11036. doi: 10.1002/ece3.11036. eCollection 2024 Feb.
Reports increasingly point to substantial declines in wild bee abundance and diversity, yet there is uncertainty about how best to measure these attributes in wild bee populations. Two commonly used methods are passive trapping with bee bowls or active netting of bees on flowers, but each of these has drawbacks. Comparing the outcomes of the two methods is complicated by their uncomparable units of effort. The abundance distribution of bee species is also typically highly skewed, making it difficult to accurately assess diversity when rarer species are unlikely to be caught. The effective number of species, or Hill numbers, provides a way forward by basing the response metric on the number of equally abundant species. Our goal is to compare the effective number of bee species captured between hand netting and bowl trapping in wheatgrass prairie in South Dakota and tallgrass prairie in Minnesota, USA. Species overlap between the two methods ranged from ~40% to ~60%. Emphasis placed on rare species was important, so that 95% confidence limits overlapped between the two methods for species richness but netting exceeded trapping for Shannon's and Simpson's diversities. Netting always captured more bee species with fewer bee individuals than trapping. In most cases, the number of bees captured in bowl traps indicated substantial over-sampling, with little increase in bee species detected. Correlations between bee and floral abundance, richness, and diversity differed between netted and trapped samples. We conclude that netting and trapping together produce a more complete account of species richness, but shifting sampling emphasis from trapping to netting will result in fewer bees, but more bee species captured. Due to the different relationships between bee and floral diversities that depended on sampling method, it is unwise to compare habitat associations determined by netting with those determined by trapping.
越来越多的报告指出野生蜜蜂的数量和多样性大幅下降，但对于如何最好地衡量野生蜜蜂种群的这些属性仍存在不确定性。两种常用的方法是使用蜂碗进行被动诱捕或在花朵上对蜜蜂进行主动网捕，但每种方法都有缺点。由于两种方法的工作量单位不可比，比较它们的结果变得复杂。蜜蜂物种的丰度分布通常也高度偏态，这使得在不太可能捕获到稀有物种时难以准确评估多样性。有效物种数，即希尔数，通过将响应指标基于同等丰富度的物种数量提供了一条前进的道路。我们的目标是比较在美国南达科他州的小麦草草原和明尼苏达州的高草草原中，通过手网捕和碗诱捕所捕获的蜜蜂物种的有效数量。两种方法之间的物种重叠范围在约40%至约60%之间。对稀有物种的重视很重要，因此两种方法在物种丰富度上的95%置信区间重叠，但在香农多样性和辛普森多样性方面，网捕超过了诱捕。网捕总是比诱捕捕获更多的蜜蜂物种且个体数量更少。在大多数情况下，碗诱捕中捕获的蜜蜂数量表明存在大量的过度采样，检测到的蜜蜂物种增加很少。网捕和诱捕样本中蜜蜂与花卉的丰度、丰富度和多样性之间的相关性有所不同。我们得出结论，网捕和诱捕结合能更全面地反映物种丰富度，但将采样重点从诱捕转移到网捕会导致捕获的蜜蜂数量减少，但蜜蜂物种更多。由于蜜蜂与花卉多样性之间的关系因采样方法而异，将通过网捕确定的栖息地关联与通过诱捕确定的进行比较是不明智的。
