Desert Ecology Research Group, School of Biological Sciences, The University of Sydney, Sydney, New South Wales, Australia.
PLoS One. 2013 Jun 17;8(6):e66665. doi: 10.1371/journal.pone.0066665. Print 2013.
Methods for sampling ecological assemblages strive to be efficient, repeatable, and representative. Unknowingly, common methods may be limited in terms of revealing species function and so of less value for comparative studies. The global decline in pollination services has stimulated surveys of flower-visiting invertebrates, using pan traps and net sampling. We explore the relative merits of these two methods in terms of species discovery, quantifying abundance, function, and composition, and responses of species to changing floral resources. Using a spatially-nested design we sampled across a 5000 km(2) area of arid grasslands, including 432 hours of net sampling and 1296 pan trap-days, between June 2010 and July 2011. Net sampling yielded 22% more species and 30% higher abundance than pan traps, and better reflected the spatio-temporal variation of floral resources. Species composition differed significantly between methods; from 436 total species, 25% were sampled by both methods, 50% only by nets, and the remaining 25% only by pans. Apart from being less comprehensive, if pan traps do not sample flower-visitors, the link to pollination is questionable. By contrast, net sampling functionally linked species to pollination through behavioural observations of flower-visitation interaction frequency. Netted specimens are also necessary for evidence of pollen transport. Benefits of net-based sampling outweighed minor differences in overall sampling effort. As pan traps and net sampling methods are not equivalent for sampling invertebrate-flower interactions, we recommend net sampling of invertebrate pollinator assemblages, especially if datasets are intended to document declines in pollination and guide measures to retain this important ecosystem service.
方法学采样生态组合力求高效、可重复且具代表性。不经意间，常用的方法可能在揭示物种功能方面受到限制，因此在比较研究中价值较低。授粉服务的全球衰退刺激了对访花无脊椎动物的调查，使用了 Pan 陷阱和网采样。我们根据物种发现、定量丰度、功能和组成以及物种对变化的花卉资源的响应，来探索这两种方法的相对优点。使用空间嵌套设计，我们在 5000 平方公里的干旱草原地区进行了采样，包括 2010 年 6 月至 2011 年 7 月期间的 432 小时网采样和 1296 个 Pan 陷阱日。网采样比 Pan 陷阱多发现 22%的物种和 30%的丰度，并且更好地反映了花卉资源的时空变化。物种组成在方法之间存在显著差异；在 436 种总物种中，有 25%被两种方法同时采样，50%仅用网采样，其余 25%仅用 Pan 陷阱采样。如果 Pan 陷阱没有采样到访花者，除了不够全面之外，与授粉的联系也值得怀疑。相比之下，网采样通过对访花行为观察到的花-访客相互作用频率，将物种与授粉联系起来。有网采样的标本也必须有花粉运输的证据。基于网采样的好处超过了总体采样努力的微小差异。由于 Pan 陷阱和网采样方法在采样无脊椎动物-花相互作用方面并不等同，我们建议对无脊椎动物授粉者组合进行网采样，特别是如果数据集旨在记录授粉的下降并指导保留这一重要生态系统服务的措施。
