Kaçar Gülay, Wang Xin-Geng, Biondi Antonio, Daane Kent M
Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, United States of America.
PLoS One. 2017 Aug 22;12(8):e0183525. doi: 10.1371/journal.pone.0183525. eCollection 2017.
Functional response describes the number of prey or hosts attacked by a predator or parasitoid as a function of prey or host density. Using three different experimental designs, we found a linear functional response by two insect parasitoids (the pteromalid Pachycrepoideus vindemiae and the diapriid Trichopria drosophilae) to their hosts (the drosophilids Drosophila suzukii and D. melanogaster). A linear function response is considered unusual for insect parasitoids. The first design was a 'fixed time within patch experiment' where individual parasitoids were exposed to a range of host densities for 24 h; the second two designs were a 'variable time functional response' and a 'selective functional response' experiments where individual parasitoids were presented with a range of host patches and allowed to freely select and explore only one patch (variable time) or forage for 24 h (selective). In all experimental designs, the number of hosts parasitized increased linearly until reaching an upper limit. Under the laboratory conditions used, the functional response of P. vindemiae was limited by its egg supply and time (host handling time) whereas T. drosophilae was limited by time only. The linear functional response by both parasitoids likely resulted from a constant attack rate and an incremental foraging strategy where the parasitoids left a poor (low density) host patch or remained in a higher quality host patch when there was successful oviposition and adequate host density.
功能反应描述了捕食者或寄生蜂攻击的猎物或寄主数量与猎物或寄主密度之间的函数关系。通过三种不同的实验设计，我们发现两种昆虫寄生蜂（姬小蜂科的米象金小蜂和广肩小蜂科的果蝇广肩小蜂）对其寄主（果蝇科的铃木氏果蝇和黑腹果蝇）呈现出线性功能反应。对于昆虫寄生蜂而言，线性功能反应被认为是不寻常的。第一种设计是“斑块内固定时间实验”，即让单个寄生蜂暴露于一系列寄主密度下24小时；后两种设计是“可变时间功能反应”和“选择性功能反应”实验，在这些实验中，给单个寄生蜂提供一系列寄主斑块，让它们自由选择并仅探索一个斑块（可变时间）或觅食24小时（选择性）。在所有实验设计中，被寄生的寄主数量呈线性增加，直至达到上限。在所使用的实验室条件下，米象金小蜂的功能反应受其卵供应和时间（寄主处理时间）限制，而果蝇广肩小蜂仅受时间限制。两种寄生蜂的线性功能反应可能源于恒定的攻击率和递增的觅食策略，即当成功产卵且寄主密度适当时，寄生蜂会离开质量差（低密度）的寄主斑块或留在质量更高的寄主斑块中。
