Roeder Karl A, Prather Rebecca M, Paraskevopoulos Anna W, Roeder Diane V
Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, IL.
Department of Biology, University of Oklahoma, Norman, OK.
Environ Entomol. 2020 Apr 14;49(2):304-311. doi: 10.1093/ee/nvaa016.
For social organisms, foraging is often a complicated behavior where tasks are divided among numerous individuals. Here, we ask how one species, the red imported fire ant (Solenopsis invicta Buren) (Hymenoptera: Formicidae), collectively manages this behavior. We tested the Diminishing Returns Hypothesis, which posits that for social insects 1) foraging investment levels increase until diminishing gains result in a decelerating slope of return and 2) the level of investment is a function of the size of the collective group. We compared how different metrics of foraging (e.g., number of foragers, mass of foragers, and body size of foragers) are correlated and how these metrics change over time. We then tested the prediction that as fire ant colonies increase in size, both discovery time and the inflection point (i.e., the time point where colonial investment toward resources slows) should decrease while a colony's maximum foraging mass should increase. In congruence with our predictions, we found that fire ants recruited en masse toward baits, allocating 486 workers and 148 mg of biomass, on average, after 60 min: amounts that were not different 30 min prior. There was incredible variation across colonies with discovery time, the inflection point, and the maximum biomass of foragers all being significantly correlated with colony size. We suggest that biomass is a solid indicator of how social taxa invest their workforce toward resources and hypothesize ways that invasive fire ants are able to leverage their enormous workforce to dominate novel ecosystems by comparing their foraging and colony mass with co-occurring native species.
对于社会性生物而言，觅食往往是一种复杂的行为，任务由众多个体分担。在此，我们探究一种物种——红火蚁（Solenopsis invicta Buren）（膜翅目：蚁科）是如何集体管理这种行为的。我们测试了收益递减假说，该假说认为对于社会性昆虫来说：1）觅食投资水平会不断增加，直到收益递减导致回报斜率减缓；2）投资水平是群体规模的函数。我们比较了不同觅食指标（例如觅食者数量、觅食者质量和觅食者体型）之间的相关性，以及这些指标随时间的变化情况。然后，我们测试了以下预测：随着火蚁蚁群规模的增加，发现时间和拐点（即蚁群对资源的投资放缓的时间点）都应减少，而蚁群的最大觅食量应增加。与我们的预测一致，我们发现火蚁会大量聚集到诱饵处，60分钟后平均分配486只工蚁和148毫克生物量：这一数量与30分钟前并无差异。不同蚁群在发现时间、拐点以及觅食者的最大生物量方面存在惊人的差异，所有这些都与蚁群规模显著相关。我们认为生物量是社会性类群如何将其劳动力投入资源的可靠指标，并通过比较入侵火蚁与同时存在的本地物种的觅食和蚁群规模，推测入侵火蚁能够利用其庞大的劳动力主导新生态系统的方式。
