Ugine Todd A, Hoki Evan, Losey John E
Department of Entomology, Cornell University, Ithaca, NY.
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA.
Environ Entomol. 2018 Feb 8;47(1):87-92. doi: 10.1093/ee/nvx198.
The importation and establishment of Coccinella septempunctata L. (Coleoptera: Coccinellidae) in North America purportedly caused the displacement and local extirpation of the native ninespotted lady beetle, Coccinella novemnotata Herbst (Coleoptera: Coccinellidae), across most of its former range, and several reports have shown that C. septempunctata maintains competitive advantages over C. novemnotata. We investigated the role of aphid density on the retention time of these two species on fava bean plants, and the effect of con- versus heterospecific pairings of adult beetles on the foraging behavior of C. novemnotata. We found that aphid density did not affect C. novemnotata's retention time, but did affect the retention time of C. septempunctata, which left plants without aphids significantly faster than C. novemnotata. Additionally, C. septempunctata females left plants significantly faster than their male counterparts, whereas we observed no difference between the two sexes for C. novemnotata. Our test of pairs of beetles showed that C. novemnotata were together on plants more frequently than conspecific pairs of C. septempunctata and heterospecific pairs of beetles, and that all beetles were more likely to be found together on the aphid-infested plant versus the non-infested plant regardless of the pairs' composition. These results show that C. novemnotata spend more time foraging for aphids when aphids are scarce compared with C. septempunctata, and that C. novemnotata is less tolerant of occupying plants inhabited by C. septempunctata versus a conspecific beetle, adding additional mechanisms whereby C. septempunctata could outcompete C. novemnotata in the field.
七星瓢虫（鞘翅目：瓢虫科）被引入并在北美定殖，据称这导致了本土的九星瓢虫（赫布斯特九星瓢虫，鞘翅目：瓢虫科）在其大部分原分布范围内被取代并局部灭绝，并且有几份报告表明七星瓢虫相对于九星瓢虫保持着竞争优势。我们研究了蚜虫密度对这两个物种在蚕豆植株上停留时间的影响，以及成年瓢虫的同种配对与异种配对对九星瓢虫觅食行为的影响。我们发现蚜虫密度不影响九星瓢虫的停留时间，但确实影响七星瓢虫的停留时间，七星瓢虫离开没有蚜虫的植株的速度明显快于九星瓢虫。此外，七星瓢虫雌性离开植株的速度明显快于雄性，而我们观察到九星瓢虫两性之间没有差异。我们对瓢虫配对的测试表明，九星瓢虫在植株上一起出现的频率高于七星瓢虫的同种配对和异种瓢虫配对，并且无论配对组成如何，所有瓢虫在有蚜虫的植株上比在无蚜虫的植株上更有可能一起被发现。这些结果表明，与七星瓢虫相比，在蚜虫稀缺时，九星瓢虫会花更多时间觅食蚜虫，并且相对于同种瓢虫，九星瓢虫对占据有七星瓢虫栖息的植株的耐受性更低，这增加了七星瓢虫在野外能够胜过九星瓢虫的额外机制。
