Yamawo Akira, Suzuki Nobuhiko, Tagawa Jun
Department of Applied Biological Sciences, Faculty of Agriculture, Saga University, Saga, 840-8502, Japan.
Department of Biosphere-Geosphere System Science, Faculty of Informatics, Okayama University of Science, Okayama, 700-0005, Japan.
J Plant Res. 2019 Jul;132(4):499-507. doi: 10.1007/s10265-019-01119-5. Epub 2019 Jun 21.
Extrafloral nectary (EFN)-bearing plants attract ants to gain protection against herbivores. Some EFN-bearing plants possess different types of EFNs, which might have different effects on ants on the plants. Mallotus japonicus (Thunb.) Muell. Arg. (Euphorbiaceae) bears two types of EFNs, including a pair of large EFNs at the leaf base and many small EFNs along the leaf edge. This study aimed to determine the different roles of the two types of EFNs in biotic defense by ants. A field experiment was conducted to investigate the effect of leaf damage on EFN production and on the distribution pattern of ants. After leaf damage, the number of leaf edge EFNs increased in the leaves first-produced. The number of ants on the leaves also increased, and the foraging area of ants extended from the leaf base to the leaf tip. An EFN-covering field experiment revealed that leaf edge EFNs had a greater effect than leaf base EFNs on ant dispersal on leaves. The extended foraging area of ants resulted in an increase of encounter or attack rate against an experimentally placed herbivore, Spodoptera litura. These results suggest that M. japonicus plants control the foraging area of ants on their leaves using different types of EFNs in response to leaf damage, thus achieving a very effective biotic defense against herbivores by ants.
带有花外蜜腺（EFN）的植物吸引蚂蚁以获得针对食草动物的保护。一些带有EFN的植物拥有不同类型的EFN，这可能对植物上的蚂蚁产生不同影响。野桐（大戟科）有两种类型的EFN，包括叶基部的一对大型EFN和沿叶缘的许多小型EFN。本研究旨在确定这两种类型的EFN在蚂蚁生物防御中的不同作用。进行了一项田间实验，以研究叶片损伤对EFN产生以及蚂蚁分布模式的影响。叶片损伤后，先长出的叶片中叶缘EFN的数量增加。叶片上的蚂蚁数量也增加了，并且蚂蚁的觅食区域从叶基部扩展到叶尖。一项覆盖EFN的田间实验表明，叶缘EFN对蚂蚁在叶片上的扩散的影响比叶基部EFN更大。蚂蚁觅食区域的扩大导致对实验放置的食草动物斜纹夜蛾的遭遇或攻击率增加。这些结果表明，野桐植物通过不同类型的EFN来控制蚂蚁在其叶片上的觅食区域，以应对叶片损伤，从而实现蚂蚁对食草动物非常有效的生物防御。
