A novel host shift and invaded range of a seed predator, Acanthoscelides macrophthalmus (Coleoptera: Chrysomelidae: Bruchinae), of an invasive weed, Leucaena leucocephala

An endophagous seed predator, Acanthoscelides macrophthalmus (Coleoptera: Chrysomelidae: Bruchinae),
utilizes Neotropical Leucaena (Fabaceae: Mimosoideae). One of its hosts, Leucaena leucocephala, is a
fast-growing nitrogen-fixing tree that serves as a multipurpose beneficial plant but eventually becomes an
aggressive invader where it was introduced. Herein, we report A. macrophthalmus invasion of the Far East,
South Asian tropics and subtropics (Japanese Pacific Islands, Taiwan, Southern China, Northern Thailand
and Southern India). Of other field-collected mimosoid legumes, an introduced tree, Falcataria moluccana,
in Taiwan was found to be used by the seed predator. Conversely, our published work review revealed that
the seed predator had retained high host specificity to Leucaena species in its native and introduced regions.
Acanthoscelides macrophthalmus was able to utilize aphagously postharvest mature seeds for oviposition
and larval development, which is a trait of post-dispersal seed predators.We confirmed that A. macrophthalmus
that was reared on L. leucocephala was able to utilize F. moluccana as well. Although the relatively high
host specificity of the oligophagous beetle is suitable for controlling the weedy L. leucocephala, the potential
host range expansion confirmed by this study must be cautioned.

一种内食性种子捕食者——阔脸豆象（Acanthoscelides macrophthalmus，鞘翅目（Coleoptera）、叶甲科（Chrysomelidae）、豆象亚科（Bruchinae）），其寄主为新热带区银合欢属（Leucaena）植物，该属隶属于豆科（Fabaceae）含羞草亚科（Mimosoideae）。其寄主之一银合欢（Leucaena leucocephala）为速生固氮树种，兼具多用途益用价值，但在引种区域最终演变为恶性入侵物种。本文报道了该豆象入侵远东、南亚热带及亚热带区域（日本太平洋列岛、中国台湾、中国南方、泰国北部及印度南部）的情况。在野外采集的其他含羞草亚科豆科植物中，中国台湾的引种树种南洋楹（Falcataria moluccana）被发现可被该种子捕食者利用。反之，我们的已发表研究综述显示，该种子捕食者在原生境与入侵区域均对银合欢属物种保持较高的寄主专一性。阔脸豆象可利用无取食行为的收获后成熟种子完成产卵与幼虫发育，这一特性符合扩散后种子捕食者的类群特征。我们证实了以银合欢繁育的阔脸豆象同样可利用南洋楹。尽管这种寡食性甲虫较高的寄主专一性可用于防控入侵性银合欢，但本研究证实的潜在寄主范围扩张风险仍需引起警惕。