Integrative taxonomy of the leaf-beetle genus Gonioctena Chevrolat, 1836 in Taiwan (Coleoptera, Chrysomelidae, Chrysomelinae, Gonioctenini) reveals new synonymies and one new species

Taiwanese species of Gonioctena are revised based on morphological, molecular, and ecological information. Gonioctena subgeminata (Chen, 1934), G. tredecimmaculata (Jacoby, 1888), G. kamikawai (Chûjô, 1958), and G. osawai Kimoto, 1996 are redescribed. The study confirms that Phytodecta tredecimmaculatus var. taiwanensis Achard, 1924 should be considered a junior synonym of G. tredecimmaculata (Jacoby, 1888), along with two new junior synonyms, G. ohmomoi Cho et al. 2016 (syn. nov.) and G. riyuetanensis Cho et al. 2016 (syn. nov.). Phytodecta (Asiphytodecta) issikii Chûjô, 1958 (syn. nov.) is treated as a junior synonym of Gonioctena scutellaris Baly, 1862, which is removed from synonym with G. fulva (Motschulsky, 1861) (stat. rev.) and redescribed. Gonioctena thoracica Baly, 1862 (syn. nov.), G. dichroa Fairmaire, 1888 (syn. nov.), and G. foochowensis Gruev, 1989 (syn. nov.) are proposed as junior synonyms of G. scutellaris Baly, 1862. A new species, G. liui sp. nov., is described and differentiated ecologically from G. scutellaris. Gonioctena nigroplagiata Baly, 1862 is newly recorded from Matsu Islands and redescribed. Host plants and biological information are provided for all Taiwanese species. Lectotypes are designated for G. scutellaris Baly, 1862, G. thoracica Baly, 1862, and G. nigroplagata Baly, 1862.