Systematics of the thread-legged bug genus <i>Gardena</i> (Hemiptera: Reduviidae: Emesinae) in East Asia: species delimitation, molecular phylogenetics, and evolutionary implications

Abstract The thread-legged bug genus Gardena Dohrn, 1860 (Hemiptera: Reduviidae: Emesinae) is a cosmopolitan group of about 50 species divided into 4 species-groups. Nine of these species are almost exclusively endemic to East Asia, but their taxonomy has not been fully resolved, and their phylogeny and evolution remain unexplored. In the present study, we conduct a systematic revision of Gardena in East Asia by combining morphological evidence with different molecular species delimitation methods, resulting in the recognition of 3 new species (G. elongata Chen, Li &amp; Cai, sp. n.; G. maizuqii Chen, Li &amp; Cai, sp. n.; and G. tricolor Chen, Li &amp; Cai, sp. n.), the resurrection of a previously synonymized species (G. fusca Fukui, 1926 stat. rev.), and the proposal of 2 new synonymies (G. brevicollis Stål, 1871 = G. albiannulata Ishikawa, 2005 syn. n.; G. melinarthrum Dohrn, 1860 = G. bicolor Distant, 1903 syn. n.). Molecular phylogenetic analyses recover a monophyletic Gardena and reciprocally monophyletic New World and Old World clades, but reject the previous delimitation of the brevicollis and melinarthrum groups. Molecular dating analysis suggests that Gardena likely originated in the early Eocene and then split into the New World and Old World clades in the early Oligocene. During the mid Miocene to mid Pliocene, climatic changes, the uplift of the Himalayas and the Qinghai-Tibet Plateau, and the development of the Asian monsoon system might have driven several dispersal and vicariance events of Gardena in East Asia, leading to most of the divergence events.