Abstract
The nominal genus Tasactes Faust, 1894, consisting of two originally included nominal species from Myanmar, is rediscovered for the first time since being erected. Adult weevils herein assigned to the taxonomically re-defined Tasactes were abundant in forest floor litter at five localities in China (Yunnan and Sichuan), plus one specimen is available from Shaanxi and three from Nepal. Phylogenetic analysis of a 2,275 bp matrix concatenated from one mitochondrial (COI) and two nuclear markers (ITS2 and 28S) revealed that the monophyletic Tasactes consists of eight evolutionary significant terminal clades, either allopatric (three) or sympatric (two on Cang Shan in Yunnan and three on Mount Emei in Sichuan). The genus Tasactes is nested within the monophyletic Stromboscerini, while the tribe is sister to monophyletic Dryophthorus. The two morphological diagnostic characters of Tasactes, which are unique within the tribe, are the transversely truncated antennal club and conically projecting velvety apex of the club. So defined, Tasactes renders the genus Orthosinus paraphyletic. Considering the taxonomic neglect and uncertainties surrounding nominal Stromboscerini, all herein reported members of this tribe, including the Tasactes, are not assigned to Linnaean species. This paper illustrates the clogging taxonomy phenomenon, in which obscure historical names render taxonomic assignment of newly sampled specimens precarious. All the data used herein (localities, sequences, specimen images) are available online in public datasets dx.doi.org/10.5883/DS-TASACT1 and dx.doi.org/10.5883/DS-TASACT2.
Highlights
This paper was motivated by the discovery of numerous minute and slow-moving Stromboscerini weevils (Fig. 1A) recorded (Figs 1B–E) when forest leaf litter in Southwest China and nearby areas was sifted (Fig. 5 and Supplementary Table S1)
It became evident that any research on the numerous newly sampled Stromboscerini would be haunted by the phenomenon of “clogging taxonomy” (Grebennikov, 2016), in which poorly understood historical names render the usage of the Linnaean nomenclature very unreliable
All 36 Stromboscerini terminals are grouped in 14 ESTC, each with high bootstrap support (99–100%); eight of these clades (D–K in Fig. 3, in red) form the monophyletic Tasactes with bootstrap support of 89%
Summary
This paper was motivated by the discovery of numerous minute and slow-moving Stromboscerini weevils (Fig. 1A) recorded (Figs 1B–E) when forest leaf litter in Southwest China and nearby areas was sifted (Fig. 5 and Supplementary Table S1). The nominal tribe lacks an underlying phylogenetic hypothesis and is likely to be multiply non-monophyletic (Grebennikov, 2018). The type genus from Madagascar was thought to be unrelated to the rest of the tribe distributed mainly in Southeast Asia (Grebennikov, 2018), potentially leaving all but the type genus without a tribal assignment. Doubts remain about the monophyly of all non-monotypic Recent Stromboscerini genera. The widely accepted and century old synonymy of the type species of the genus Xerodermus is doubted (Grebennikov, 2018), which threatens the taxonomic identity of the genus. It became evident that any research on the numerous newly sampled Stromboscerini would be haunted by the phenomenon of “clogging taxonomy” (Grebennikov, 2016), in which poorly understood historical names render the usage of the Linnaean nomenclature very unreliable
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