Nanoplaxes

Tang, William, Xu, Guang, Marler, Thomas, Khuraijam, Jibankumar Singh, Singh, Rita, Lindström, Anders J., Radha, P., Rich, Stephen, Nguyen, Khang Sinh & Skelley, Paul, 2020, Beetles (Coleoptera) in cones of cycads (Cycadales) of the northern hemisphere: diversity and evolution, Insecta Mundi 2020 (781), pp. 1-19 : 4

Nanoplaxes weevil group

A maximum likelihood tree for the Asian cycad weevils ( Nanoplaxes group) generated from molecular data is published here for the first time ( Fig. 2 ). In previous assessments of this group, these weevils were tentatively assigned to the genus Tychiodes Wollaston ( Oberprieler 1995; Tang et al. 1999). The genus Tychiodes was originally described from “Awasima Island off the northwest coast of Nipon” ( Wollaston 1873), a locality today that most closely corresponds to the island of Awashima off the northwest coast of Shikoku, one of the four main islands of Japan. Awashima is 270 km northeast of the northernmost population of Cycas revoluta Thunb. ( Osborne and Tomiyama 1995) , the only cycad native to Japan. A detailed survey of the Coleoptera inhabiting C. revoluta in Yomaguni Island (Okinawa, Japan) revealed no Tychiodes beetles (Kono and Tobe 2001), therefore we can confidently assume that the type species for Tychiodes does not use Cycas as a host and likely does not belong in this clade, although it may be related. Here we use the genus Nanoplaxes , described from specimens collected in Pegu, India (now Myanmar) and Luzon, Philippines ( Heller 1913), to represent this clade. Examination of the type specimens of Nanoplaxes , located in Dresden, by the senior author indicates a close match with specimens collected recently in Thailand and Vietnam on Cycas cones. Tang et al. (1999) divided this group tentatively into three clades: A) Group A corresponds with the genus Nanoplaxes , a group of relatively large, dorso-ventrally compressed weevils ( Fig. 2 ); B) Group B consists of a group of smaller weevils, with more cylindrical shape ( Fig. 2 ); in this analysis group B does not form a monophyletic lineage, but rather four distinct clades, some which are sister either to Nanoplaxes or Group C, but not both simultaneously; C) Group C consists of morphologically distinctive, narrowed-bodied weevils with long snouts; this analysis supports Group C as being monophyletic ( Fig. 2 ); D) Specimens matching Tychiosoma Wollaston appear in our tree as the sister lineage to these other groups in this analysis ( Fig. 2 ). Overall the Nanoplaxes weevil group is well supported as a natural, monophyletic clade in this analysis (bootstrap support = 94). Oberprieler (1995) reluctantly retained this group of weevils within the subfamily Cossoninae while indicating a possible placement in Curculioninae : Molytini . Tang et al. (1999) placed it in Molytinae : Trypetidini . In this analysis the Nanoplaxes complex does not sort with species of Cossoninae , Dryophthorinae , Entiminae , Hyperinae , or Apioninae used as outgroups, but may be closer to Cryptorhynchinae. A recent phylogeny of Curculionidae by McKenna et al. (2009), based on a multi-gene sample, places the Trypetidini near Ceutorhynchini . In their tree, however, Cossoninae , Curculioninae , and Molytinae all appear polyphyletic, suggesting that many of the morphological characters that tie members of these subfamilies together are the result of convergent morphological evolution and that much of the subfamilial and tribal taxonomy of the family Curculionidae requires reassessment.

Figures

Figure 2. Phylogenetic tree for Asian weevils of the Nanoplaxes group based on maximum likelihood analysis of 16S rRNA mitochondrial gene sequences, scale bar indicates base pair substitution per nucleotides position, numbers on branches are bootstrap values.