Listroderini

Oberprieler, Rolf G., 2010, A reclassification of the weevil subfamily Cyclominae (Coleoptera: Curculionidae), Zootaxa 2515, pp. 1-35 : 16-17

Tribe Listroderini LeConte

Listroderini LeConte, 1876: 124 . Palaechtini Brinck, 1948: 43.

This predominantly South American tribe is reasonably well studied, having been subjected to modern revisions (e.g., Morrone 1992, 1994a, 1994b, 1994c, 1994d) as well as phylogenetic ( Morrone 1993b, 1994a, 1997b, Morrone & Anderson 1995) and biogeographical analyses (Morrone 1994e, Morrone & Urtubey 1997, Donato et al. 2003). Alonso-Zarazaga & Lyal (1999) enumerated 30 genera in it, although Morrone (1997b) considered the tribe to also contain genera in New Zealand and Australia (after Kuschel 1964, May 1994), yet without clarifying the limits of the group. Donato et al. (2003) considered Listroderini to be a monophyletic group but were similarly vague about its limits or definition, and their dispersal-vicariance analysis of the 25 American genera also assumed these to constitute a monophyletic grouping despite Morrone’s (1997b) assessment that this was likely to be a paraphyletic assemblage without the five genera from the Tristan da Cunha islands and also the New Zealand and Australian genera. Even within America, however, the composition of the tribe remains unclear.

Rhigopsidius Heller , originally classified in Rhythirrininae ( Heller 1906), was later transferred to Entiminae ( Kuschel 1955, as Leptopiinae ) but reinstated in Rhythirrinini by Wibmer & O’Brien (1986), as the only New-World genus of this tribe and without explanation. This placement was accepted by Morrone & Loiácono (1992) and Morrone (1997b), the latter consequently using Rhigopsidius as outgroup to root his phylogeny of Listroderini . Louw (1998) instead included the genus in his subtribe Gronopina, again without explanation but evidently based on the structure of its ovipositor as described and illustrated by Morrone & Loiácono (1992). However, this ovipositor does not conform to the “clawed type ” as characteristic of Hipporhinini (see above), in that the sharp, outwardly pointed apices of the gonocoxites are not formed by the styli but by the gonocoxites themselves, the styli instead being reduced to a few setae mesally at the base of the bent gonocoxite apices ( Fig. 30). Furthermore, the ovipositor is not as short and broad as it is in Hipporhinini, and the proximal gonocoxites are not laterally extended anteriad. In fact, the ovipositor of Rhigopsidius is rather similar to that of typical Listroderes (the L. costirostris group, after Morrone 1993a, 1993b) ( Fig. 31), and Rhigopsidius evidently belongs near this genus in Listroderini , where it appears more strongly adapted and specialised to a terricolous life and oviposition in soil near potatoes, its larval host. Loiácono & Morrone (1991) regarded its larva to be similar to those of Listronotus Jekel and the New Zealand Nestrius , and Marvaldi (1998) also did not note any larval characters noticeably different from those of other South American Listroderini .

On the other hand, Telurus Kuschel , nested within the Falklandius group of Listroderini in Morrone’s & Anderson’s (1995) cladogram, bears small but clear scars of deciduous cusps on its mandibles ( Figs. 32–33 ), in the same low position where they occur in the entimine tribe Cylydrorhinini , which is also diverse in temperate South America and with which the Listroderini have been affiliated and confused in the past. Atypically of Entiminae , Cylydrorhinini have phanerognathous mouthparts but may, in addition to their mandibular cusps, be distinguished from Listroderini by their dorsally and posteriorly open scrobes. Telurus agrees with Cylydrorhinini also in its mouthparts and scrobes, and its ovipositor is similar to that of Cylydrorhinus Guérin-Méneville in having sharply pointed distal gonocoxites, with the stylus reduced to a subterminal tuft of setae. It therefore belongs in this entimine tribe rather than in Listroderini and Cyclominae . Kuschel (1955) had in fact originally described Telurus in Cylydrorhinini and he only later transferred the genus to Listroderini ( Kuschel 1958) . Whether other genera of the Falklandius group or of Listroderini as currently constituted may be similarly misplaced in this tribe remains to be investigated; species examined of Falklandius Enderlein and of Adioristidius Morrone , Amathynetoides Morrone , Antarctobius Fairmaire , Germainiellus Morrone , Hyperoides Marshall , Listroderes Schoenherr , Listronotus Jekel and Trachodema Blanchard do not have mandibular scars but, as shown by the subantarctic entimine tribe Ectemnorhinini ( Kuschel & Chown 1995), the absence (loss) of mandibular cusps is not necessarily evidence that a genus does not belong to the Entiminae . The current composition and definition of Listroderini is therefore in need of reassessment.

This state of affairs also extends to Australia and New Zealand, where certain genera have sometimes been included in Listroderini but never on the basis of any proper and comprehensive concept of the tribe. Of the Australian “rhythirrinine” fauna (as in Zimmerman 1992), the genera referable to Listroderini are Anorthorhinus , Steriphus and also Methypora (listed in Aterpinae in Zimmerman (1992, 1994)), which differ from the other five genera (here provisionally kept in Rhythirrinini, as above) in possessing tibial spurs (respectively 1-1-1, 1-1-1 or 0-0-0, 0-1-2), a plesiomorphic ovipositor (with small, blunt subapical styli) and also a vestiture similar to that of the South American Listroderini . Also the New Zealand genera Gromilus and Nestrius (again with spur formula 1-1-1) and seemingly Liparogetus (not examined) have to be classified in Listroderini .

No native listroderines are hitherto recorded from Africa, but there are two species of an evidently undescribed genus in the Cape Province of South Africa that must be referred to Listroderini on account of their Steriphus -like habitus and vestiture, tibial spur formula (1-1-2) and unmodified ovipositor. They do not appear to be adventive in South Africa from either South America (as is Hyperoides fragariae Marshall ) or from Australia (no such species described there as Steriphus or Desiantha ) and thus seemingly are the only autochthonous listroderine element in Africa. One of the species has been reared from stems of Geranium (Geraniaceae) and the other collected on leaves of Crassula coccinea (Crassulaceae) . The Gondwanan distribution of Listroderini is further manifested by the discovery of Pliocene fossils in Antarctica ( Ashworth et al. 1997, Ashworth & Kuschel 2003), which were assigned to the Listroderes complex (rather than the Falklandius group), although the head as illustrated in Ashworth & Kuschel (2003) shows weak, dorsolaterally open scrobes more similar to the condition in the Falklandius group.

Given the uncertain composition of Listroderini , no clear definition and diagnosis of the tribe can as yet be provided. Based on the Australian, New Zealand and African genera here assigned to it and a small representation of American genera as examined, the following features characterise the group: dorsum mostly densely setose or squamose, setae on rostrum and pronotum often directed anteriad or mesad, on elytra posteriad; scrobes lateral but posteriorly sometimes curving onto rostral venter, posteriorly mostly open but occasionally angled down (e.g., Listronotus ); epistome generally poorly demarcated, rarely raised ( Acrostomus , Rhigopsidius ); eyes large, flat, usually oval (subcircular in Falklandius and Lanteriella ); mandibles paucisetose (3 or fewer setae); funicles with 1st and often 2nd segment elongated; prothorax with or without ocular lobes; prosternum long, sometimes slightly depressed, rarely excavate ( Rhigopsidius ); tibiae mucronate, generally with 1 or 2 spurs; claws divaricate, simple or with slight basal swelling; gonocoxites generally simple, with large, apical or subapical stylus carrying a tuft of setae, but occasionally without stylus and apex of gonocoxite flattened and bent ( Figs. 30–31).

Information on the biology and hosts of Listroderini is also scarce but more comprehensive than for the other tribes of Cyclominae , largely due to the fact that many listroderine larvae are considered pests in countries where they have been introduced. Suitable summaries with references are given by Marvaldi (1998) for the American and by May (1993, 1994) for the New Zealand and Australian genera.

Figures

FIGURES 32 – 33. Scars of deciduous mandibular cusps of Telurus caudiculatus Morrone & Anderson (Argentina, Ushuaia, Ghiacciaio S. Martial, 22 - 1 - 1988). 32 — front of rostrum in anterior view with mandibles showing ventral scars (arrowed); 33 — mandibular scars enlarged (arrowed).