The subtribes and genera of the tribe Listroderini (Coleoptera, Curculionidae, Cyclominae): Phylogenetic analysis with systematic and biogeographical accounts

Abstract The phylogenetic relationships of the genera of Listroderini LeConte, 1876 are analyzed based on 58 morphological characters. The genera are grouped in four clades, which are given subtribal status: Macrostyphlina new subtribe (Adioristidius, Amathynetoides, Andesianellus, Macrostyphlus, Nacodius and Puranius), Palaechthina Brinck, 1948 (Anorthorhinus, Gunodes, Haversiella, Inaccodes, Listronotus, Neopachytychius, Palaechthus, Palaechtodes, Steriphus and Tristanodes), Falklandiina new subtribe (Falklandiellus, Falklandiopsis, Falklandius, Gromilus, Lanteriella, Liparogetus, Nestrius and Telurus), and Listroderina (Acroriellus, Acrorius, Acrostomus, Antarctobius, Germainiellus, Hyperoides, Lamiarhinus, Listroderes, Methypora, Philippius, Rupanius and Trachodema). The subtribes are characterized and keys to identify them and their genera are provided. Listroderini have four main biogeographical patterns: Andean (Macrostyphlina), Andean-New Zealand (Falklandiina), Andean-Neotropical-Australian (Listroderina) and Andean-Neotropical-Australian-New Zealand-Nearctic-Tristan da Cunha-Gough islands (Palaechthina). Geographical paralogy, particularly evident in the Subantarctic subregion of the Andean region, suggests that Listroderini are an ancient Gondwanic group, in which several extinction events might have obscured relationships among the areas.


Phylogenetic Analysis
The analysis of the data matrix (Table I) under equal weights and with different concavity constants led to different cladograms: 100 cladograms under equal weights (Fig. 13); three cladograms with k=3 (Fig. 14); six cladograms with k= 6 (Fig. 15); and two cladograms with k= 12 (Fig. 16). In all the analyses the tribe Listroderini is recovered as a monophyletic taxon. Rhigopsidius, previously placed by Oberprieler (2010) in Listroderini, resulted to be the sister taxon to Rhythirrinus (Rhythirrinini). Telurus, excluded from Listroderini by Oberprieler (2010), was placed within Listroderini. In the analyses with k=3 and 6, Aphela (Notiomimetini) is the sister taxon to Listroderini. In spite of the different results, there are some larger clades that were fairly constant.
I consider that the results of the analysis with k= 6 are not as extreme as the others and show more clearly the four main clades, which are treated herein as subtribes ( Fig. 17 Voss, 1954. Diagnosis. Small to very small (1.5-4.1 mm); vestiture consisting of seta-like scales and setae; antennal clubs fusiform; pronotum subcylindrical, disc rugose; metanepisternal sutures posteriorly fused or obliterated; elytral intervals convex.
Relationships. Macrostyphlus is the sister genus of Andesianellus, as hypothesized in a previous analysis (Morrone 1997a).
Biology. Most of the species of Palaechthina are associated to aquatic or semiaquatic plants, being found in wet or damp conditions (May 1970;Morrone and O'Brien 2000). In contrast with the remaining Listroderini, larvae usually lead a more endophytic way of life inside the stems of several aquatic plants (Oberprieler, in press).

Key to the genera of Palaechthina
Relationships. Gunodes is the sister genus to Palaechthus-Paleachtodes-Tristanodes. Oberprieler (1992) considered that the distinction between Gunodes and Tristanodes is not without doubt.

Relationships.
Haversiella is the sister genus to Neopachytychius, and both constitute the sister group to the five genera from the Tristan da Cunha-Gough islands.

Relationships.
Inaccodes is the sister genus to the clade comprising the four remaining genera from the Tristan da Cunha-Gough islands. Oberprieler (1992) considered that the distinction between Inaccodes and Tristanodes is not without doubt.
Relationships. Listronotus is the sister genus to Steriphus (Australia). In a previous analysis based only on American taxa (Morrone 1997a), Listronotus was considered to be the sister genus to Neopachytychius.

Type species. Neopachytychius squamosus
Relationships. Neopachytychius is the sister genus to Haversiella, and both constitute the sister group to the five genera from the Tristan da Cunha-Gough islands. In a previous analysis based only on American genera (Morrone 1997a), Neopachytychius was considered to be the sister genus to Listronotus.
Relationships. Tristanodes is the sister genus to both Palaechthus and Palaechtodes. Oberprieler (1992) considered that the distinction between Tristanodes, Gunodes and Inaccodes is not without doubt.
Relationships. Falklandius is the sister genus to Lanteriella, as found in a previous analysis (Morrone, 1997a).
Relationships. Gromilus is the sister genus to the remaining genera of Falklandiina. Kuschel (1964) already noted the close relationship of Gromilus with Nestrius, Liparogetus and Falklandius.

Type species. Lanteriella microphtalma
Relationships. Lanteriella is the sister genus to Falklandius, as found in a previous analysis (Morrone, 1997a).
Biology. The only species of this genus was hypothesized to live in litter or soil (Morrone 1992b).
Relationships. Telurus is closely related to Falklandius-Lanteriella, as found in a previous analysis (Morrone 1997a), and to Nestrius, from New Zealand. Based on the presence of small scars (due to deciduous cusps) on the mandibles of T. caudiculatus, Oberprieler (2010) excluded the genus from Listroderini and transferred it to Cylydrorhininae (Entiminae). Future molecular analyses are required to corroborate its precise placement.

Key to the genera of Listroderina
Relationships. Acroriellus is the sister genus to Acrostomus-Hyperoides. Originally, it was suggested that it was close to Acrorius (Morrone and Ocampo 1995).
Relationships. Acrorius is the sister genus to Trachodema-Lamiarhinus-Philippius, taxa that in a previous analysis (Morrone 1997a) constituted a paraphyletic group.
Relationships. Antarctobius is closely related to Germainiellus, Listroderes and the clade Methypora-Rupanius-Acrorius-Trachodema-Lamiarhinus-Philippius. The distinction between Antarctobius, Germainiellus and Listroderes is not without doubt (see Morrone and Marvaldi, 1998), and future analyses may determine if they are merged into a single genus.
Relationships. Germainiellus is closely related to Antarctobius, Listroderes and the clade Methypora-Rupanius-Acrorius-Trachodema-Lamiarhinus-Philippius. It was originally described as intermediate between Antarctobius and Listroderes (Morrone, 1993a). The distinction between Antarctobius, Germainiellus and Listroderes is not without doubt (see Morrone and Marvaldi, 1998), and future analyses may determine if they are merged into a single genus.
Relationships. Hyperoides is the sister genus to Acrostomus, contrasting with its more isolated position in a previous analysis (Morrone, 1997a).

Type species. Lamiarhinus aelficus
Relationships. Lamiarhinus is the sister genus to Philippius. In a previous analysis (Morrone 1997a), it was considered to be related to Trachodema.
Relationships. Listroderes is closely related to Antarctobius, Germainiellus and the clade Methypora-Rupanius-Acrorius-Trachodema-Lamiarhinus-Philippius. The distinction between Antarctobius, Germainiellus and Listroderes is not without doubt (see Morrone and Marvaldi 1998), and future analyses may determine if they are merged into a single genus.

Biogeographical Account
The geographical distribution of the genera analysed indicates that Listroderini are basically a Gondwanan taxon, with Listronotus being the only genus distributed in North America. All the subtribes have Andean representatives (especially in the Subantarctic subregion), each showing a different pattern: By replacing the genera for the areas where they are distributed, a taxon-area cladogram was obtained (Fig. 36). The paralogy-free subtrees that can be obtained from this taxon-area cladogram are mostly uninformative, and the informative ones cannot be combined into a general area cladogram. Geographical paralogy is particularly evident in the Subantarctic subregion, where representatives of the four subtribes are represented, suggesting that Listroderini are an ancient Gondwanan group. Several extinction events might have obscured the relationships among the areas.