One hundred and three new species of Trigonopterus weevils from Sulawesi

Abstract The genus Trigonopterus Fauvel, 1862 is highly diverse in Melanesia, the Moluccas, and the Sunda Islands. Only one species, Trigonopterusfulvicornis (Pascoe, 1885) was so far recorded from Sulawesi. Based on focused field-work the fauna from Sulawesi and nearby islands is here revised. We redescribe T.allotopus Riedel newly recorded for Sulawesi and describe an additional 103 new species: T.abnormissp. n., T.adspersussp. n., T.ambangensissp. n., T.ampanensissp. n., T.analissp. n., T.arachnobassp. n., T.armipessp. n., T.artemissp. n., T.asterixsp. n., T.barbipessp. n., T.bonthainensissp. n., T.carinirostrissp. n., T.castaneipennissp. n., T.celebensissp. n., T.cirripessp. n., T.collarissp. n., T.costatulussp. n., T.curvipessp. n., T.crenulatussp. n., T.crickisp. n., T.darwinisp. n., T.ejaculatoriussp. n., T.fuscipessp. n., T.gracilipessp. n., T.hebertisp. n., T.hirsutussp. n., T.humilissp. n., T.hypocritasp. n., T.idefixsp. n., T.impressicollissp. n., T.incendiumsp. n., T.incognitussp. n., T.indigenussp. n., T.inhonestussp. n., T.invalidussp. n., T.jasminaesp. n., T.klabatensissp. n., T.kolakensissp. n., T.kotamobagensissp. n., T.laevigatussp. n., T.lamprossp. n., T.latipennissp. n., T.lompobattangensissp. n., T.luwukensissp. n., T.mahawuensissp. n., T.manadensissp. n., T.mangkutanensissp. n., T.matalibaruensissp. n., T.mesaisp. n., T.minahassaesp. n., T.moatensissp. n., T.modoindingensissp. n., T.nanussp. n., T.nitidulussp. n., T.obelixsp. n., T.ovalipunctatussp. n., T.ovatulussp. n., T.pagaranganensissp. n., T.palopensissp. n., T.paracollarissp. n., T.paupersp. n., T.pendolensissp. n., T.posoensissp. n., T.prismaesp. n., T.procurtussp. n., T.pseudallotopussp. n., T.pseudanalis, sp. n., T.pseudovatulussp. n., T.pseudovalipunctatussp. n., T.pseudofulvicornissp. n., T.pseudomanadensissp. n., T.pseudosimulanssp. n., T.pumilussp. n., T.rantepaosp. n., T.reticulatussp. n., T.rhombiformissp. n., T.rotundatussp. n., T.rotundulussp. n., T.rudissp. n., T.rufipessp. n., T.sampunensissp. n., T.sampuragensissp. n., T.satyrussp. n., T.scabripessp. n., T.scaphiformissp. n., T.scitulussp. n., T.selayarensissp. n., T.serripessp. n., T.seticnemissp. n., T.silvicolasp. n., T.squalidulussp. n., T.sulawesiensissp. n., T.suturatussp. n., T.tatorensissp. n., T.tenuipessp. n., T.tomohonensissp. n., T.torajasp. n., T.vicinussp. n., T.viduussp. n., T.volcanorumsp. n., T.wangiwangiensissp. n., T.watsonisp. n., and T.yodasp. n. All new species are authored by the taxonomist-in-charge, Alexander Riedel.


Introduction
Trigonopterus Fauvel, a genus of flightless weevils placed in the subfamily Cryptorhynchinae of Curculionidae (Alonso-Zarazaga and Lyal 1999) currently comprises 341 species, herein brought to 444 species. It ranges from Sumatra to Samoa, and from the Philippines to Northern Australia. Its center of origin and presumably its highest diversity is in the Papuan region (Riedel et al. 2013b;Riedel et al. 2014;Tänzler et al. 2012;Tänzler et al. 2016;Toussaint et al. 2017;unpublished data). The Sunda Islands further west harbor a less diverse fauna of Trigonopterus; still, 99 described species have been recorded from Sumatra, Borneo, Java, and the Lesser Sunda Islands . The island of Sulawesi formerly known as "Celebes" is located between these two regions (Lohman et al. 2011;Stelbrink et al. 2012), and a rich fauna can be expected from this geographic position (Whitten et al. 2012). However, only one single species, T. fulvicornis (Pascoe, 1885) has been described from Sulawesi to date (Riedel 2011). Our own field-work soon revealed this pattern as a sampling artefact and numerous undescribed Sulawesi Trigonopterus were included in the phylogeny of Tänzler et al. (2016) [supplement figure S1].
The purpose of the present publication is to make available a substantial number of names of Sulawesi Trigonopterus and to provide a preliminary baseline for their taxonomy. Species of the smaller offshore islands of Selayar and Wangi Wangi are also included.
We follow the previously established approach of accelerated or "fast-track" taxonomy that combines the benefits of molecular and morphological systematics (Riedel et al. 2013a(Riedel et al. , b, 2014. The taxonomic information on the genus is bundled on open access websites, i.e., species-ID (http://species-id.net/wiki/Trigonopterus), respectively wikispecies (https://species.wikimedia.org/wiki/Trigonopterus ).
The phylogenetic relationships of the species are indicated by a provisional catalogue of species groups. The name of one existing subgenus (i.e., Mimidotasia Voss) is being used, but we refrain from describing additional subgenera at this point. Instead, the use of informal species groups appears more adequate, as this system can be adjusted without the restrictions of nomenclature in future. Moreover, there is a lesser demand for reflecting the same hierarchy, i.e., morphologically diverse clades can be subdivided into a greater number of groups while morphologically uniform clades are left undivided.

Materials and methods
This study is based on 3,953 specimens of Trigonopterus, most of them collected specifically for a larger project on this genus. Specimens were collected by tipping foliage over a beating sheet or by sifting the litter of primary forests with subsequent extraction by hand or using eclectors (Besuchet et al. 1987). Holotypes were selected from the 514 sequenced specimens; their DNA had been extracted nondestructively as described by Riedel et al. (2010). The genitalia of most specimens did not require maceration after DNA-extraction; they could be directly stained with an alcoholic Chlorazol Black solution and stored in glycerol in microvials attached to the pin of the specimens. Genitalia of collection specimens or specimens whose abdominal muscle tissue was not sufficiently digested after DNA extraction were macerated with 10% KOH and rinsed in diluted acetic acid before staining. Illustrations of habitus and genitalia were prepared from holotypes. Finally, type series were supplemented with specimens stored in ethanol and older material from the dry collection. As always the case in paratypes, there is a chance that some of these are incorrectly assigned; this is especially true for specimens without sequence data as an identification based on external morphological characters is more prone to error than an identification based on a cox1 sequence (Tänzler et al. 2012). Type depositories are cited using the following abbreviations: limited to major diagnostic characters as outlined by Riedel et al. (2013a, b). Negative character states (i.e., the absence of a character) are only mentioned explicitly where it appears appropriate. In groups comprising hundreds of species enumerating the absence of rare character states leads to inflated descriptions that distract the reader from the important information, i.e., the diagnostic characters present in a given species.
Morphological terminology follows Beutel and Leschen (2005) and Leschen et al. (2009), i.e., the terms "mesoventrite" / "metaventrite" are used instead of "mesosternite" / "metasternite", and "mesanepisternum" / "metanepisternum" instead of "mesepisternum" / "metepisternum"; "penis" is used instead of "aedeagus" as the tegmen is usually without useful characters in Trigonopterus and therefore omitted from species descriptions. Specimens were examined with a Leica MZ16 dissecting microscope and a fluorescent desk lamp for illumination. Measurements were taken with the help of an ocular grid. The length of the body was measured in dorsal aspect from the elytral apex to the front of the pronotum. Legs were described in an idealized laterally extended position; there is a dorsal / ventral and an anterior / posterior surface. Habitus illustrations were compiled using a DFC495 camera with L.A.S. 4.8.0 software adapted to a Z6 APO (all from Leica Microsystems, Heerbrugg, Switzerland). Photographic illustrations of genitalia were made using a DFC450 camera with L.A.S. 4.8.0 software adapted to an Axio Imager M2 microscope (Carl Zeiss Microscopy), with 5×, respectively 10× A-Plan lenses; resulting image stacks were compiled using the Helicon Focus 6.7.1 Pro software (Helicon Soft Ltd). For photography genitalia were temporarily embedded in glycerol gelatin as described by Riedel (2005), with their longitudinal axis somewhat lifted anteriorly, to adequately illustrate structures of the curved down apex. All photographs were enhanced using Adobe Photoshop CS2 and CS6. However, care was taken not to obscure or alter any features of the specimens illustrated. Sequence data were submitted to the European Molecular Biology Laboratory (EMBL), respectively to GenBank of NCBI (National Center for Biotechnology Information) and the accession numbers are provided under each species e.g., as "(EMBL # LN884964)".
Newly identified species are provided with a species number which was consistently used before a scientific name became available, e.g. in phylogenies  or for sequence data entries. To allow later interpretation of such data, these species numbers are given in "Notes". Species groups were defined in a combined approach to agree with monophyletic clades of our molecular phylogenies   fig. S1; unpublished data) and to reflect morphological characters. Since the weevil´s life style on foliage versus edaphic in leaf litter has a great impact on its outer appearance, it was attempted to delineate groups of species with a single life style.
Distribution. SE-Sulawesi Prov. (Kolaka). Elevation ca. 180 m. Biology. In leaf litter of lowland forest. Etymology. This epithet is based on the Latin adjective analis, e (pertaining to the anus) and refers to the peculiar morphology of ventrite 5.

Trigonopterus arachnobas
Etymology. This epithet is based on the genus name Arachnobas Boisduval and is treated as a noun in apposition. It refers to the superficial resemblance of the species´ habitus.
Distribution. N-Sulawesi Prov. (Mt Klabat). Elevation ca. 1030 m. Etymology. This epithet is based on a character of the French Asterix comics. It is a noun in apposition.
Notes. Trigonopterus collaris Riedel, sp. n. was coded as "Trigonopterus sp. 384". This species is closely related to T. paracollaris Riedel, sp. n., from which it can be distinguished by the elytral sculpture and the morphology of the male genitalia.
Etymology. This epithet is based on the diminutive form of the Latin adjective costatus, -a, -um (ribbed) and refers to the species´ small size and its elytral sculpture.
Notes. Trigonopterus costatulus Riedel, sp. n Etymology. This epithet is based on the ductus ejaculatorius which is markedly swollen in males of this species. It is treated as an adjective.
Notes. Trigonopterus ejaculatorius Riedel, sp. n. was coded as "Trigonopterus sp. 507". It is closely related to T. vicinus Riedel, sp. n. from which it differs by 17.3% p-distance of cox1 and can be distinguished by the subangular basal hump of the rostral profile.
Notes. Trigonopterus fuscipes Riedel, sp. n. was coded as "Trigonopterus sp. 526". This species is very closely related to T. asterix Riedel, sp. n., from which it differs by ca. 12% p-distance of cox1 and by the structure of the male genitalia.
Notes. Trigonopterus hirsutus Riedel, sp. n. was coded as "Trigonopterus sp. 485". Most of the specimens examined are females (2 males / 74 females); the reason for this unequal proportion is unknown.
Notes. Trigonopterus impressicollis Riedel, sp. n. was coded as "Trigonopterus sp. 491".  Etymology. This epithet is the Latin noun incendium (burning, arson) in apposition and refers to the type locality Tanjung Api (Cape of Fire) with flames of natural gas.

Trigonopterus indigenus
Etymology. This epithet is the Latin adjective inhonestus, -a, -um (disgraceful) and refers to the name of T. honestus (Pascoe), a sibling species.
Notes. Trigonopterus inhonestus Riedel, sp. n. was coded as "Trigonopterus sp. 946". This species is closely related to T. honestus (Pascoe) which occurs in North Maluku and can be distinguished by a longer flagelliform transfer apparatus of the male genitalia, by a slightly larger body size, and by the absence of scale patches near the elytral base. It is the only member of the T. honestus group currently known from Sulawesi. It occupies a relatively wide range from Mt Rantemario in South Sulawesi to Tomohon in the north. Different populations are genetically structured but appear conspecific.
Notes. Trigonopterus obelix Riedel, sp. n. was coded as "Trigonopterus sp. 376". This species is closely related to T. posoensis Riedel, sp. n., from which it differs by ca. 15.0-15.5% p-distance of cox1, and by the rounded profile of abdominal ventrite 2.
Etymology. This epithet is the diminutive form of the Latin adjective ovatus, -a, -um (egg-shaped) and refers to the species´ body form and small size. It is a variable adjective as well.
Notes. Trigonopterus ovatulus Riedel, sp. n. was coded as "Trigonopterus sp. 535". This species is very closely related to T. pseudovatulus Riedel, sp. n., from which it cannot be separated by morphological characters. It differs by ca. 17.1-17.3% p-distance of cox1, correlated by marked differences in the nuclear genes 28S and CAD. Two allopatric populations occur at Gn. Karre and at the mountains north of Lake Poso. The latter population is sympatric with T. pseudovatulus Riedel, sp. n.. In the future, more comprehensive studies could lead to the conclusion that these populations also constitute distinct species.
Notes. Trigonopterus paracollaris Riedel, sp. n. was coded as "Trigonopterus sp. 528". This species is closely related to T. collaris Riedel, sp. n., from which it can be distinguished by the elytral sculpture and the morphology of the male genitalia.
Notes. Trigonopterus posoensis Riedel, sp. n. was coded as "Trigonopterus sp. 377". This species is very closely related to T. obelix Riedel, sp. n., from which it differs by ca. 15.0-15.5% p-distance of cox1, and by the subangularly projecting profile of abdominal ventrite 2.
Etymology. This epithet is based on the Greek prefix pseudo-(false) and the name of T. allotopus Riedel, a sibling species. A noun in apposition.
Notes. Trigonopterus pseudallotopus Riedel, sp. n. was coded as "Trigonopterus sp. 945". This species is closely related to T. allotopus Riedel, from which it differs by ca. 5.8-6.4% p-distance of cox1 and morphologically by the weakly impressed striae 7-9 of the elytral humeri.
Notes. Trigonopterus pseudanalis Riedel, sp. n. was coded as "Trigonopterus sp. 944". This species is very closely related to T. analis Riedel, sp. n., from which it differs by ca. 11.7-12.7% p-distance of cox1, by the apex of the penis, and by a stouter body shape with a more densely punctate pronotum.
Notes. Trigonopterus pseudovatulus Riedel, sp. n. was coded as "Trigonopterus sp. 534". This species is very closely related to T. ovatulus Riedel, sp. n., from which it cannot be separated by morphological characters. It differs by ca. 17.1-17.3% p-distance of cox1, correlated by marked differences in the nuclear genes 28S and CAD.

Biology. On foliage in lowland forests.
Etymology. This epithet is a Latinized adjective based on the Greek prefix pseudo-(false) and the name of Trigonopterus fulvicornis (Pascoe) which is superficially very similar.
Etymology. This epithet is based on the town of Rantepao, center of the Land of Toraja. It is treated as a noun in apposition.
Notes. Trigonopterus rantepao Riedel, sp. n. was coded as "Trigonopterus sp. 409". It is closely related to T. toraja Riedel, sp. n. from which it can be distinguished by the structure of the penis.
Etymology. This epithet is the Latin participle rotundatus, -a, -um (rounded) and refers to the species´ habitus.
Etymology. This epithet is the Latin adjective rudis, -e (coarse, rough) and refers to the species´ sculpture.
Notes. Trigonopterus rudis Riedel, sp. n. was coded as "Trigonopterus sp. 519". Diagnostic description. Holotype, male (Fig. 85a). Length 3.14 mm. Color of antennae and legs ferruginous; remainder black. Body elongate; in dorsal aspect with distinct constriction between pronotum and elytron; in profile dorsally flat. Rostrum dorsally with median ridge and pair of submedian ridges; intervening furrows with rows of erect subclavate scales; epistome short, with median denticle, laterally with two denticles on the right and with one denticle on the left of rostral apex. Pronotum with disk subquadrate, anteriorly forming angulation, before converging to weak subapical constriction; densely coarsely punctate; interspaces between punctures subglabrous; in anterior 1/2 with erect subclavate scales; median line weakly costate, impunctate. Elytra densely irregularly punctate; along basal margin and humeri with punctation more densely; striae marked by fine hairlines; apex subtruncate; apex and base with sparse scales. Foreleg relatively long. Femora with small acute tooth; anteroventral ridges of meso-and metafemur weakly crenate; anterior surface coarsely punctate, reticulate, each puncture with long subclavate scale. Metafemur subapically with stridulatory patch. Dorsal edge of tibiae serrate. Abdominal ventrites 1-2 concave, microreticulate, with sparse punctures bearing erect elongate scales; ventrite 5 flat, coarsely punctate, with erect scales. Penis (Fig. 85b)   Etymology. This epithet is a combination of the Latin adjective scaber, -a, -um (rough) and the noun pes (foot, leg) and refers to sculpture and vestiture of the species´ legs. It is to be treated as a noun in apposition.

Trigonopterus rufipes
Notes. Trigonopterus scabripes Riedel, sp. n. was coded as "Trigonopterus sp. 493".  Etymology. This epithet is a combination of the Latin nouns scapha (boat, skiff), forma (shape) and the 2 nd adjectival declension ending -is, and refers to the body shape of this species.

Trigonopterus scaphiformis
Notes. Trigonopterus scaphiformis Riedel, sp. n. was coded as "Trigonopterus sp. 497". Biology. In leaf litter of montane forest. Etymology. This epithet is the diminutive form of the Latin adjective squalidus, -a, -um (rough; dirty) and refers to the species´ small size and its rough integument often incrusted with dirt. A variable adjective as well.
Notes. Trigonopterus suturatus Riedel, sp. n. was coded as "Trigonopterus sp. 488". Diagnostic description. Holotype, male (Fig. 104a). Length 2.71 mm. Color of antennae light ferruginous; legs and head dark ferruginous; remainder black with slight bluish luster. Body subovate; in dorsal aspect with distinct constriction between pronotum and elytron; in profile dorsally convex. Rostrum at base markedly bent ventrad; with lateral flanges in front of eyes; dorsally with distinct median carina and pair of submedian ridges; intervening furrows each with row of erect, clavate scales; epistome indistinct. Pronotum laterally with marked subapical constriction; except near base disk coarsely punctate; interspaces subglabrous, reticulate; with subglabrous median ridge. Elytra with striae marked by dense rows of small punctures and weak hairlines; intervals each with a similar row of punctures; interspaces subglabrous; subapically with sparse short setae; apex subtruncate. Femora edentate; anteroventral ridge distinct; anterior surface coarsely punctate, each puncture with subclavate scale. Metafemur dorsally denticulate; subapically with stridulatory patch. Metatibia with dorsal edge denticulate. Abdominal ventrites 1-2 concave, subglabrous, with long erect slightly curved setae; ventrite 5 flat, punctate, microreticulate. Penis (Fig. 104b) with sides of body subparallel; apex with median constriction, with sparse setae; apodemes 2.6 × as long as body of penis; transfer apparatus thick flagelliform, S-shaped, 1.3 × longer than body of penis; ductus ejaculatorius with indistinct bulbus. Intraspecific variation. Length 2.28-2.73 mm. Female rostrum slender, dorsally with ridges less distinct; at base with few erect scales, anteriorly nude. Etymology. This epithet is a noun in apposition based on the fictional character Yoda in George Lucas´ Star Wars movies. It appears to fit to a small greenish forestdwelling creature.

Discussion
Our first study on Papuan Trigonopterus established the approach of accelerated taxonomy combining morphology and DNA barcoding by naming only selected representatives of a highly diverse fauna (Riedel et al. 2013a, b). The subsequent revisions of the Sunda Islands  and Australia ) treated all available species of a region. The present study is a compromise of both strategies. It is based on focused, yet limited field-work in Sulawesi. There are more than 30 additional species at hand, mostly represented by female specimens that should not be formally described unless additional material can be produced. Trigonopterus fulvicornis (Pascoe), the only previously described species from Sulawesi is not among our recent material although we searched near its type locality, Kendari. Vast areas of Sulawesi have never been sampled for small beetles and our current geographic sampling for Trigonopterus thus remains patchy. Many additional species are to be expected with the survey of additional localities in a group that is known for local endemism (Tänzler et al. 2012). Thus, the present work is only a first step and the species total of Sulawesi Trigonopterus is likely to double with additional surveys. As a consequence, an identification key based on morphological characters is useless at this stage because a high proportion of species are still missing. Another complicating factor is the scarceness of distinct morphological characters that remain stable over major groups; instead characters abound that are diagnostic of species or small groups of species, but disappear among larger species groups. In this situation, BLAST searches for cox1 sequences can give a much better indication if a species is contained in published datasets than a traditional key. Absolute values of sequence divergence warranting species status cannot be provided, nor is a definition of thresholds the subject of this paper. However, based on our experience, an uncorrected cox1 p-distance of less than ca. 5% is a first indication that two Trigonopterus specimens are conspecific and such a result may be seen as a preliminary identification, especially if genital and other morphological characters confirm this; hits with distances around 10% may point to separate, although related species, while distances exceeding 15% approach a saturation of sequence information and the phylogenetic relationship of a species as resolved by cox1 becomes increasingly uncertain. Thus, the extent of sequence divergence gives clues on the further procedure, ranging from a final identification (after morphological comparison of two closely related specimens) to the sequencing of additional markers to resolve the phylogenetic position of a new, divergent lineage.
Sulawesi is located at the heart of Wallacea, a transient zone between the Oriental and Australian faunas and thus of great interest to biogeographers (Lohman et al. 2011). Some Trigonopterus species were already cited in the datasets of Tänzler et al. (2014Tänzler et al. ( , 2016 with manuscript species numbers. A more detailed study on the biogeography of Sulawesi Trigonopterus is in preparation and herein we provide names and faces to more than one hundred new species that will be part of the dataset. An approach providing valid names and highresolution digital images is surely more sustainable than the extended use of morphospecies numbers without descriptions. Sometimes there is a prolonged lag between the publication of biogeographic (and other) research data and the taxonomic information that should provide their base. Too much perfectionism on the taxonomists´ side may raise doubts on their ability to provide their service to other fields of research. Names should become available as soon as possible and not be postponed for ever awaiting a better sample size.
There is also an urgent need for conservation measures and it is hoped that this is highlighted by the availability of species names. Most species of Sulawesi Trigonopterus are reported from the type locality only (79 species). A smaller number are from two or more localities with a linear distance of 12-30 km (15 species), or 50-90 km (8 species). Presumably, the average range of a Trigonopterus species in Sulawesi measures less than 100 km. The status of two populations of T. ovatulus Riedel, sp. n. separated by 160 km is uncertain and both may represent distinct species. There remain two notable species: 1) T. allotopus Riedel, previously described from Sumbawa Island, is herein recorded from SE Sulawesi near Kolaka and to date the only species of Sulawesi Trigonopterus also found on another island; this appears to be a case of relatively recent dispersal between two islands. 2) T. inhonestus Riedel, sp. n., spanning a linear distance of 780 km and ranging over at least three provinces of Sulawesi; this species is also exceptional in its capability of surviving in somewhat degraded habitats.
Thus, most of the Trigonopterus species recorded herein are endemic to the island of Sulawesi (with one exception) and most of them appear to occupy ranges of less than 100 km linear distance (three exceptions). With their high endemism, they are also highly endangered by habitat loss. Being flightless and ecologically tied to primary forest they are more vulnerable than many vertebrates or butterflies that may be able to colonize and re-colonize habitats of a wider distribution range. A flightless endemic weevil will vanish with its surrounding forest. Of Sulawesi´s natural forests only 30% are left in good condition, and these limited areas are now under increasing pressure, especially lowland forests (Cannon et. al. 2007). If we look at some of the areas where many of the newly described species have been discovered, the suitable habitats are much reduced and usually without effective protection. For example, at Mt Lompobattang, a hotspot of endemic arthropods, the natural forest below 1.700 m has been replaced by vegetable gardens. In densely populated Tanah Toraja natural forests are restricted to a few remaining areas: reforestation for timber usually leads to pine plantations that are unsuitable habitats for most of the native species. At Mt Mahawu near Tomohon natural forest has almost disappeared within the past 20 years. In fact, all these refugia may be already too small to be gazetted as National Parks or reserves with effective conservation measures, but still they contain (or used to contain) a unique and diverse fauna as exemplified by the newly described Trigonopterus weevils. A single forest fire during the dry season may seal the fate of many endemic species of Mt Klabat or Mt Lompobattang. The recent popularity of mountaineering increases the risk of camp fires getting out of control. Clearly, the majority of the largely endemic Trigonopterus species of Sulawesi cannot be preserved for the future unless the conservation of isolated remnants of natural forests can be greatly improved.
The Trigonopterus fauna of Sulawesi as currently known is composed of only few major phylogenetic lineages (figure S1 of Tänzler et al. 2016; unpublished data): 1) four species of the subgenus Mimidotasia Voss; 2) two species of the T. politus-group; 3) three species of the T. curtus-group; 4) one species of the T. honestus-group; and 5) the remainder of all Sulawesi and Sunda species combined forming the "clade G" of Tänzler et al. (2016). This latter clade is speciose and morphologically heterogeneous. Its 180 described species comprise groups of both edaphic and foliage-frequenting lifestyles. They are herein subdivided into 28 separate species groups, owing to a lack of morphological characters that would allow the delineation of larger groups. Thus, based on morphological characters alone, the Trigonopterus fauna of Sulawesi appears more heterogeneous than it actually is. It is hoped that the present study encourages additional field work in the area. A higher sampling density would surely allow a better view on what may be one of the largest radiations on the island of Sulawesi. Riedel, sp. n., T. pseudovatulus Riedel, sp. n. T. palopensis-group: T. asterix Riedel, sp. n., T. fuscipes Riedel, sp. n., T. kotamobagensis Riedel, sp. n., T. latipennis Riedel, sp. n., T. matalibaruensis Riedel, sp. n., T. moatensis Riedel, sp. n., T. palopensis Riedel, sp. n., T. rhombiformis Riedel, sp. n