Seven new species of Trigonopterus Fauvel (Coleoptera, Curculionidae) from the Tanimbar Archipelago

Abstract Based on recent fieldwork, the hyperdiverse weevil genus Trigonopterus Fauvel is recorded for the first time from the Indonesian Tanimbar Archipelago, halfway between Australia and Western New Guinea. All seven species discovered on Tanimbar are new to science, and described here: Trigonopterus atufsp. nov., T. kumbangsp. nov., T. laratensissp. nov., T. porgsp. nov., T. selaruensissp. nov., T. tanimbarensissp. nov., and T. triradiatussp. nov. The new species are authored by the taxonomists-in-charge, Raden Pramesa Narakusumo and Alexander Riedel. This fauna appears discordant and established by relatively recent dispersal from New Guinea and other Moluccan islands.


Introduction
Trigonopterus Fauvel is a genus of hidden snout weevils (Cryptorhynchinae) (Alonso-Zarazaga and Lyal 1999; . These beetles are flightless, yet the 444 species currently known cover a large geographic area, across the Indo-Australian Ar-chipelago and into Oceania (Riedel et al. 2010(Riedel et al. , 2014van Dam et al. 2016). Hundreds of additional species await discovery (Riedel et al. 2013b(Riedel et al. , 2014Riedel and Narakusumo 2019; https://species-id.net/ wiki/Trigonopterus; unpublished data). New Guinea is the center of Trigonopterus diversity (Tänzler et al. 2012(Tänzler et al. , 2017. The relatively rich Trigonopterus faunas of Sulawesi and Sundaland originated by dispersal from New Guinea and subsequent diversification . The fauna of the Moluccan Islands may have served as stepping stones, yet little is known about these islands. There is only one described species from Seram Island, i.e., Trigonopterus ellipticus (Pascoe) (Riedel 2011), though several undescribed species from Halmahera and Ternate Islands were included in the phylogeny of the genus published by Tänzler et al. (2016).
Here, we present the results of a recent survey of the Tanimbar Archipelago, or simply Tanimbar. Tanimbar is a cluster of islands located approximately halfway between Australia in the south (Darwin area, ca. 320 km distant) and Western New Guinea in the north (ca. 340 km). The island of Timor is ca. 380 km to the west, and the Kai and Aru Islands lie ca. 150 km and 240 km, respectively, to the northeast. The Tanimbar Islands are all low, i.e., below an elevation of 300 meters. The climate is relatively seasonal, and forest cover comprises of seasonal evergreen forest, dry deciduous forest and moist deciduous forest (Laumonier and Nasi 2018). Geologically, Tanimbar belongs to the outer non-volcanic Banda arc formed in the Quaternary (Hall 1998(Hall , 2002. Parts of the islands are covered with early Pleistocene marine deposits and quaternary reefs occur up to 200 m in altitude (De Smet et al. 1989;Charlton et al. 1991), indicating a very recent origin of ca. 1 Ma. During the Pleistocene, the Tanimbar Islands remained insular as they are not connected to the Sahul shelf (Voris 2000). Thus, Tanimbar has been used as a geological calibration point for a phylogenetic analysis of passerine birds (Jønsson et al. 2010).

Materials and methods
This study is based on 222 specimens of Trigonopterus collected on two field trips to the Tanimbar Islands by the first author. Specimens were collected by beating foliage in primary forest. Holotypes were selected from 44 DNA sequenced specimens. DNA was extracted nondestructively as described by Riedel et al. (2010), with proteinase K lysis so that the genitalia of most specimens did not require extra maceration after DNA-extraction and 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 suffi-ciently digested after DNA extraction were macerated in a 10% KOH solution 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. Type depositories are cited using the following codens:
The methods applied for DNA sequencing and sequence analysis are described by Riedel et al. (2010) and Tänzler et al. (2012). Morphological descriptions are 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.
The closest relatives of Tanimbar species were identified by creating an alignment of 1.154 cox1 sequences representing ca. 1000 species and generating a maximum likelihood reconstruction using the program IQTREE (Nguyen et al. 2015, Trifinopoulos et al. 2016. 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 caudally, to adequately illustrate structures of the curved down apex. All photographs were enhanced using the programs 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 GenBank of NCBI (National Center for Biotechnology Information) and the accession numbers are provided under each species, e.g., as "(EMBL # MN322570)".
Notes. This species is closely related to Trigonopterus species 773 from New Guinea, which differs by having a more distinct punctation and 15.1% p-distance of its cox1 sequence.
Notes. This species is closely related to the undescribed species 437 from Kai Kecil Island from which it differs by the elytral color and a 13.6% p-distance of its cox1 sequence.
Notes. This species is closely related to the undescribed Trigonopterus species 436 from Kai Kecil Island, from which it differs by a larger body size and a more densely punctate pronotum and an 8.9% p-distance of its cox1 sequence. Diagnostic description. Holotype. Male (Fig. 6a). Length 3.06 mm. Color of antennae and tarsi ferruginous, remainder black. Body slender subovate; profile dorsally convex; in dorsal aspect and in profile with weak constriction between pronotum and elytron. Rostrum dorsally with median ridge somewhat flattened at level of antennal insertion; with fine submedian ridges; in basal 1/2 with dense silvery scales, in apical 1/2 with suberect setae. Pronotum densely punctate; punctures becoming larger anterolaterad; each puncture containing short seta; with subglabrous midline. Elytra with striae marked by rows of small punctures and fine hairlines; basal margin bordered by transverse row of deeper punctures; intervals subglabrous, with interspersed minute punctures. Femora with anteroventral ridge weakly crenate, ending in apical half with small tooth. Metafemur dorsally with recumbent silvery scales; dorsoposterior edge indistinct, weakly denticulate-crenate, subapically with stridulatory patch. Abdominal ventrites 1-2 concave, coarsely punctate, at middle subglabrous; ventrite 5 with shallow impression, densely punctate, sparsely setose, laterally with sparse scale. Penis (Fig. 6b) with sides subparallel, apex subangulate, setose; transfer apparatus complex; sclerites of Etymology. This epithet is an adjective derived from the Tanimbar Archipelago.
Notes. This species appears related to a species from New Guinea (species 959) from which it is differs by 19.9% p-distance of its cox1 sequence and many morphological characters.
Note. This species is closely related to Trigonopterus species 60 from Papua New Guinea from which it differs by the structure of the penis and a 17.8% p-distance of its cox1 sequence.

Discussion
Trigonopterus had hitherto been recorded from Ceram Island (Riedel 2011), Flores of the Lesser Sunda Islands (Riedel et al. 2014), the Aru Islands (Pascoe 1885), Eastern Australia , and New Guinea (Riedel 2011, Riedel et al. 2013b). The newly discovered Trigonopterus fauna of the Tanimbar Islands fills a gap in the known distribution and is of special interest due to the isolated position and recent geological age of these islands. The islands of Sumba, Alor, Timor, and Wetar should be searched for additional undescribed species in future. All the discovered species of Tanimbar Trigonopterus live on foliage, and no edaphic lineage could be found. This may be due to the relatively dry climatic conditions, which may be putting stress on species that depend on a layer of moist litter. Alternatively, it is possible, that edaphic species are present but have eluded discovery so far; sifting of leaf litter under the right conditions, e.g., after sufficient rainfalls, may bring them to light.
Morphologically the Tanimbar Trigonopterus species are very different from each other, a fact supported by the molecular dataset of their cox1 sequences. Therefore, no closely related species pairs can be recognized, i.e., there is no indication for any autochthonous speciation on the Tanimbar Archipelago. Instead, the Trigonopterus fauna has been formed largely by repeated dispersal from neighboring regions, i.e., from Western New Guinea and the Moluccas. With its close proximity to Australia, stronger ties to the Australian fauna could be expected, but apparently this is not the case. An explanation could be that the Australian species are largely restricted to the Cape York Peninsula and the east coast of Queensland, which is quite distant from the Tanimbar Islands, and that the absence of Trigonopterus from the Northern Territory in Australia could be a real gap in the distribution of the genus and not just a sampling artifact, caused by environmental extremes.
All in all, the observed composition of the Trigonopterus fauna of the Tanimbar Archipelago is exactly what can be expected from the geological setting and what has been observed in other taxa (How and Kitchener 1997;Beck et al. 2006;Michaux 2010;Andersen et al. 2013): 1) a relatively recent origin that may not have allowed for local speciation and 2) an insular situation not compromised by periods of low sea level. This is quite different in the otherwise similar Aru Islands further east which were part of the continuous Sahul shelf during the Pleistocene. However, no focused fieldwork has ever been carried out on the Aru Islands, from which only T. oblongus Pascoe is known to date. Presumably, further collecting on these islands would discover additional species with stronger ties to the Southern Papuan fauna.
The rapid and ongoing anthropogenic activities in Tanimbar, i.e., agriculture and forestry, put pressure on the natural forests of the islands, which are the exclusive habitats of Trigonopterus species. The first author found the southern part of Yamdena Island to be extensively logged, and most areas of the eastern coast have been converted to agriculture and settlements. The forests of Larat Island are also severely affected by agriculture, with coconut plantations prevalent inside the wildlife conservation area. Finally, Selaru Island without any protected areas, has suffered worst from logging; its interior has already been turned into grassland and the remaining forests areas are fragmented on the sparse rocky soil that is almost useless for gardening. Such destructions of natural forest areas in Tanimbar threaten not only the endemic Trigonopterus species but also the remaining biodiversity of this fascinating archipelago.
RPN to use their wonderful field station, Suprayitno (Denpasar) for the companionship during the first trip, and I Nyoman Sumerta (InaCC), Ruby Setiawan (InaCC), and the people of Lorulun, Adaut, and Keliobar for helping RPN during the fieldwork. Sequencing runs were done by A. Brachmann and G. Brinkmann of the LMU sequencing unit (Munich). This work was funded by the German Academic Exchange Service DAAD (91654661 to R.P.N.), pilot project funding from the laboratory of Michael Balke, DIPA KSK Pengembangan Database KEHATI PDII 2018 and the German Research Foundation DFG (RI 1817/3-4 to A.R.).