Philaccolilus Guignot, 1937

Balke, Michael, Panjaitan, Rawati, Surbakti, Suriani, Shaverdo, Helena, Hendrich, Lars, Van Dam, Matthew H. & Lam, Athena, 2022, NextRAD phylogenomics, sanger sequencing and morphological data to establish three new species of New Guinea stream beetles, Alpine Entomology 6, pp. 51-64 : 51

Genus Philaccolilus Guignot, 1937

Diagnosis.

Laccophilinae with simple (pointed) metatibial spurs, simple lanceolate prosternal process (not trifid) (Fig. 8E ), posteromedial pronotal margin more or less straight, elytral microreticulation with small transverse cells, metacoxal lines slightly diverging anteriorly (Fig. 8E ), metatarsal lobes relatively long (hind tarsi therefore appearing broad, oar like) (Fig. 8E ), without metacoxal/metafemoral stridulation device ( Miller and Bergsten 2016) (Fig. 8E ). Dorsal surface dark, with contrasting yellow / orange pattern, or completely black. The dorsal color pattern is usually delineating species (except for P. irianensis and P. incognitus , Fig. 1F, G ). The extend of the paler markings can vary within species (e.g. Fig. 1J, K ) and even left/right side in an individual, but not so the principal position and overall shape of the pattern. Therefore, the examination of multiple specimens is recommended. Penultimate ventrite with tuft of long golden setae medially. The median lobe of aedeagus is of, generally speaking, simple structure, i.e. simply curved sclerotized structure (e.g. Figs 6 , 7 ).

Taxonomic decisions based on multiple data sources.

The two lineages from different parts of the Bird’s Head, "P. band" and "P. black" ( Lam 2017) are genetically very similar. Based on CO1 data, the Arfak and Tamrau Mts. populations (Figs 4 , 5C ) are geographically structured, but only based on a low CO1 divergence. Based on that, their geographic distribution, clearly different body size and elytral color pattern, we suggest that they represent two species that evolved only recently in the two different mountain areas of the Bird’s Head, after their ancestral species colonized that area out of the main body of New Guinea island.

What was so far referred to as Philaccolilus ameliae is a complex of at least three species. While morphological differences are subtle, both nextRAD and CO1 data clearly delineate three clades that we here assign species status. Philaccolilus ameliae is known from eastern and central New Guinea. Philaccolilus febrina is described from the Bird’s Head (Fig. 5A ). Philaccolilus weylandensis (new status) was described as a subspecies of P. ameliae from the west of New Guinea (Weyland Mts.) and was later also found in the Digul River on the southern slopes of the central range, more in the center of New Guinea (Fig. 4 ). Populations from these two localities are genetically differentiated and might in fact represent two species. We leave them assigned to Philaccolilus weylandensis , expecting additional samples from along the southern slopes of the central range. It is interesting to note that the only locality between Digul River and Weyland Mts. revealed a population of Philaccolilus ameliae (Fig. 5B ). This hints to more complex diversification and biogeographic patterns in this complex, that requires additional fieldwork.

Figures

Figure 1. A-L. Dorsal habitus of Philaccolilus species, appendages mostly removed; brightness of paler spots digitally slightly enhanced for clarity, without altering the basic color tone.

Figure 4. Distribution of Philaccolilus species in New Guinea. Dots - P. ameliae complex, stars - P. kirana and P. intania here described from the Bird's Head Peninsula.

Figure 5. Results of the genomic nextRAD as well as mitochondrial DNA CO 1 data sequencing of Philaccolilus species in New Guinea. A. P. febrina in the Bird's Head Pensinsula; B. P. ameliae and P. weylandensis in New Guinea main body; C. P. kirana and P. intania from the Bird's Head Peninsula (localities see A). Results of the structuring analysis of nextRAD data depicted as barplots, the CO 1 data as haplotype network, subs. = substitutions.

Figure 6. Median lobe of aedeagus of Philaccolilus species A, B. P. kirana; C, D. P. intania.

Figure 7. Median lobe of aedeagus of Philaccolilus species (left, lateral, right, ventral view) A, B. P. ameliae (from Brazza River); C, D. P. ameliae (paratype from Wau); E, F. P. febrina (from Tamrau Mts.); G, H. P. weylandensis (from Weyland Mts.); I, J. P. weylandensis (from Digul River).

Figure 8. Last male and female ventrite of Philaccolilus A, B. As in P. kirana and P. intania; C, D. As in P. ameliae, P. febrina and P. weylandensis. Not to scale. In C. with last and penultimate ventrites to illustrate the tuft of long golden setae on penultimate ventrite; E. P. febrina male in ventral view, not to scale.