Xixuthrus ganglbaueri Lameere, 1912

Yanega, Douglas, Olson, David, Shute, Sharon & Komiya, Ziro, 2004, The Xixuthrus species of Fiji (Coleoptera: Cerambycidae: Prioninae), Zootaxa 777 (1), pp. 1-10 : 4-6

Xixuthrus ganglbaueri Lameere, 1912

Figs. 1–2

Specimens examined: Neotype female (here designated), " Fiji, Viti Levu , Tamavua FSN, 28.v.2003, coll. Salanieta Tawake ", " NEOTYPE Xixuthrus ganglbaueri Lameere , det. D. Yanega 2003" (originally from MAFF; will be permanently deposited in BPBM, as type #16557) [ Figs. 1, 2 ]; 1 female, Fiji, Viti Levu, Nasinu, 05.v.81, coll. Marika Rasekaseka ( MAFF); 1 female, same locality, 01.viii.88, coll. A. Vosanibola ( MAFF); other specimens known only from photographs.

Diagnosis: This species can easily be confused with heros (with which it is sympatric; both species are presently confirmed only from Viti Levu, primarily the SE quadrant of the island), though careful examination reveals that it differs in numerous characters, ultimately uniquely sharing little more than the broad glabrous elytral stripes. The major differences (compare Figs. 2 and 4 ) include the lack of prickly spicules on the antennal scape, which is instead covered with distinct, shallow punctures; the scape is only gradually and slightly enlarged apically, in distinct contrast to the apically swollen scape in heros and terribilis ; much shorter antennae relative to body length; there is a glabrous, impunctate, diamond­shaped area in the center of the pronotum; and, in particular, the forebasitarsi are scarcely longer than broad (the mid and hind basitarsi are similarly proportioned, but the difference between ganglbaueri and the other species is more evident in the foretarsi). Additionally, the posterior portion of the head is not as elongated, nor are the mandibles; the mandibular teeth are much smaller; the frontal groove is rather deeply impressed from the clypeus up to the vertex; the distal tarsomere is relatively shorter; the pronotal surface is more generally shining, with the medial ridges generally weaker but more strongly produced and somewhat tuberculate posteriorly. The general coloration of the pubescence is more grayish, or somewhat silvery, in comparison to the usual coloration of heros , which is more brownish to golden, but this difference is somewhat less evident in more worn specimens.

Remarks: The female chosen as the neotype is considered appropriate for two reasons: (1) this is the specimen from which a mesotarsus was removed for sequencing while it was still alive, and it is the genetic voucher for the species, and (2) given Lameere's original claim that the species resembled helleri , and the description of the antennae and foretarsi, the evidence supports that the neotype is in fact the same species that Lameere originally described. The alternative hypothesis, that ganglbaueri was a mislabeled New Guinean species, and there just happens, by coincidence, to be an undiscovered Fijian species which shares several features with it, is far less acceptable. New Guinean specimens which Tippmann identified as ganglbaueri have proven, upon examination (by S.S.), to be helleri . We have seen only a photograph of one male which could definitively be associated with the female, and it also possesses short forebasitarsi, short antennae, strong pronotal ridges, and grayish pubescence (though not clear, it does seem that the photo shows a punctate scape, and central glabrous pronotal spot, but to be cautious we do not use these features in the key below); it is possible that other males may be more difficult to distinguish from male heros , but at least this one specimen is readily separable. We further note that the shorter head, mandibles, and antennae of ganglbaueri are not an artifact of the specimens being smaller than those of heros (i.e., the differences are not due to allometry), even though the average size appears slightly smaller; the neotype female is nearly 9 cm, while the heros female figured is 11 cm, and the differences are independent of the size of heros individuals used for comparison (several of which were in fact smaller).

Gene sequencing (performed by David Hawks) leaves no doubt whatsoever that this specimen is not conspecific with X. heros from the same general locality; the number of base pair differences and large number of insertions (54 base pair changes and 49 insertions in ribosomal 28S regions D2 and D5) constitute as substantial a genetic difference as is sometimes seen between different genera in other families of beetles (Hawks & Heraty, in prep.). The numerous genome insertions suggest that ganglbaueri is the more derived taxon, and we expect to find that when terribilis is sequenced, it will prove to be the sister taxon to heros , rather than ganglbaueri .

Figures

FIGURES 1–6. 1–2. Xixuthrus ganglbaueri Lameere, female neotype: 1, habitus; 2, head, protho­ rax, and forelegs. 3–4. X. heros (Heer): 3, male; head and prothorax; 4, female; head, prothorax, and forelegs. 5–6. X. terribilis Thomson: 5, male holotype of terribilis; head and prothorax; 6, male holotype of heyrovskyi Tippmann [= terribilis]; head.