Phassodes, Bethune-Baker, 1905

Grehan, John R. & Mielke, Carlos G. C., 2018, Evolutionary biogeography and tectonic history of the ghost moth families Hepialidae, Mnesarchaeidae, and Palaeosetidae in the Southwest Pacific (Lepidoptera: Exoporia), Zootaxa 4415 (2), pp. 243-275 : 252-254

(4) Phassodes in the Southwest Pacific

Phassodes is the only exoporian genus endemic to small volcanic islands in the Southwest Pacific ( Fig. 10 ). There appear to be different species on each of the islands of American Samoa, Fiji, Samoa and the Solomon Islands (Grehan & Mielke in prep.). Biogeographic connections involving these and other nearby islands are common. Examples include the plant genus Cettia in Tonga, Fiji, Solomons, Bougainville, Palau, Philippines and Europe, but missing Vanuatu; the warbler genus Megalurulus in Fiji, Vanuatu, New Caledonia, Solomons (Guadalcanal), Bougainville, and New Britain; a clade of stick insects in the Cook Islands, Fiji, Solomon Islands, New Guinea, and Lord Howe Island/ Australia; the frog genus Platymantis in Fiji, Solomons Islands, New Guinea, Palau, and the Philippines; the stick insect Phasmotaenia in Fiji, Solomons, New Guinea, Philippines, and Micronesia; the palm

1. The molecular analysis is problematic because it groups Oxycanus sphragidias ( Meyrick, 1890) with Trictena rather than with other oxycanine species. But the male genitalia of Oxycanus sphragidias exhibit only Oxycanus features (J.R.G. personal observation) and so lack any specific resemblance to Trictena (or the related Abantiades ) (cf. Simonsen 2018, for descriptions of all Trictena / Abantiades species). This anomaly places the entire molecular tree in doubt. Direct assessment of possible contamination or other causes of error cannot be assessed, as the voucher specimen for O. sphragidias cannot be located and all frozen specimens appear to have been discarded (John Marris, pers. comm.)

Heterospathe in Fiji, Solomon Islands, New Britain, New Guinea, Maluku Islands, and the Philippines; and the beetle Allorthorhinus in Fiji, Solomon Islands, and Philippines ( Heads 2017a). In the context of these biogeographic relationships it is not unexpected that Phassodes will be found to occur more widely over the northern Melanesian Arc ( Fig. 10 ) and perhaps further west into northern New Guinea and Southeast Asia.

The shared biogeographic pattern encompassing these localities includes dispersal abilities ranging from amphibians that cannot tolerate salt water to birds and cicadas that can fly. This combination suggests that a shared geological history is more important for understanding the origin of these distributions than the purported dispersal ability. The biogeographic origin of Phassodes is therefore attributed to an ancestral distribution that was either part of East Gondwana (and later of the arcs that migrated away from it) or formerly occupied landmasses associated with the large igneous plateaus that broke up within the Pacific plate ( Heads, 2012). Further evidence on the ancestral range of Phassodes could be derived from the location of its sister genus, but this has not yet been identified with any certainty. The Phassodes male has three features that are derived within the Hepialidae : a prominent scent gland at the base of the forewing, specialized scent scales at the base of the hindwing margin (JRG personal observation) and a well developed scent gland on the hind leg. These structures are only known to be found together in Puermytrans from the Andes of southern Chile (Nielsen & Robinson 1984).

The specialized similarities between Phassodes and Puermytrans are not entirely conclusive as these structures also occur in different combinations in some other exoporian taxa. The forewing and hind leg scent glands are both present in Viridigigas of the Peruvian Eastern Andes, but this genus lacks the hindwing scent scales. The forewing scent gland alone is found in the eastern Asian Palpifer while the metatibial scent glands occur alone in several other hepialid genera that collectively do not appear to form a monophyletic group ( Grehan & Rawlins, 2016). There is also a fourth derived feature in the form of a lateral abdominal projection or knob (on the tergosternal sclerites) that is present in Phassodes , a clade of Meso and South American genera (referred to as cibyrines), the Chilean genus Callipielus , and the Australian genus Abantiades ( Grehan 2010) . The female external genitalia of Phassodes exhibit dorsal projections of the lateral lobes (observed by authors) that do not occur in Abantiades or any other Southwestern Pacific Hepialidae but are also present in some New World genera. A close relationship between Phassodes and genera in both Australia and South America would be consistent with a well-known trans- Pacific distribution pattern ( Heads 2012, 2014, 2017a).

Figures

FIGURES 9–10. Fig. 9. Distribution of oxycanine groups: Neohepialiscus (North Africa), Hepialiscus (Himalaya-southern Asia), Napialus (China), Oxycanus (New Guinea-Australia), and New Zealand oxycanine genera. Fig. 10. Known and potential distribution of Phassodes.