[Taxacom] Ghost moth as a subduction zone weed

Kenneth Kinman kinman at hotmail.com
Tue Sep 1 03:46:11 CDT 2020

Hi John,
       I guess we probably won't know any time soon, but my prediction is that Phassodes does occur in New Guinea (and that it probably originated there).  That would have given the genus a solid piece of land for its entire history, and help explain its ability to survive the less permanent nature of the volcanic islands to the east.   Therefore, the spread of this genus across these islands could well have happened well after it originated.  And the metapopulation dynamics probably less complex than a genus that was truly endemic to the volcanic islands.

From: John Grehan <calabar.john at gmail.com>
Sent: Saturday, August 29, 2020 9:40 AM
To: Kenneth Kinman <kinman at hotmail.com>
Cc: taxacom <taxacom at mailman.nhm.ku.edu>
Subject: Re: [Taxacom] Ghost moth as a subduction zone weed

Hi Ken,

Occurrence in New Guinea is a perfectly reasonable possibility, although geographic proximity is not always a predictor of occurrence in this region as there are many well known taxa that occur on surrounding islands but skip New Guinea itself. Admittedly in the case of Phassodes this is an insect that is not well known or extensively collected, even from Fiji where it has been mostly recorded (and even then only from one of the two main islands - perhaps because one has the international airport and most collectors stay with that island). The moth is probably very abundant in all localities, but appears to be rare or infrequent at light. On that basis and given the new Solomons record it is reasonable to suppose that its distribution range could be more extensive. However, New Guinea itself has been quite well collected for Lepidoptera for more than a century and while other ghost moths have turned up (but only three genera so far, and all also present in Australia) I would put money (if I had any to spare) on the absence being real.

The current range of Phassodes does conform to a pattern of other non-New Guinea distributions that extend north of New Guinea between the Philippines and Fiji-Tonga, including a group of frogs. My present anticipation is that Phassodes is really part of that pattern. The outstanding question is to what extent that range includes or not the more northwestern islands of Bougainville, New Britain, and New Ireland. If one were to consider geographic proximity it would be these islands are much closer than New Guinea. They currently have no records of any ghost moths as was noted by collectors very early in the literature. If Phassodes were to one day turn up in New Britain region of New Guinea, I would see e the northern margin, particularly the Finistere Range as more of a possibility, but there is a major biotic difference between New Guinea and New Britain in other groups, including (if I recall the number correctly) a 70% difference in the bird fauna, even though the geographic gap is very small.

What is needed (as far as Phassodes might be concerned) is future collecting that includes a focus on ghost moths (that might fly at dusk for example) in the rest of the Solomons as well as further north. I guess that it is not likely in my lifetime. The Solomons specimen turned up entirely by fortuitous accident when my co-author visited an insect fair in Europe some years ago and saw the specimen for sale by a commercial collector. Right place and right time or this occurrence may still have remained obscure. Ghost moth taxonomy is sometimes like running in the dark.

John Grehan

On Fri, Aug 28, 2020 at 9:19 PM Kenneth Kinman via Taxacom <taxacom at mailman.nhm.ku.edu<mailto:taxacom at mailman.nhm.ku.edu>> wrote:
Hi John,
        Interesting.  But now that there has finally been one specimen discovered in the Solomon Islands, wouldn't it seem somewhat likely that there are also species of Phassodes in Papua New Guinea that have not yet been discovered.   The Solomon Islands are closer to New Guinea than they are to Fiji and Samoa.

From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu<mailto:taxacom-bounces at mailman.nhm.ku.edu>> on behalf of John Grehan via Taxacom <taxacom at mailman.nhm.ku.edu<mailto:taxacom at mailman.nhm.ku.edu>>
Sent: Friday, August 28, 2020 1:50 PM
To: taxacom <taxacom at mailman.nhm.ku.edu<mailto:taxacom at mailman.nhm.ku.edu>>
Subject: [Taxacom] Ghost moth as a subduction zone weed

For those interested, following article provides a biogeographic model for
the origin of a ghost moth genus (Phassodes) endemic to some Pacific
oceanic islands. Accessible at

  Taxonomic revision and biogeography of Phassodes Bethune-Baker, 1905
(Lepidoptera: Hepialidae), ghost moth descendants of a subduction zone weed
in the south-west Pacific. Grehan, J.R. & Mielke, C.G.C. Bishop Museum
Occasional Papers 136: 1–37 (2020)

 Abstract. Phassodes Bethune-Baker, 1905 is distributed in Fiji (P.
vitiensis (Rothschild, 1895)), the Solomon Islands (P. walteri sp. n.),
Samoa (P. samoa sp. n.), and American Samoa (P. tutuila sp. n.). It is the
only genus of Hepialidae endemic to oceanic islands. Monophyly of the genus
is supported by four unique features, and a sister group relationship with
the Australian genus Abantiades Herrich-Schäffer, 1855 is supported by four
shared derived features. There are also some features shared between
Phassodes and other genera: a) the southern Andean genus Andeabatis Nielsen
& Robinson, 1983 (shape and structure of the male genitalia), b) the
Peruvian Viridigigas Grehan & Rawlins, 2016 and c) the Chilean Puermytrans
Viette, 1951 (presence of a basal forewing scent gland). The distribution
of Phassodes coincides with the Vitiaz Trench, an extinct subduction zone
that marks a former boundary between the Indo-Australian and Pacific
plates. It is proposed that the common ancestor of Phassodes and Abantiades
diverged through vicariance when the subduction zone along the east coast
of Australia (East Gondwana), along with its island arc, began retreating
into the Pacific between 90 and 75 Ma. Survival of the genus on volcanic
islands is attributed to metapopulation dynamics, with continuous
transference of populations from older, subsiding islands to newly emergent
ones. This model suggests that Phassodes species originated much earlier
than the individual islands they now occupy.

More information about the Taxacom mailing list