Allodessus oliveri

fig. 1: Allodessus bistrigatus (?=A. oliveri), body length 2.8 mm

fig. 2: Allodessus bistrigatus (?=A. oliveri), body length about 3 mm

Taxonavigation

Ordo: Coleoptera
Familia: Dytiscidae

Name

• Allodessus oliveri (Ordish, 1966) Wikispecies link

Notes

• this nominal species poses something of a taxonomic problem
• it was described from the Kermadec Islands (as Liodessus oliveri), and thought until recently to be endemic to these islands
• it was transferred to Allodessus by Balke & Ribera (2004: 123), who considered it to be doubtfully distinct from Allodessus bistrigatus (known from Australia and Tonga), but they made no formal synonymy
• no Allodessus were known from the New Zealand mainland until I started finding them in the early 2000s, commonly in urban ponds in Auckland City (Newmarket Park, Auckland Domain, Tamaki Campus), and there is a single specimen in AMNZ from Great Barrier Island, collected at about the same time
• see figs. 1 and 2 for two specimens of Allodessus found by me in 2010/2011 in the pond at Tamaki Campus, University of Auckland
• I sent one specimen, from Newmarket Park pond, to Michael Balke, and the record was published by Balke & Ribera (2004: 123) as Allodessus oliveri, the first record of this nominal species from anywhere other than the Kermadecs, and the first record of the genus Allodessus from New Zealand
• it is important to note that although only this single specimen record from the New Zealand mainland (Newmarket Park) has been published, this is due to the fact that I only sent one of my specimens to Michael Balke, but the species is common here, and I have deposited a good series in the major N.Z. collections
  • NOTE: Maddison in Macfarlane et al. (2010: 412) list Allodessus oliveri as a possible synonym of Allodessus bistrigatus, but confuse matters somewhat by marking it with a K (=Offshore island endemic: Kermadec Islands)
• given that there has been a reasonable amount of attention paid in the past to N.Z. dytiscids, it seems unlikely that a species this common would have been overlooked on the mainland, so I suspect it to be a recent establishment
• it is unclear to me if the mainland Allodessus derive from the Kermadecs (Balke's view), or independently from Australia
• in summary, in the New Zealand subregion, the genus Allodessus is present on the Kermadecs and on the mainland
• on the Kermadecs it may be native
• on the New Zealand mainland, it may be adventive, as it is common in urban Auckland, and yet it does not appear to have been collected before the year 2000, despite a reasonable amount of attention having been paid to New Zealand dytiscids in the past
• if A. oliveri is a distinct species, then it may be endemic to the Kermadecs, or to the Kermadecs and the New Zealand mainland, but as noted above, it seems more likely that the mainland Allodessus is adventive, so at least it could be A. bistrigatus, and indications are that the Kermadecs Allodessus is also just A. bistrigatus anyway, though it appears to have been present on the Kermadecs for a very long time
• this case illustrates the need for better long-term invertebrate monitoring in New Zealand, for we may never know with any certainty how long Allodessus has been present on the New Zealand mainland, and it may well have remained unnoticed were it not for my efforts in collecting and identifying the local fauna*, though I cannot say if it was present before I started taking more careful notice of small Coleoptera in the early 2000s. It is somewhat ironic that it is present in ponds in both Auckland Domain and on the Tamaki Campus, both places having entomology departments on site (AMNZ and NZAC respectively) ...

* It is worth noting here that I also discovered two other apparently overlooked and presumably adventive water beetles to be common in urban Auckland ponds. One of them, Hydraena ambiflagellata, was known from just a few records from south of Auckland (Delgado & Palma, 1997). The other, Enochrus maculiceps, was not known from New Zealand at all, and despite being very common, its presence here remains unpublished

References

• Balke, M.; Ribera, I. 2004: Jumping across Wallace's line: Allodessus Guignot and Limbodessus Guignot revisited (Coleoptera: Dytiscidae, Bidessini) based on molecular-phylogenetic and morphological data. Australian journal of entomology, 43(2): 114-128. doi PDF PDF
• Delgado, J.A.; Palma, R.L. 1997: A new species and new records of Hydraena (Coleoptera: Hydraenidae) from New Zealand. New Zealand entomologist, 20: 29–36.
• Macfarlane, R.P. et al. 2010: [Chapter] NINE Phylum ARTHROPODA SUBPHYLUM HEXAPODA Protura, springtails, Diplura, and insects. Pp. 233-467 in Gordon, D.P. (ed.): New Zealand inventory of biodiversity. Volume 2. Kingdom Animalia. Chaetognatha, Ecdysozoa, ichnofossils. Canterbury University Press, Christchurch, New Zealand. ISBN 978-1-87725793-3
• Ordish, R.G. 1966: A systematic revision of the New Zealand water beetles (Coleoptera: Dytiscidae). Records of the Dominion Museum, 5: 217-264. BUGZ
• Ordish, R.G. 1976: Water beetles of the Kermadec Islands (Dytiscidae and Hydrophilidae). New Zealand entomologist, 6(2): 155–156. PDF

Stephen Thorpe 00:08, 11 January 2011 (CET)