Eur. J. Entomol. 105 (4): 737-750, 2008 | 10.14411/eje.2008.100

On the systematic position of the diving-beetle genus Pachydrus (Coleoptera: Dytiscidae: Hydroporinae): Evidence from larval chaetotaxy and morphology

Mariano C. MICHAT1,2, Patricia L.M. TORRES1
1 CONICET
2 Laboratorio de Entomología, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Av. Int. Güiraldes s/n, Ciudad Universitaria, C1428EHA, Buenos Aires, Argentina; e-mail: marianoide@gmail.com

Phylogenetic relationships within the diving-beetle subfamily Hydroporinae are not well understood. Some authors include the genus Pachydrus Sharp, 1882 in the tribe Hyphydrini, whereas others are in favour of excluding Pachydrus from the Hyphydrini and placing it in its own tribe, Pachydrini. Larval characters have been underutilised in phylogenetic studies, mainly because the larvae of many taxa within the family are unknown. In this study, the phylogenetic relationships of Pachydrus are studied based on a cladistic analysis of 34 taxa and 122 morphological larval characters. For this purpose, larvae of P. obesus Sharp, 1882 are described and illustrated in detail for the first time, with particular emphasis on morphometry and chaetotaxy. First and second instars for the genus were unknown. The results support a monophyletic origin of the tribe Hyphydrini excluding Pachydrus, based on four unique character states. On the other hand, Pachydrus is resolved as the sister group of the Hydrovatini. These results suggest Pachydrus should not be placed in the Hyphydrini. Given that the Hyphydrini minus Pachydrus is a distinctive clade, based on this study, it seems useful to recognise this group as Hyphydrini. Including Pachydrus in Hyphydrini would leave the tribe with a single larval apomorphy, as most characters present in the Hyphydrini and Pachydrus are also present in the Hydrovatini. However, in the absence of larvae of Heterhydrus Fairmaire, 1869 and of a more comprehensive and inclusive analysis, we do not propose a formal exclusion of Pachydrus from Hyphydrini at this stage. Pachydrus is a highly distinctive genus within the Hydroporinae and is characterised by several larval apomorphies.

Keywords: Diving beetles, Dytiscidae, Hyphydrini, Pachydrus, larva, chaetotaxy, phylogeny

Received: January 6, 2008; Accepted: June 4, 2008; Published: October 24, 2008

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References

  1. ALARIE Y. 1989: The larvae of Laccornis Des Gozis 1914 (Coleoptera: Adepaga: Dytiscidae) with description of L. latens (Fall, 1937) and redescription of L. conoideus (Leconte, 1850). Coleopt. Bull. 43: 365-378
  2. ALARIE Y. 1991a: Primary setae and pores on the cephalic capsule and head appendages of larval Hydroporinae (Coleoptera: Dytiscidae). Can. J. Zool. 69: 2255-2265 Go to original source...
  3. ALARIE Y. 1991b: Description of larvae of 17 Nearctic species of Hydroporus Clairville (Coleoptera: Dytiscidae: Hydroporinae) with an analysis of their phylogenetic relationships. Can. Entomol. 123: 627-704 Go to original source...
  4. ALARIE Y. 1995: Primary setae and pores on the legs, the last abdominal segment, and the urogomphi of larvae of Nearctic Colymbetinae (Coleoptera: Adephaga: Dytiscidae) with an analysis of their phylogenetic relationships. Can. Entomol. 127: 913-943 Go to original source...
  5. ALARIE Y. 1997: Taxonomic revision and phylogenetic analysis of the genus Oreodytes Seidlitz (Coleoptera: Dytiscidae: Hydroporinae) based on larval morphology. Can. Entomol. 129: 399-503 Go to original source...
  6. ALARIE Y. 1998: Phylogenetic relationships of Nearctic Colymbetinae (Coleoptera: Adephaga: Dytiscidae) based on chaetotaxic and porotaxic analysis of head capsule and appendages of larvae. Can. Entomol. 130: 803-824 Go to original source...
  7. ALARIE Y. & CHALLET G.L. 2006a: Description of the larva of Primospes suturalis Sharp (Coleoptera: Dytiscidae, Hydroporinae) with implications for the phylogeny of the Hyphydrini. Aquat. Insects 28: 31-46 Go to original source...
  8. ALARIE Y. & CHALLET G.L. 2006b: Larval description and phylogenetic placement of the South African endemic genus Andex Sharp (Coleoptera: Adephaga: Dytiscidae). Ann. Entomol. Soc. Am. 99: 743-754 Go to original source...
  9. ALARIE Y. & DELGADO J.A. 1999: Study of the larvae of Antiporus strigosulus (Broun) (Coleoptera: Dytiscidae) with implications for the phylogeny of the Hydroporini. Aquat. Insects 21: 99-113 Go to original source...
  10. ALARIE Y. & HARPER P.P. 1990: Primary setae and pores on the last abdominal segment and the urogomphi of larval Hydroporinae (Coleoptera: Adephaga: Dytiscidae), with notes on other dytiscid larvae. Can. J. Zool. 68: 368-374 Go to original source...
  11. ALARIE Y. & MEGNA Y.S. 2006: Description of the larva of Cuban specimens of Pachydrus obniger (Chevrolat, 1863) (Coleoptera: Dytiscidae). Koleopt. Rdsch. 76: 43-49
  12. ALARIE Y. & MICHAT M.C. 2007a: Primary setae and pores on the maxilla of larvae of the subfamily Hydroporinae (Coleoptera: Adephaga: Dytiscidae): ground plan pattern reconsidered. Coleopt. Bull. 61: 310-317 Go to original source...
  13. ALARIE Y. & MICHAT M.C. 2007b: Phylogenetic analysis of Hydroporinae (Coleoptera: Dytiscidae) based on larval morphology, with description of first instar of Laccornellus lugubris. Ann. Entomol. Soc. Am. 100: 655-665 Go to original source...
  14. ALARIE Y. & NILSSON A.N. 1997: Larvae of Stictonectes Brinck: generic characteristics, description of S. canariensis Machado, and analysis of phylogenetic relationships with other genera of the tribe Hydroporini (Coleoptera: Dytiscidae). Coleopt. Bull. 51: 120-139
  15. ALARIE Y. & WATTS C.H.S. 2004: Larvae of the genus Antiporus (Coleoptera: Dytiscidae) and phylogenetic implications. Invert. Syst. 18: 523-546. Go to original source...
  16. ALARIE Y., HARPER P.P. & MAIRE A. 1990a: Primary setae and pores on legs of larvae of Nearctic Hydroporinae (Coleoptera: Dytiscidae). Quaest. Entomol. 26: 199-210
  17. ALARIE Y., HARPER P.P. & ROUGHLEY R.E. 1990b: Description of the larvae of eleven Nearctic species of Hygrotus Stephens (Coleoptera: Dytiscidae: Hydroporinae) with an analysis of their phyletic relationships. Can. Entomol. 122: 985-1035 Go to original source...
  18. ALARIE Y., WANG L.J., NILSSON A.N. & SPANGLER P.J. 1997: Larval morphology of four genera of the tribe Hyphydrini Sharp (Coleoptera: Dytiscidae: Hydroporinae) with an analysis of their phylogenetic relationships. Ann. Entomol. Soc. Am. 90: 709-735 Go to original source...
  19. ALARIE Y., NILSSON A.N. & HENDRICH L. 1999: Larval morphology of the palearctic genera Deronectes Sharp and Scarodytes Gozis (Coleoptera: Dytiscidae: Hydroporinae), with implications for the phylogeny of the Deronectes-group of genera. Entomol. Scand. 30: 178-195 Go to original source...
  20. ALARIE Y., NILSSON A.N., HENDRICH L. & WATTS C.H.S. 2000: Larval morphology of four genera of Laccophilinae (Coleoptera: Adephaga: Dytiscidae) with an analysis of their phylogenetic relationships. Insect Syst. Evol. 31: 121-164 Go to original source...
  21. ALARIE Y., CUPPEN J.G.M., HENDRICH L. & NILSSON A.N. 2001a: Description of larvae of Herophydrus musicus (Klug) and analysis of relationships with members of the genus Hygrotus Stephens (Coleoptera: Dytiscidae, Hydroporinae). Aquat. Insects 23: 193-207 Go to original source...
  22. ALARIE Y., WATTS C.H.S. & NILSSON A.N. 2001b: Larval morphology of the tribe Matini (Coleoptera: Dytiscidae: Colymbetinae): descriptions of Batrachomatus daemeli, Matus bicarinatus, and Allomatus nannup and phylogenetic relationships. Can. Entomol. 133: 165-196 Go to original source...
  23. ALARIE Y., MICHAT M.C., ARCHANGELSKY M. & BARBER-JAMES H.M. 2007: Larval morphology of Liodessus Guignot, 1939: generic characteristics, descriptions of five species and comparisons with other members of the tribe Bidessini (Coleoptera: Dytiscidae: Hydroporinae). Zootaxa 1516: 1-21
  24. BERTRAND H. 1968: Larves de coleopteres aquatiques recueillies au Bresil par M.G. Marlier. Bull. Soc. Entomol. Fr. 73: 8-21
  25. BERTRAND H. 1972: Larves et Nymphes des Coleopteres Aquatiques du Globe. F. Paillart, France, 804 pp
  26. BISTROM O. 1982: A revision of the genus Hyphydrus Illiger (Coleoptera, Dytiscidae). Acta Zool. Fenn. 165: 1-121
  27. BISTROM O., NILSSON A.N. & WEWALKA G. 1997: A systematic review of the tribes Hyphydrini Sharp and Pachydrini n. trib. (Coleoptera, Dytiscidae). Entomol. Fenn. 8: 57-82
  28. CRESPO F.A. 1996: Descripcion del tercer estadio larval de Pachydrus obesus Sharp 1882 (Dytiscidae, Coleoptera). Physis (B) 51(120-121): 1-5
  29. GOLOBOFF P., FARRIS J. & NIXON K. 2003: T.N.T.: Tree analysis using new technology. Program and documentation, available from the authors, and at http://www.zmuc.dk/public/phylogeny
  30. KITCHING I.J., FOREY P.L., HUMPHRIES C.J. & WILLIAMS D.M. 1998: Cladistics. The theory and Practice of Parsimony Analysis. 2nd ed. Systematics Association publications; 11. Oxford University Press, New York, 228 pp
  31. LAWRENCE J.F. 1991: Order Coleoptera. In Stehr F.W. (ed.): Immature Insects. Vol. 2. Kendall/Hunt, Iowa, pp. 144-658
  32. MICHAT M.C. 2006: The phylogenetic position of Hydrovatus Motschulsky: evidence from larval morphology of H. caraibus Sharp (Coleoptera: Dytiscidae: Hydroporinae). Insect Syst. Evol. 37: 419-432 Go to original source...
  33. MICHAT M.C. & ALARIE Y. 2006: The larvae of Amarodytes duponti (Aube) (Coleoptera: Dytiscidae: Hydroporinae), with comments on Bidessini larval morphology and chaetotaxy. Zootaxa 1351: 1-13
  34. MICHAT M.C. & ALARIE Y. 2008: Morphology and chaetotaxy of larval Hypodessus cruciatus (Regimbart) (Coleoptera: Dytiscidae: Hydroporinae), and analysis of the phylogenetic relationships of the Bidessini based on larval characters. Stud. Neotr. Faun. Env. 43: 135-146 Go to original source...
  35. MICHAT M.C. & ARCHANGELSKY M. 2007: Descriptions of larvae of Desmopachria Babington (Coleoptera: Dytiscidae: Hydroporinae): the D. vicina Sharp species group. Coleopt. Bull. 61: 264-276 Go to original source...
  36. MICHAT M.C. & TORRES P.L.M. 2005: Larval morphology of Macrovatellus haagi (Wehncke) and phylogeny of Hydroporinae (Coleoptera: Dytiscidae). Insect Syst. Evol. 36: 199-217 Go to original source...
  37. MICHAT M.C. & TORRES P.L.M. 2006a: Hydaticus tuyuensis Tremouilles (Coleoptera: Dytiscidae): larval morphology and phylogenetic relationships within Dytiscinae. Hydrobiologia 563: 479-492 Go to original source...
  38. MICHAT M.C. & TORRES P.L.M. 2006b: The unknown larva of Anodocheilus Babington (Coleoptera: Dytiscidae: Hydroporinae: Bidessini): description of A. maculatus Babington and chaetotaxic considerations. Trans. Am. Entomol. Soc. 132: 431-444
  39. MICHAT M.C., ARCHANGELSKY M. & TORRES P.L.M. 2005: Descriptions of the preimaginal stages of Lancetes marginatus (Steinheil) and L. biremis Riha (Coleoptera: Dytiscidae), and comparative notes with other Lancetes larvae. Stud. Neotr. Faun. Env. 40: 129-142 Go to original source...
  40. MICHAT M.C., ALARIE Y., TORRES P.L.M. & MEGNA Y.S. 2007: Larval morphology of the diving beetle Celina and the phylogeny of ancestral hydroporines (Coleoptera: Dytiscidae: Hydroporinae). Invert. Syst. 21: 239-254 Go to original source...
  41. MILLER K.B. 2001: On the phylogeny of the Dytiscidae (Insecta: Coleoptera) with emphasis on the morphology of the female reproductive system. Insect Syst. Evol. 32: 45-92 Go to original source...
  42. MILLER K.B., WOLFE G.W. & BISTROM O. 2006: The phylogeny of the Hydroporinae and classification of the genus Peschetius Guignot, 1942 (Coleoptera: Dytiscidae). Insect Syst. Evol. 37: 257-279 Go to original source...
  43. NILSSON A.N. 2001: World Catalogue of Insects. Vol. 3. Dytiscidae (Coleoptera). Apollo Books, Stenstrup, 395 pp
  44. SHARP D. 1882: On aquatic carnivorous Coleoptera or Dytiscidae. Sci. Trans. R. Dublin Soc. 2: 179-1003
  45. SHAVERDO H.V. & ALARIE Y. 2006: Description of the larva of Canthyporus kenyensis Bilardo & Sanfilippo (Coleoptera: Dytiscidae: Hydroporinae) with implication for the phylogeny of the Hydroporini. Aquat. Insects 28: 113-130 Go to original source...
  46. SPANGLER P.J. & FOLKERTS G.W. 1973: The larva of Pachydrus princeps (Coleoptera: Dytiscidae). Proc. Biol. Soc. Wash. 87: 351-356
  47. TREMOUILLES E.R. 1995: Dytiscidae: Methlinae - Hydroporinae. In Castellanos Z.A. (ed.): Fauna de Agua Dulce de la Republica Argentina 37(1). Profadu, La Plata, pp. 1-82
  48. WILEY E.O. 1981: Phylogenetics. The Theory and Practice of Phylogenetic Systematics. John Wiley & Sons, New York, 439 pp
  49. WOLFE G.W. 1985: A phylogenetic analysis of plesiotypic Hydroporinae lineages with an emphasis on Laccornis des Gozis (Coleoptera: Dytiscidae). Proc. Acad. Nat. Sci. Phil. 137: 132-155
  50. YOUNG F.N. 1980: Predaceous water beetles of the genus Desmopachria Babington: the subgenera with descriptions of new taxa (Coleoptera: Dytiscidae). Rev. Biol. Trop. 28: 305-321.
  51. ZIMMERMANN A. 1919: Die Schwimmkaefer des Deutschen Entomologischen Museums zu Berlin-Dahlem. Arch. Naturgesch. 83[1917]: 69-249