Eur. J. Entomol. 110 (1): 159-163, 2013 | DOI: 10.14411/eje.2013.022

Male mandible trimorphism in the stag beetle Dorcus rectus (Coleoptera: Lucanidae)

Yutaka IGUCHI
Laboratory of Biology, Yamashita-cho 1-10-6, Okaya City, Nagano Prefecture, 394-0005, Japan; e-mail: bio-igu@f8.dion.ne.jp

Males in many beetles show horn or mandible dimorphism. The stag beetle Dorcus rectus was assumed to have dimorphic males, but in this species there are not two but three visually distinct mandibular phenotypes. The aim of this study is to determine if the three phenotypes represent an allometric trimorphism in this species by studying the scaling relationship between body length and mandible length in 148 adult males and 31 adult females. The relationship was fitted using the following four statistical models; a simple line, a logistic curve, a continuous segmented line and a discontinuous line. The best-fitting model for the males was a discontinuous line with two break points and that for the females a simple line. The male data was also well fitted by a logistic curve. The discontinuous linear model divided the males into three groups that were in good agreement with the three phenotypes. These results suggest that a subtle allometric trimorphism possibly exists in males of this species. Small males of this species have no distinct teeth on their mandibles, whereas small males of D. striatipennis and D. curvidens, which are closely related to D. rectus, have a pair of distinct teeth on their mandibles. The phylogenetic relationship of these Dorcus species suggests that the trimorphism in D. rectus may have arisen through the loss of teeth in small males.

Keywords: Lucanidae, Dorcus rectus, stag beetle, mandible, trimorphism, scaling relationship, discontinuous model

Received: November 11, 2010; Accepted: July 2, 2012; Published: January 2, 2013

Download citation

References

  1. BURNHAM K.P. & ANDERSON D.R. 2002: Model Selection and Multimodel Inference: A Practical Information-Theoretic Approach. 2nd ed. Springer, New York, 488 pp
  2. CLARK J.T. 1977: Aspects of variation in the stag beetle Lucanus cervus (L.) (Coleoptera: Lucanidae). - Syst. Entomol. 2: 9-16 Go to original source...
  3. COOK D. 1987: Sexual selection in dung beetles. I. A multivariate study of morphological variation in two species of Onthophagus (Scarabaeidae: Onthophagini). - Aust. J. Zool. 35: 123-132 Go to original source...
  4. EBERHARD W.G. 1982: Beetle horn dimorphism: making the best of a bad lot. - Am. Nat. 119: 420-426 Go to original source...
  5. EBERHARD W.G. & GUTIERREZ E.E. 1991: Male dimorphism in beetles and earwigs and the question of developmental constraints. - Evolution 45: 18-28 Go to original source...
  6. EBERHARD W.G., GARCIA-CJ.M. & LOBO J. 2000: Size-specific defensive structures in a horned weevil confirm a classic battle plan: avoid fights with larger opponents. - Proc. R. Soc. Lond. (B) 267: 1129-1134 Go to original source...
  7. EMLEN D.J. 1997: Alternative reproductive tactics and maledimorphism in the horned beetle Onthophagus acuminatus (Coleoptera: Scarabaeidae). - Behav. Ecol. Sociobiol. 41: 335-341. Go to original source...
  8. EMLEN D.J. & NIJHOUT H.F. 2000: The development and evolution of exaggerated morphologies in insects. - Annu. Rev. Entomol. 45: 661-708 Go to original source...
  9. EMLEN D.J., HUNT J. & SIMMONS L.W. 2005a: Evolution of sexual dimorphism and male dimorphism in the expression of beetle horns: phylogenetic evidence for modularity, evolutionary lability, and constraint. - Am. Nat. 166: S42-S68 Go to original source...
  10. EMLEN D.J., MARANGELO J., BALL B. & CUNNINGHAM C.W. 2005b: Diversity in the weapons of sexual selection: horn evolution in the beetle genus Onthophagus (Coleoptera: Scarabaeidae). - Evolution 59: 1060-1084 Go to original source...
  11. EMLEN D.J., LAVINE L.C. & EWEN-CAMPEN B. 2007: On the origin and evolutionary diversification of beetle horns. - Proc. Nat. Acad. Sci. USA (Suppl. 1) 104: 8661-8668 Go to original source...
  12. FLEISS J.L. 1971: Measuring nominal scale agreement among many raters. - Psychol. Bull. 76: 378-382 Go to original source...
  13. FLEISS J.L. 1981: Statistical Methods for Rates and Proportions. 2nd ed. Wiley, New York, 321 pp
  14. GOLDSMITH S.K. 1985: Male dimorphism in Dendrobias mandibularis Audinet-Serville (Coleoptera: Cerambycidae). - J. Kans. Entomol. Soc. 58: 534-538
  15. GOLDSMITH S.K. 1987: The mating system and alternative reproductive behaviors of Dendrobias mandibularis (Coleoptera: Cerambycidae). - Behav. Ecol. Sociobiol. 20: 111-115 Go to original source...
  16. HARVEY D.J. & GANGE A.C. 2006: Size variation and mating success in the stag beetle, Lucanus cervus. - Physiol. Entomol. 31: 218-226 Go to original source...
  17. HONGO Y. 2003: Appraising behaviour during male-male interaction in the Japanese horned beetle Trypoxylus dichotomus septentrionalis (Kono). - Behaviour 140: 501-517 Go to original source...
  18. HOSOYA T., ARAYA K. & SHIROTA Y. 2003: Molecular phylogeny of Japanese stag beetles of the genes Dorcus (Coleoptera, Lucanidae) and its allied genera inferred from mitochondrial COI gene sequences. - Elytra 31: 127-142
  19. IGUCHI Y. 1992: Individual variation in males of Macrodorcas rectus (Motshulsky). - Kontyu to Shizen 27: 16-19 [in Japanese]
  20. IGUCHI Y. 1998: Horn dimorphism of Allomyrina dichotoma septentrionalis (Coleoptera: Scarabaeidae) affected by larval nutrition. - Ann. Entomol. Soc. Am. 91: 845-847 Go to original source...
  21. IGUCHI Y. 2001a: Male morphological dimorphism in the stag beetle, Dorcus rectus (Coleoptera: Lucanidae). - Spec. Publ. Jpn Coleopt. Soc. 1: 201-204 Go to original source...
  22. IGUCHI Y. 2001b: Differences in the frequency of fights between minor and major males in the horned beetle Trypoxylus dichotomus septentrionalis (Coleoptera: Scarabaeidae). - Entomol. Rev. Japan 56: 11-14
  23. IGUCHI Y. 2002: Further evidence of male trimorphism in the horned beetle Trypoxylus dichotomus septentrionalis (Coleoptera, Scarabaeidae). - Spec. Bull. Jpn. Soc. Coleopterol. 5: 319-322 Go to original source...
  24. INUKAI T. 1924: Statistical studies on the variation of stag beetles. - Trans. Sapporo Nat. Hist. Soc. 9: 77-91
  25. KAWANO K. 1995: Horn and wing allometry and male dimorphism in giant rhinoceros beetles (Coleoptera: Scarabaeidae) of tropical Asia and America. - Ann. Entomol. Soc. Am. 88: 92-99 Go to original source...
  26. KAWANO K. 1997: Cost of evolving exaggerated mandibles in stag beetles (Coleoptera: Lucanidae). - Ann. Entomol. Soc. Am. 90: 453-461 Go to original source...
  27. KNELL R.J. 2009: On the analysis of non-linear allometries. - Ecol. Entomol 34: 1-11 Go to original source...
  28. KUROSAWA Y., OKAJIMA S. & YAMAGUCHI S. 1988: An Illustrated Book of Japanese Stag Beetles. Hoikusha, Osaka, 207 pp. [in Japanese]
  29. MOCZEK A.P. 2005: The evolution and development of novel traits, or how beetles got their horns. - BioScience 55: 937-951 Go to original source...
  30. MOCZEK A.P. & EMLEN D.J. 2000: Male horn dimorphism in the scarab beetle, Onthophagus taurus: do alternative reproductive tactics favor alternative phenotypes? - Anim. Behav. 59: 459-466 Go to original source...
  31. MOCZEK A.P., HUNT J., EMLEN D.J. & SIMMONS L.W. 2002: Threshold evolution in exotic populations of a polyphenic beetle. - Evol. Ecol. Res. 4: 587-601
  32. MOTULSKY H. & CHRISTOPOULOS A. 2004: Fitting Models to Biological Data Using Linear and Nonlinear Regression: A Practical Guide to Curve Fitting. Oxford University Press, Oxford, 351 pp
  33. RASMUSSEN J.L. 1994: The influence of horn and body size on the reproductive behavior of the horned rainbow scarab beetle Phanaeus difformis (Coleoptera: Scarabaeidae). - J. Insect Behav. 7: 67-82 Go to original source...
  34. ROWLAND J.M. & EMLEN D.J. 2009: Two thresholds, three male forms result in facultative male trimorphism in beetles. - Science 323: 773-776 Go to original source...
  35. SHIOKAWA T. & IWAHASHI O. 2000: Mandible dimorphism in male of a stag beetle, Prosopocoilus dissimilis okinawanus (Coleoptera: Lucanidae). - Appl. Entomol. Zool. 35: 487-494 Go to original source...
  36. SIVA-JOTHY M.T. 1987: Mate securing tactics and the cost of fighting in the Japanese horned beetle, Allomyrina dichotoma L. (Scarabaeidae). - J. Ethol. 5: 165-172 Go to original source...
  37. TATSUTA H., MIZUTA K. & AKIMOTO S. 2001: Allometric patterns of heads and genitalia in the stag beetle Lucanus maculifemoratus (Coleoptera: Lucanidae). - Ann. Entomol. Soc. Am. 94: 462-466 Go to original source...
  38. TATSUTA H., MIZUTA K. & AKIMOTO S. 2004: Relationship between size and shape in the sexually dimorphic beetle Prosopocoilus inclinatus (Coleoptera: Lucanidae). - Biol. J. Linn. Soc. 81: 219-233 Go to original source...
  39. TOMKINS J.L., KOTIAHO J.S. & LEBAS N.R. 2005: Matters of scale: positive allometry and the evolution of male dimorphisms. - Am. Nat. 165: 389-402 Go to original source...