Skip to main content
    • Aa
    • Aa

Functional significance of elaborate secondary sexual traits and their evolution in the water strider genus Rheumatobates1

  • Locke Rowe (a1), Kathleen P. Westlake (a2) and Douglas C. Currie (a3)

Sexual conflict may drive the evolutionary elaboration of sexually antagonistic traits that function in mating interactions. One of the most striking cases of elaboration of male morphology occurs in the water strider genus Rheumatobates Bergroth (Hemiptera: Gerridae). The functional significance of the bizarre modifications of appendages in this group is not known. Here we focus on one of the more elaborate of the species, R. rileyi Bergroth. We conduct observational and experimental studies aimed at determining the general sequence of mating behaviour, the role of females in the outcome of sexual interactions, and the functional significance of the highly modified appendages of males. We also map these traits on a known phylogeny of the genus to determine their pattern of evolution. Males repeatedly harass females and females respond with evasive skating or, if the male successfully grasps her, with a premating struggle. The dynamics of the struggle determine the success of mating attempts. Short struggles typically lead to mating, and long struggles typically result in disengagement of the pair. Following a short period of copulation, males withdraw their genitalia and dismount. Females that have been isolated from males for a period of time become less reluctant to mate. During the premating struggle, the antennae of males are used to grasp the females around the head, and the rear legs are used to lift the females' rear legs off the water surface. Neither antennae nor rear legs are used during copulation, thus they are not used for copulatory courtship. Mapping of these traits on the phylogeny indicates multiple independent origins and a pattern of escalation (16 origins, 7 losses). We conclude that these bizarre traits of males are sexually antagonistic and have evolved repeatedly in the genus.


Les conflits sexuels peuvent favoriser le développement au cours de l'évolution de caractères sexuels antagonistes qui servent durant les interactions de l'accouplement. Un des cas les plus remarques de l'élaboration de caractères morphologiques chez le mâle s'observe chez les patineurs du genre Rheumatobates Bergroth (Hemiptera : Gerridae). La signification fonctionnelle des modifications bizarres des appendices dans ce groupe reste inconnue. Nous traitons ici principalement d'une des espèces les plus développés à ce titre, R. rileyi Bergroth. Des observations et des expériences nous servent à déterminer la séquence générale du comportement d'accouplement, le rôle des femelles dans l'issue des interactions sexuelles et la signification fonctionnelle des appendices fortement modifiés du mâle. Nous plaçons ces caractères sur un arbre phylétique reconnu du genre afin de déterminer leur patron d'évolution. Les mâles harcellent les femelles à répétition et les femelles réagissent en s'éloignant en patinant; cependant, si le mâle réussit à l'attraper, il se produit une échauffourée pré-copulatoire. La dynamique de l'échauffourée détermine le succès de la tentative d'accouplement. Les échauffourées courtes mènent normalement à l'accouplement, alors que les échauffourées prolongées se terminent généralement par la séparation du couple. Après une courte période de copulation, le mâle retire ses organes génitaux et débarque de la femelle. Les femelles qui ont été tenues à l'écart des mâles pendant un certain temps sont moins réticentes à l'accouplement. Durant l'échauffourée pré-copulatoire, les antennes des mâles servent à entourer la tête de la femelle et les pattes postérieures sont utilisées pour soulever les pattes postérieures de la femelles au-dessus de la surface de l'eau. Ni les antennes, ni les pattes postérieures ne servent durant la copulation; elles ne sont donc pas impliquées dans la cour associée à l'accouplement. En reliant ces caractéristiques à la phylogénie, on observe de multiples origines indépendantes et un pattern d'escalade (16 origines et 7 pertes). Nous concluons que ces caractères bizarres des mâles sont des caractères sexuels antagonistes et qu'ils sont apparus à plusieurs reprises chez ce genre.

[Traduit par la Rédaction]

Corresponding author
2 Corresponding author (e-mail:
Hide All

This paper is part of a special issue honouring Geoffrey G.E. Scudder for his significant contributions to entomology in Canada.

Linked references
Hide All

This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

N.M. Andersen 1997. A phylogenetic analysis of the evolution of sexual dimorphism and mating systems in water striders (Hemiptera: Gerridae). Biological Journal of the Linnean Society, 61: 345368.

G. Arnqvist 1989. Sexual selection in a water strider: the function, mechanism of selection and heritability of a male grasping apparatus. Oikos, 56: 344350.

G. Arnqvist 1992. Precopulatory fighting in a water strider: intersexual conflict or mate assessment? Animal Behaviour, 43: 559567.

G. Arnqvist , and T. Nilsson 2000. The evolution of polyandry: multiple mating and female fitness in insects. Animal Behaviour, 60: 145164.

G. Arnqvist , and L. Rowe 1995. Sexual conflict and arms races between the sexes: a morphological adaptation for control of mating in a female insect. Proceedings of the Royal Society of London Series B: Biological Sciences, 261: 123127.

G. Arnqvist , and L. Rowe 2002. Antagonistic coevolution between the sexes in a group of insects. Nature (London), 415: 787789.

J. Bergsten , A. Toyra , and A.N. Nilsson 2001. Intra-specific variation and intersexual correlation in secondary sexual characters of three diving beetles (Coleoptera: Dytiscidae). Biological Journal of the Linnean Society, 73: 221232.

T. Chapman , G. Arnqvist , J. Bangham , and L. Rowe 2003. Sexual conflict. Trends in Ecology and Evolution, 18: 4147.

W.G. Eberhard 1985. Sexual selection and animal genitalia. Harvard University Press, Cambridge, Massachusetts.

S. Gavrilets , G. Arnqvist , and U. Friberg 2001. The evolution of female mate choice by sexual conflict. Proceedings of the Royal Society of London Series B: Biological Sciences, 268: 531539.

B. Holland , and W.R. Rice 1998. Perspective: Chaseaway sexual selection: antagonistic seduction versus resistance. Evolution, 52: 17.

J.M. Koene , and H. Schulenburg 2005. Shooting darts: coevolution and counter-adaptation in hermaphroditic snails. BMC Evolutionary Biology, 5: 25.

M.J. Lauer 1996. Effect of sperm depletion and starvation on female mating behavior in the water strider, Aquarius remigis. Behavioral Ecology and Sociobiology, 38: 8996.

A. Ortigosa , and L. Rowe 2002. The effect of hunger on mating behaviour and sexual selection for large male size in Gerris buenoi. Animal Behaviour, 64: 369375.

A. Ortigosa , and L. Rowe 2003. The role of mating history and male size in determining mating behaviours and sexual conflict in a water strider. Animal Behaviour, 65: 851858.

G.A. Parker 1979. Sexual selection and sexual conflict. InSexual selection and reproductive competition in insects. Edited byM.S. Blum and N.A. Blum . Academic Press, New York. pp. 123166.

L. Rowe 1992. Convenience polyandry in a water strider: foraging conflicts and female control of copulation frequency and guarding duration. Animal Behaviour, 44: 189202.

L. Rowe 1994. The costs of mating and mate choice in water striders. Animal Behaviour, 48: 10491056.

L. Rowe , and T. Day 2006. Detecting sexual conflict and sexually antagonistic coevolution. Philosophical Transactions of the Royal Society B: Biological Sciences, 361: 277285.

L. Rowe , G. Arnqvist , A. Sih , and J. Krupa 1994. Sexual conflict and the evolutionary ecology of mating patterns: water striders as a model system. Trends in Ecology and Evolution, 9: 289293.

L. Rowe , E. Cameron , and T. Day 2005. Escalation and retreat during sexually antagonistic coevolution. American Naturalist, 165(S5): 518.

S.K. Sakaluk , P.J. Bangert , A.K. Eggert , C. Gack , and L.V. Swanson 1995. The gin trap as a device facilitating coercive mating in sagebrush crickets. Proceedings of the Royal Society of London Series B: Biological Sciences, 261: 6571.

R. Thornhill 1984. Alternative hypotheses for traits believed to have evolved by sperm competition. InSperm competition and the evolution of animal mating systems. Edited byR.L. Smith . Academic Press, Orlando, Florida.

K. Vepsäläinen , and R. Savolainen 1995. Operational sex ratios and mating conflict between the sexes in the water strider Gerris lacustris. American Naturalist, 146: 869880.

I. Weigensberg , and D.J. Fairbairn 1994. Conflicts of interest between the sexes: a study of mating interactions in a semiaquatic bug. Animal Behaviour, 48: 893901.

K.P. Westlake , and L. Rowe 1999. Developmental costs of male sexual traits in the water strider Rheumatobates rileyi. Canadian Journal of Zoology, 77: 917922.

K.P. Westlake , L. Rowe , and D.C. Currie 2000. Phylogeny of the water strider genus Rheumatobates (Heteroptera: Gerridae). Systematic Entomology, 25: 125145.

S. Wing , J.E. Lloyd , and T. Hongtrakul 1983. Male competition in Pteroptyx fireflies: wing-cover clamps, female anatomy, and mating plugs. Florida Entomologist, 66: 8691.

Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

The Canadian Entomologist
  • ISSN: 0008-347X
  • EISSN: 1918-3240
  • URL: /core/journals/canadian-entomologist
Please enter your name
Please enter a valid email address
Who would you like to send this to? *