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Sexual conflicts, loss of flight, and fitness gains in locomotion of polymorphic water striders
Author(s) -
Goodwyn Pablo Perez,
Fujisaki Kenji
Publication year - 2007
Publication title -
entomologia experimentalis et applicata
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 83
eISSN - 1570-7458
pISSN - 0013-8703
DOI - 10.1111/j.1570-7458.2007.00571.x
Subject(s) - gerridae , biology , wing , heteroptera , zoology , habitat , ecology , sexual dimorphism , insect , context (archaeology) , paleontology , engineering , aerospace engineering
In insect wing polymorphism, morphs with fully developed, intermediate, and without wings are recognized. The morphs are interpreted as a trade‐off between flight and flightlessness; the benefits of flight are counterbalanced by the costs of development and the maintenance of wings and flight muscles. Such a trade‐off has been widely shown for reproductive and developmental parameters, and wing reduction is associated with species of stable habitats. However, in this context, the role of water locomotion performance has not been well explored. We chose seven water striders (Heteroptera: Gerridae) as a model to study this trade‐off and its relation to sexual conflicts, namely, Aquarius elongatus (Uhler), Aquarius paludum (Fabr.), Gerris insularis (Motschulsky), Gerris nepalensis Distant, Gerris latiabdominis Miyamoto, Metrocoris histrio (White), and Rhagadotarsus kraepelini Breddin. We estimated the locomotion performance as the legs’ stroke force, measured on tethered specimens placed on water with a force transducer attached to their backs. By dividing force by body weight, we made performance comparisons. We found a positive relationship between weight and force, and a negative one between weight and the force‐to‐weight ratio among species. The trade‐off between water and flight locomotion was manifested as differences in performance in terms of the force/weight ratio. However, the bias toward winged or wing‐reduced morphs was species dependent, and presumably related to habitat preference. Water strider species favouring a permanent habitat ( G. nepalensis ) showed higher performance in the apterous morph, but in those favouring temporary habitats ( A. paludum and R. kraepelini ) morphs’ performance did not differ significantly. Males had higher performance than females in all but three species studied (namely, A. elongatus , G. nepalensis , and R. kraepelini ); these three have a type II mating strategy with minimized mating struggle. We hypothesized that in type I mating system, in which males must struggle strongly to subdue the female, males should outperform females to copulate successfully. This was not necessarily true among males of species with type II mating.