Does alary dimorphism imply dispersal dimorphism in the waterstrider, Gerris remigis?


Dr D. J. Fairbairn, Department of Biology, Concordia University, 1455 de Maisonneuve Blvd, W., Montreal, Quebec, Canada H3G 1M8.



  • 1The hypothesis that wing dimorphism reflects dimorphism for dispersal ability is tested in two populations of stream-dwelling waterstriders, Gerris remigis Say, in southern Quebec, Canada.
  • 2Movements were assessed directly by recaptures of marked adults, and indirectly by comparisons of residence times and patterns of disappearance of macropterous and apterous morphs. Sampling was done weekly, over a period of 26 months, and 4828 adult G.remigis were individually marked during this time.
  • 3Movements of >100 m were very rare for both morphs. The movement patterns of the two morphs were very similar, and differed only over the winter, when no macropters moved upstream. This latter observation suggests that macropters may be less successful than apterous individuals at moving overland, or rowing against a current at this time of year.
  • 4Residence times and patterns of disappearance of the two morphs were very similar during all seasons.
  • 5These results suggest that macropterous G.remigis do not, in general, disperse using any means unavailable to the apterous morph, and that macropters in this species should not be simply categorized as long-distance dispersers.