The habitat templet and life history strategies of pond skaters (Heteroptera: Gerridae): reproductive potential, phenology, and wing dimorphism

Abstract

Reproductive traits, diapause, and wing dimorphism of four pond skater species occurring in central Alberta, Canada, are explained as adaptive responses to a complex of habitat features. Species using temporary habitats had greater fecundity, but habitat permanence alone was a poor predictor of reproductive longevity, preoviposition period, or reproductive rate. Fecundity and longevity were significantly lower and more variable in direct than in diapaused breeders. There was no geographical or annual variation in fecundity, suggesting that values observed are good measures of reproductive potential. Overwintered females of species from temporary habitats (Gerris buenoi and Limnoporus dissortis) lived longer than those from more permanent habitats (G. comatus and G. pingreensis), and, concomitantly, are able to spread reproduction over several ponds. Proportion of summer-generation bugs breeding without diapause was inversely related to habitat permanence for the Gerris species, but few nondiapause breeders occurred in L. dissortis. Diapause was not averted consistently by exposure to increasing long-day photoperiods, and sensitive stage for diapause induction varied within all species. In G. pingreensis and L. dissortis many individuals reaching the adult and fifth instar by the solstice diapaused. Diapause and wing morphism were associated only loosely in the dimorphic species. Many apterous G. pingreensis entered diapause despite early emergence. Wing morph in G. pingreensis is determined genetically but is not based in simple Mendelian inheritance. Flightless bugs occur mainly among direct breeders in G. buenoi and G. comatus but many direct breeders were macropterous. Wing morph is influenced by a photoperiod switch in G. buenoi, but there is also genetic variation. There was no significant difference in total fecundity, longevity, or juvenile development time between wing morphs of the same generation in either G. buenoi or G. pingreensis. However, flightless females had shorter preoviposition periods, leading to greater egg production over the first 20 days of reproductive life. Gerrid life histories are adaptions to a complex of factors, including but not confined to habitat stability. Other aspects of the habitat templet such as the impact of natural enemies and food input should be considered.