PATTERN AND PROCESS IN CO-EXISTENCE OF WATER-STRIDERS (HETEROPTERA: GERRIDAE)

SUMMARY (1) More species of water-striders colonized lakes each year than were reproductively successful. Reproductive success of common species could be predicted from proportion of various habitats present, but success of rare species was not predictable from any linear combination of five variables thought to influence gerrid population dynamics. Habitat diversity and gerrid species diversity were not correlated. (2) A dominant species, Gerris pingreensis, was able to exclude other species from bulrush habitats which were the most stable and favourable for growth of all species. The niche of G. pingreensis was included within that of G. buenoi and G. comatus; populations of the latter two species showed best reproductive success in non-bulrush habitats with emergent and floating vegetation, respectively, but occupied bulrush habitats in the absence of G. pingreensis. (3) Apparently few gerrid populations were in equilibrium which may account for the persistence of two rare species in central British Columbia. Under such conditions, strength of habitat preference seems to vary inversely with vagility of the species considered. SUMMARY (1) More species of water-striders colonized lakes each year than were reproductively successful. Reproductive success of common species could be predicted from proportion of various habitats present, but success of rare species was not predictable from any linear combination of five variables thought to influence gerrid population dynamics. Habitat diversity and gerrid species diversity were not correlated. (2) A dominant species, Gerris pingreensis, was able to exclude other species from bulrush habitats which were the most stable and favourable for growth of all species. The niche of G. pingreensis was included within that of G. buenoi and G. comatus; populations of the latter two species showed best reproductive success in non-bulrush habitats with emergent and floating vegetation, respectively, but occupied bulrush habitats in the absence of G. pingreensis. (3) Apparently few gerrid populations were in equilibrium which may account for the persistence of two rare species in central British Columbia. Under such conditions, strength of habitat preference seems to vary inversely with vagility of the species considered. SUMMARY (1) More species of water-striders colonized lakes each year than were reproductively successful. Reproductive success of common species could be predicted from proportion of various habitats present, but success of rare species was not predictable from any linear combination of five variables thought to influence gerrid population dynamics. Habitat diversity and gerrid species diversity were not correlated. (2) A dominant species, Gerris pingreensis, was able to exclude other species from bulrush habitats which were the most stable and favourable for growth of all species. The niche of G. pingreensis was included within that of G. buenoi and G. comatus; populations of the latter two species showed best reproductive success in non-bulrush habitats with emergent and floating vegetation, respectively, but occupied bulrush habitats in the absence of G. pingreensis. (3) Apparently few gerrid populations were in equilibrium which may account for the persistence of two rare species in central British Columbia. Under such conditions, strength of habitat preference seems to vary inversely with vagility of the species considered. SUMMARY (1) More species of water-striders colonized lakes each year than were reproductively successful. Reproductive success of common species could be predicted from proportion of various habitats present, but success of rare species was not predictable from any linear combination of five variables thought to influence gerrid population dynamics. Habitat diversity and gerrid species diversity were not correlated. (2) A dominant species, Gerris pingreensis, was able to exclude other species from bulrush habitats which were the most stable and favourable for growth of all species. The niche of G. pingreensis was included within that of G. buenoi and G. comatus; populations of the latter two species showed best reproductive success in non-bulrush habitats with emergent and floating vegetation, respectively, but occupied bulrush habitats in the absence of G. pingreensis. (3) Apparently few gerrid populations were in equilibrium which may account for the persistence of two rare species in central British Columbia. Under such conditions, strength of habitat preference seems to vary inversely with vagility of the species considered.