| EFFECTS OF TRIOPS NEWBERRYI (NOTOSTRACA: TRIOPSIDAE) ON AQUATIC INSECT COMMUNITIES IN PONDS IN THE COLORADO DESERT OF SOUTHERN CALIFORNIA |
WILLIAM E. WALTON A1
A1 Department of Entomology, University of California, Riverside, Riverside, California 92521, USA
The association between a size-selective floodwater predator, the tadpole shrimp Triops newberryi, and aspects of the aquatic insect community (successional pattern, size structure, and composition) were studied in replicate ponds in the Coachella Valley of southern California. The abundance of early colonists, particularly the mosquito Culex tarsalis, chironomid larvae, and mayfly nymphs, and the size structure of the aquatic insect communities in ponds containing tadpole shrimps differed significantly from ponds without shrimps. Based on headwidths of co-occurring aquatic insects, ponds containing tadpole shrimps at densities >5 individuals m2 had fewer small instars of aquatic insects relative to ponds without Triops. The composition of aquatic insect communities in ponds containing tadpole shrimps differed from ponds without Triops, particularly during the first 3 weeks after inundation. These results suggest that effects of tadpole shrimps, such as predation on early life history stages of co-occurring aquatic insects and possibly deterrence of oviposition by insects, were greatest for nematoceran dipterans and were comparatively small on groups that increase in abundance later in succession (corixids, mesoveliids, and notonectids). Triops is a generalist predator that lacks strong preferences for particular prey species, yet, can potentially have significant effects on the dynamics of aquatic insect communities in ephemeral habitats of arid regions.
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