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Disturbance to a stream food web by a bacterial larvicide specific to black flies: feeding responses of predatory macroinvertebrates
Author(s) -
WIPFLI MARK S.,
MERRITT RICHARD W.
Publication year - 1994
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.1994.tb00869.x
Subject(s) - black fly , predation , biology , odonata , nymph , simulium , baetidae , mayfly , ecology , larva , invertebrate , libellulidae , zoology , dragonfly
SUMMARY 1. A field study was conducted to: (i) assess feeding habit changes of two predatory stoneflies following the loss of larval black fly (Diptera: Simuliidae) prey from two streams; and (ii) determine the relative importance of black fly larvae as prey for these and other selected predatory benthic macroinvertebrates. 2. Acroneuria lycorias and Paragnetina media (Plecoptera: Perlidae) diets were monitored in response to local reductions in larval black fly populations caused by Bacillus thuringiensis var. israelensis ( B.t.i. ) in two Michigan streams. These predators were collected from B.t.i. ‐treated and control sections of the streams, and their foreguts inspected for prey. 3. Black flies were the major dietary component of both predators collected from the control sections, but the number of black flies ingested was significantly less for predators collected from B.t.i. ‐treated habitats. Total number of prey ingested significantly decreased for A. lycorias , but not for P. media , and non‐black fly prey consumption significantly increased for P. media , but not for A, lycorias , following B.t.i. applications. 4. In prey choice trials conducted in experimental channels, A. lycorias and P. media showed no preference between prey types (black flies and mayflies). Body mass gain of individual A. lycorias nymphs was measured, and was similar for nymphs in black fly‐rich and black fly‐poor environments. Conversely, Isoperla signata and I. dicala (Plecoptera: Perlodidae) ingested significantly more Simulium vittatum (Diptera: Simuliidae) than Baetis flavistriga (Ephemeroptera: Baetidae) or Epeorus vitrea (Heptageniidae) prey. Boyeria vinosa (Odonata: Aeshnidae) ingested significantly more B. flavistriga than S. vittatum prey. 5. Reducing black fly densities in these streams, using B.t.i. , indirectly and differentially affected predators. In black fly‐poor environments, feeding habits of specialist predators were most affected, and generalist predators least affected because the latter consumed alternative prey. Predator—predator and predator‐prey interactions, and prey community structure may be affected indirectly by disturbances such as B.t.i. applications by reducing food resources and forcing predation onto less preferred prey.