Predator Chemicals Induce Changes in Mayfly Life History Traits: A Whole-Stream Manipulation

Abstract

In high‐elevation streams of western Colorado, mayflies (Baetis bicaudatus) develop faster, but mature at a smaller size where trout are present compared to streams where fish are absent. These life history traits reduce the time of larval exposure to trout predation, but cost reduced fecundity. We designed a field experiment involving manipulation of whole streams to determine whether these changes were caused by the presence of brook trout, and specifically, whether they could be triggered by trout chemical cues. In 1999 and 2000, we introduced water from containers with brook trout (Salvelinus fontinalis) into five naturally fishless streams, and fishless stream water into five adjacent control streams, to determine whether these cues alone could induce the mayfly life history traits we have observed in natural trout streams. As in previous small‐scale experiments, the size at which mayflies matured declined significantly in streams with added trout chemicals but did not change in streams with fishless water only. Thus, life history traits similar to those observed in the field were induced within the natural variability inherent in streams. These results demonstrate the strength of this predator–prey interaction and indicate that brook trout are an important agent of natural selection on mayfly life history traits.

Alarm substance from adult zebrafish alters early embryonic development in offspring

“…Such increased development rates in response to predation threat are common place (e.g. Tollrian 1995) but may have associated costs (Peckarsky et al 2002). Alternatively, the early occurrence of developmental events could relate to later physiological or behavioural traits, as has been demonstrated in tadpoles, which learnt to respond to novel predator cues following exposure as embryos (Mathis et al 2008).…”

Genetic contributions to the study of taxonomy, ecology, and evolution of mayflies (Ephemeroptera): review and future perspectives

“…They found no genetic differences associated with fish occurrence, a finding supported by experimental evidence that fish chemical cues can initiate such behaviour in Baetis originating from fishless streams (e.g. Peckarsky et al 2002). Robinson et al (1992) tested whether mayfly populations living in more variable habitats had greater genetic variation than those in more stable habitats.…”

Spawning salmon and the phenology of emergence in stream insects

“…(iii) Emergence may be a plastic response to increased risk (e.g. Peckarsky et al 2002), perhaps insects are responding to cues from salmon. Given that insects predominantly emerge prior to salmon entering the stream to spawn (figure 1), the cue would need to be from the previous year of spawners.…”