Evolution of aquatic insect behaviours across a gradient of disturbance predictability

Abstract

Natural disturbance regimes-cycles of fire, flood, drought or other events-range from highly predictable (disturbances occur regularly in time or in concert with a proximate cue) to highly unpredictable. While theory predicts how populations should evolve under different degrees of disturbance predictability, there is little empirical evidence of how this occurs in nature. Here, we demonstrate local adaptation in populations of an aquatic insect occupying sites along a natural gradient of disturbance predictability, where predictability was defined as the ability of a proximate cue (rainfall) to signal a disturbance (flash flood). In controlled behavioural experiments, populations from predictable environments responded to rainfall events by quickly exiting the water and moving sufficiently far from the stream to escape flash floods. By contrast, populations from less predictable environments had longer response times and lower response rates, reflecting the uncertainty inherent to these environments. Analysis with signal detection theory showed that for 13 out of 15 populations, observed response times were an optimal compromise between the competing risks of abandoning versus remaining in the stream, mediated by the rainfall-flood correlation of the local environment. Our study provides the first demonstration that populations can evolve in response to differences in disturbance predictability, and provides evidence that populations can adapt to among-stream differences in flow regime.

Vulnerability of stream biota to climate change in mediterranean climate regions: a synthesis of ecological responses and conservation challenges

“…Organisms might not be able to adapt and respond by their resilience and resistance abilities to the new disturbance regimes resulting from climate change that surpass the intensity, frequency, or duration thresholds of natural disturbances (Lytle, 2007;Lytle et al, 2008). The ability of biota to cope with these disturbances is very poorly understood, which weakens the predictive accuracy of the ecological responses.…”

Interannual and seasonal variability of macroinvertebrates in monsoonal climate streams

“…Flow fluctuations and extreme conditions such as floods are primary sources of variability and disturbance (Cowell et al 2004). High discharge events can cause severe population losses and changes in the community composition and structure (Hart and Finelli 1999;Lytle et al 2008). Streams in monsoonal environments are subject to extreme seasonal variation in flow (Jacobsen and Encalada 1998;Brewin et al 2000).…”

17 novel polymorphic microsatellite markers for the giant water bug, Abedus herberti (Belostomatidae)

“…Extirpation of populations, possibly due to climate change and water withdrawals by humans, is ongoing and leads to significant ecosystem-level changes (Bogan and Lytle 2011). Its naturally fragmented distribution and conservation status have made A. herberti the subject of recent studies on phylogeography (Finn et al 2007), population stability (Finn et al 2009), and behavioral adaptations (Lytle et al 2008). Belostomatids are also interesting because males provide exclusive parental care, and A. herberti has become a model system for studying sperm competition (Smith 1979) and mating systems evolution (Smith 1997).…”