The adaptive evolution of herbivory in freshwater systems
Results/Conclusions These hypotheses are based on basic ecological principles that many studies have examined in detail, and with a few assumptions, these ideas could be implemented into current research programs. For example, the intake-efficiency hypotheses might be tested using a similar experimental design to Alvarez and Peckarsky’s (2013). They measured growth rates of caddisflies and mayflies, algal accrual rates and per capita effects of grazers on algae in chambers that differed in the presence of moss and predation risk. They found no differences in growth; however, when mayflies were subjected to predation, algae associated with moss accrued at a slower rate, suggesting that they are using moss as both habitat and a source of food in the presence of predators. Comparable experiments could be designed to include additional life history trait estimates (e.g. herbivore survival) and estimates of foraging energy expenditure vs energy gain (as in optimal foraging theory).
Herbivory has been the focus of many ecological studies and these contributions have improved our understanding of animal diet ecology. However, there is a significant gap in knowledge pertaining to the adaptive evolution of herbivory in nature. The incorporation of these hypotheses to the current literature will provide information about diet evolution, where it is currently lacking. These proposed hypotheses represent a starting point that will lead to more comprehensive studies of diet evolution in freshwater and other systems.