Personnel: Jill Lancaster (Project Leader) and Barbara Downes
Understanding the factors that limit population size is a challenging problem of widespread interest among ecologists, and of vital importance to sound practice in conservation and environmental management. Traditionally, freshwater ecologists have focused on the aquatic, juvenile stages of insects, with considerably less attention devoted to the transition stages between the aquatic juveniles and terrestrial adults. We concentrated on the recruitment of eggs from the terrestrial into the aquatic medium and the conversion of those eggs into neonates. Simply finding a suitable location to lay eggs may limit population size. Many stream insects lay their eggs on the underside of stream rocks that are emergent from the water’s surface and the supply of emergent rocks can limit egg recruitment. Once the eggs hatch, the mobility of neonates will dictate whether or how long any localised effects of emergent rock limitation persist and, by measuring neonate movement, we can identify the spatial scale relevant to studies about population dynamics. Thus, our research identifies whether bottlenecks occur for egg and neonate life history stages, how strong those bottlenecks might be, and the spatial scales at which the restrictions occur.