Insect seed predators and environmental change

1. The seed-to-seedling transition may be a critical stage in determining the dynamics of plant populations. Insects which kill seeds either before or after dispersal can influence the population dynamics of individual plant species, and ultimately, plant diversity and assemblage composition. 2. We discuss the potential for insect seed predators to maintain diversity in plant assemblages and to structure their composition, with a particular focus on diverse tropical forest habitats. We suggest that our ability to understand the functional effects of insect seed predators is hampered by a shortage of unbiased information on (i) their responses to the density of prey seeds at different spatial scales, and (ii) their host plant specificity. 3. Density-dependence and its implications may be best assessed using manipulative field experiments. Such approaches can reveal how insect seed predators respond behaviourally and demographically to the density of individual host species and multiple host species across a range of spatial scales. 4. Host specificity and its implications may be best addressed through quantitative food web approaches previously applied largely to host-parasitoid interactions. Food webs will allow ecologists to assess the likely importance of indirect interactions such as apparent competition and apparent mutualism in structuring plant assemblages, and the functional consequences of adding or removing individual resource or consumer species. 5. Fully quantifying the wider effects of seed predators will require studies that better integrate seed stage-specific demographic information, and which quantify the long-term effects of variations in seed predation rates for plant recruitment. 6. Synthesis and applications. Compared to other functionally important insect groups such as pollinators, seed predators have received relatively little attention in the context of the functioning and sustainability of agro-ecosystems and the consequences of global environmental change for ecological communities. A fuller understanding of the ecology of insect seed predator-plant interactions will be valuable to conservation and management in a range of natural and agricultural systems. For example, seed predator community ecology is relevant to predicting the consequences of deliberately or unintentionally introducing novel resource or consumer species; the process of habitat recovery following local disturbances; and managing the effects of pest or beneficial seed predators in agricultural crops. Furthermore, patterns of insect seed predation on a larger scale are likely to be highly sensitive to global environmental change drivers such as climate change and systematic habitat modification and fragmentation, with implications for the structure and organization of ecological communities more widely. © 2008 The Authors