Specialized relationships between animals and plants are the norm in nature rather than the exception and landscape designs that destroy them also degrade local ecosystem function. Plants that evolved in concert with local animals provide for their needs better than plants that evolved elsewhere. The most common and arguably most important specialized relationships are those that have developed between insect herbivores and their host plants. Here, I explain why this is so, why specialized food relationships determine the stability and complexity of the local food webs that support animal diversity, and why our yards and gardens are essential parts of the ecosystems that sustain us. I also discuss how we can use our residential and corporate landscapes to connect the isolated habitat fragments around us and produce valuable ecosystem services, and what we can do to make our landscapes living ecosystems once again.
Native plants are becoming widely used in built landscapes to help mitigate the loss of biodiversity caused by urbanization. The primary advantage of native plant species over introduced ornamentals is their ability to support the development of the insects that fuel vertebrate food webs as well as specialist pollinators. The horticultural industry has introduced many cultivars of native plants to improve their aesthetic value and disease resistance, but there has been little work that measures the impact of these genetic changes on insect herbivores and pollinators. Here we measure how six desirable traits in native woody plant cultivars (leaf color, variegation, fall color, habit, disease resistance, and fruit size) compare with their wild types in terms of their ability to support insect herbivore development, abundance, and species richness. Using a common garden experiment, we quantified the abundance and diversity of insect herbivores using each species and its cultivars for growth and development over a 2-year period, as well as cumulative feed damage over the entire season. We also conducted feeding tests with evergreen bagworm (Thyridopteryx ephemeraeformis) to measure the preference of hatchling caterpillars for cultivars vs. straight species. We found that cultivars that had leaves altered from green to red, blue, or purple deterred insect feeding in all three experiments, a preference for variegated cultivars in one of our three experiments, but no consistent pattern of use among the species and cultivars chosen for other traits. These results suggest that the usefulness of native cultivars in restoring insect-driven food webs depends on the cultivar trait that has been selected.