Insect diversity in our gardens

If you think about it, you're driving around the suburban environment, and every time a new development goes in, you have a lot of decision making happening as to what plant species are going to be planted around those properties. If we do all that landscaping with non-native plants, are we limiting the wildlife and conservation support system that could be available within that given plot of land? What the gardens we constructed for the study are trying to replicate are landscaping decisions that people might make if they wanted to support native insect communities that in turn support much of the diversity around us.

Researchers of the University of Delaware tried to understand how the composition of the plants that homeowners plant in their yards affects herbivore communities. To conduct the study, they planted imitation yards with different common gardens of both native and non-native tree species and collected data over a three-year period, determining the herbivore communities and species found on those plants. They compared native trees to non-native trees that had no close native relative and to non-natives that are closely related to the native community.

Within the distantly related group, they found that herbivores were less diverse when they looked at individual non-native tree species, and as they moved from one non-native tree species to another, they found similar species of herbivores using those trees. Non-native plants reduced the diversity of insect populations in gardens, even when these non-native plants are closely related to the native plants.

You get this compounding effect where you have a lower diversity of herbivores per tree but then you also are getting more similar species as you move between trees species and among sites, so you end up with even less diverse communities than you would expect. There is this group of species of non-natives that do not have any close native relatives at all. These non-natives support more generalized and redundant herbivore communities than the native plants that they're potentially replacing on landscapes.