Enhancing gardens as habitats for plant-associated invertebrates: should we plant native or exotic species?
Domestic gardens, typically consisting of a mixture of native and non-native plants, support biodiversity. The relative value of these native and non-native plants for invertebrates is largely unknown. To address this a replicated field experiment with plots planted with one of three assemblages of non-invasive perennial and shrubby garden plants (treatments), based on plant origin [UK native, near-native (Northern Hemisphere) and Exotic (Southern Hemisphere)] was established. Over 4 years the invertebrates were recorded by Vortis suction sampler and amount of plant material measured. The abundance of above ground plant-inhabiting invertebrates increased with canopy cover and was higher on the native treatment. For several functional groups including herbivores and some predatory groups the near-native plants supported only marginally fewer individuals compared to native plots, with exotic plants being less favoured. The experiment demonstrated that gardens and other cultivated ornamental plantings support a wide range of plant-inhabiting invertebrates from primary functional groups regardless of the plants’ origin and the more plant matter (canopy cover) available the greater the abundance. Greater abundance of invertebrates will be supported by gardens and cultivated planting schemes with plantings biased towards native and near-native plants and that provide dense vegetation cover. However, exotic plants should not be dismissed as these are inhabited by some invertebrates.
KeywordsCanopy cover Functional group Invertebrate abundance Invertebrate herbivore Invertebrate predator Ornamental plants
We would like to thank the project volunteers James Backshall, Crystal Duncan, Carolyn Hewitt, Helen Latham, Linda Moyes, Judi O’Prey, John Ricketts, Kathy Stones and Jenna Watt who maintained the plots and the members of RHS Wisley curatorial staff who assisted. Thanks are also due to those who provided help and advice including Jonty Denton, David Brooks, Suzanne Clark, Colin Crosbie, Victoria Coupland, Jim Gardiner, Gerard Clover, Alistair Griffiths, Andrew Halstead, Alison Haughton and Steve Head (the Wildlife Gardening Forum), David Notton, Juliet Osborne, Claire Ozanne, Laura Robins, Peter Shaw, Richard Sanford, Ian Waghorn and Roger Williams.
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