Village aliens: Self-seeding of indigenous and non-indigenous woody garden plants in a small desert village

Abstract

Garden plantings in rural villages can affect surrounding natural habitats if non-indigenous and extralimital plant species escape the gardens through dispersal and establishment. Escape from gardens initially occurs via self-seeding. We surveyed woody plant species in roadside gardens in the village of Prince Albert in the arid Karoo region of South Africa to establish which species were being planted and which were self-seeding. We classified plants by origin (non-indigenous, extralimital and locally indigenous and by dispersal structure and recorded microsites where seedlings occurred. Non-indigenous species dominated garden plantings (62% of 1081 individuals and 65% of 92 species) and included 30 legally regulated invasive species. Most (75%) non-indigenous species self-seeded, however 70% of self-seeded individuals were extralimital or locally indigenous species. The best predictor of self-seeding was planting intensity. Self-seeding occurred where supplementary water was available, and seedling density was greater in covered than open sites. Self-seeding did not differ between species with dry and fleshy fruits. The extralimital species Searsia pendulina was a prolific self-seeder and has potential to become invasive. Nurseries should promote locally indigenous plants or extra-limital species that do not self-seed, to reduce the risk of invasions into natural rangeland and riparian areas surrounding villages. [198 words]