Within plant populations, species interactions may affect population establishment and persistence. Nursery pollination is a unique plant-insect interaction in which flowers are used as brood sites for the pollinator’s developing young, and in some nursery pollination systems, non-seed predator copollinators may be present. The specificity of nursery pollinators on their host plants may result in higher efficiency host searching and therefore increased pollination services (compared to copollinators), or higher nursery pollinator abundance may result in higher seed predation rates for the few plants in small populations. If nursery pollinators visit plants in small, isolated populations frequently without higher seed predation levels, the interaction will have a positive outcome and can be classified as a mutualism. In 2008, potted Silene stellata plants were used to establish two small, isolated populations with an additional potted plant group within the large, main population. These groups were monitored with camcorders and personal observations to document moth pollinator visitors. Flowers were collected for pollen deposition after examination for oviposition. In 2009, individual potted plants were placed in isolation and within the main population. Fruits were collected from these plants to determine rates of predation and fruit and seed set.
Results/Conclusions
In 2008, nursery pollinator (Hadena ectypa) visitation was higher in the natural population than the small, isolated populations, and copollinator visitation was extremely low in natural and isolated populations. Pollen deposition was significantly lower in the isolated populations. In the isolated populations, there were significantly fewer eggs laid per flower compared to the natural population. In 2009 visitation by H. ectypa was similar between isolated and main population plants, but copollinator visitation was significantly lower than H. ectypa in both main and isolated populations. Data from 2009 indicate that predation level was similar across the three populations, although oviposition rates taken in the field were higher on potted plants in the main population. Fruit and seed set also were higher on potted plants in the main population. These results indicate that in small, isolated populations nursery pollinators may be important despite lower pollen deposition since their visitation rates are higher than those of copollinators. Lower oviposition rates did not result in lower predation rates on isolated plants indicating that H. ectypa may have a large detrimental effect on population establishment despite the pollination services it provides to isolated S. stellata plants.
