The impact of introduced flowering species on alpine plant-pollinator networks in southern New Zealand

Christa Miller *1, Katharine Dickinson 1, Barbara Barratt 2, Janice Lord 1

1 University of Otago
2 University of Otago, AgResearch

Eligible for student prize

Introduced and native flowering plants compete not only for abiotic resources, but can also compete for insect pollinators. New Zealand's flora comprises approximately 50% introduced flowering plant species and many have established in alpine and montane areas forming novel communities along with introduced pollinating insects. Although insect pollination in alpine New Zealand is poorly understood, the few studies carried out to date reveal that native alpine New Zealand flowering plants are usually dependent on pollen vectors for successful reproduction. Non-indigenous pollinating insects and flowering species that integrate into native plant-pollinator webs could have a detrimental effect on native alpine plant-pollinator relationships. This study explores the impact of introduced plant and pollinating insect species on native plant-pollinator relationships in alpine southern New Zealand. Observations of insect visits to both native and introduced flowers along an altitudinal gradient were undertaken over the course of two years in addition to experimental flower arrays to compare insect choices between native and introduced flowers. Insect flower visitors were netted and pollen was collected from their bodies. Results indicated that native and introduced insects preferred introduced flowers, particularly Hypochaeris radicata. Pollen samples taken from insect flower visitors also confirmed that most insects visited introduced flowers. Such insect preferences for introduced flowers could have an adverse impact on the reproductive success of native flowering species whilst enhancing the spread of weedy non-native species. Conversely, introduced flower species could be supporting increased numbers of native insects.

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