Fly with pollen visiting a parsnip umbel |
When plants
colonize new places they usually arrive without any of their natural enemies
and pollinators. The wild parsnip is native to Europe, as is its principal herbivore,
the parsnip webworm, a flower- feeding caterpillar. Both species have been accidentally
introduced into North America and New Zealand. In North America, wild parsnips first
appeared in the 17th century and parsnip webworms were accidentally introduced
approximately 250 years later. In contrast,
wild parsnips arrived in New Zealand in the mid-19th century and parsnip webworm arrived very recently,
in 2004. Pollinator attraction and herbivore defence are both mediated by
floral chemistry. Prior to the arrival of its major herbivore, wild parsnips in
New Zealand produced lower levels of chemical defences (volatiles). The goal of
our study was to determine whether, in the absence of their primary enemy, wild
parsnips in New Zealand are more attractive to pollinators.
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