Neighbourhood affects a plant’s risk of herbivory and subsequent success

Abstract

1. It is generally assumed that growing in proximity to sources of nectar will benefit plants by attracting predators and parasites that reduce herbivore loads.2. This paper documents patterns of hornworm Manduca quinquemaculata abundance on wild tobacco plants Nicotiana attenuata. Observations suggested that several plant traits were associated with hornworm eggs and larvae.3. Hornworms were more likely to be found on large tobacco plants.4. Hornworms were more likely to be found on tobacco plants with flowering Eriastrum densifolium neighbours.5. Experimental removal of neighbouring Eriastrum densifolium flowers or whole plants reduced hornworm damage to tobacco plants in neighbourhoods with E. densifolium. The effects of these manipulations were not found to increase reproductive success of neighbouring tobacco plants, although tobacco reproduction was reduced where M. quinquemaculata was abundant.6. These results suggest that close proximity to nectar resources could decrease plant fitness.