›› 2013, Vol. 56 ›› Issue (3): 293-298.doi:

• RESEARCH PAPERS •

### Flower-visiting insect diversity of the alien plant Erigeron annuus (Asteraceae) in Nanjing, southeastern China and an analysis of factors influencing their foraging preference

1. （Key Laboratory of Integrated Management of Crop Diseases and Pests of Ministry of Education, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China）
• Online:2013-03-20 Published:2013-03-20

Abstract: To investigate the diversity of native insects visiting flowers of the alien plant Erigeron annuus (Asteraceae) and factors affecting flower-visiting preferences, a two-year field survey using a random sampling method was undertaken in the suburb of Nanjing, southeastern China, and the hurdle model was used to analyze environmental factors that influence foraging for and selection of flowers by estimating the acceptance probability (measuring whether the visitation happens or not) and the visit frequency (measuring the extent of visits if the visitation happens). The survey uncovered 145 species from 54 families in nine insect orders, among which Hymenoptera, Lepidoptera and Coleoptera were rich in number of families each accounting for 20.75% of all families, respectively, followed by Diptera (18.87%) and Hemiptera (13.21%). Diptera was the highest in species richness accounting for 26.39% of all species, followed by Hymenoptera (18.75%), Coleoptera (17.36%), and Lepidoptera (15.38%), respectively. The species richness of most insect orders was higher in June and July and less in September, with the exception of Diptera which had higher species richness in May.  The analysis of the influence of environmental factors on the acceptance probability and the visit frequency of the three most dominant insect orders, i.e., Hemiptera, Diptera and Hymenoptera, using the hurdle model showed that the factors affecting the tendency of hemipterans and hymenopterans to accept E. annuus flowers were more than those influencing their visit frequency, suggesting that in these insects multiple environmental clues may be required to make a behavioral decision for the acceptance of the flower but fewer factors for the visitation extent of the flower. Plant density influenced the acceptance probability of hemipterans and hymenopterans, while flower density affected the acceptance probability and the visit frequency of hemipterans and dipterans, suggesting that characteristics of E. annuus flowers may play an important role in the visiting behavioral decision in these groups of native insects.