Free access
Volume 35, Number 6, November-December 2004
Page(s) 575 - 585
Apidologie 35 (2004) 575-585
DOI: 10.1051/apido:2004055

Foraging behavior and pollinating effectiveness of Osmia cornuta (Hymenoptera: Megachilidae) and Apis mellifera (Hymenoptera: Apidae) on "Comice" pear

Víctor H. Monzóna, b, Jordi Boschc, b and Javier Retanab

a  Laboratorio de Inmunología y Genética Molecular, Instituto de Biología, Universidad Católica de Valparaíso, Chile
b  Unitat d'Ecologia, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
c  Biology Department, Utah State University, Logan, UT 84322-5310, USA

(Received 3 April 2003; revised 20 January 2004; accepted 5 February 2004)

Abstract - We studied the pollinating effectiveness of Osmia cornuta and Apis mellifera on 'Comice' pear. Osmia cornuta visited more flowers per minute (13.8) than A. mellifera (7.1-9.8). Both species visited similar numbers of flowers per tree (6.7-7.9), and switched rows with similar frequency (4.0-7.9%). Rate of stigma contact was 98.7% for O. cornuta, 51.8% for A. mellifera pollen-nectar foragers, and 19.0% for A. mellifera nectar foragers. Fruit-set in flowers visited once was 28.9, 29.3, and 12.9%, respectively. Seed-set was similar (7-8 seeds per fruit) in all three types of flowers. Osmia cornuta females provisioned their nests with 94.4% pear pollen. Stepwise multiple regression showed that fruitlet-set across the orchard was mostly related to tree size (trees with fewer flowers set more fruit per flower) ( $\beta$ = -0.64; < 0.001), whereas seed-set at harvest was best explained by O. cornuta ( $\beta$ = 0.47; < 0.005) and A. mellifera ( $\beta$ = 0.35; < 0.05) spatial distribution.

Key words: Osmia cornuta / Apis mellifera / pollinating effectiveness / pear pollination

Corresponding author: Jordi Bosch

© INRA, EDP Sciences, DIB, AGIB 2004