Journal Article

The endangered <i>Iris atropurpurea</i> (Iridaceae) in Israel: honey-bees, night-sheltering male bees and female solitary bees as pollinators

Stella Watts, Yuval Sapir, Bosmat Segal and Amots Dafni

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 111, issue 3, pages 395-407
Published in print March 2013 | ISSN: 0305-7364
Published online December 2012 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcs292
The endangered Iris atropurpurea (Iridaceae) in Israel: honey-bees, night-sheltering male bees and female solitary bees as pollinators

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Background and Aims

The coastal plain of Israel hosts the last few remaining populations of the endemic Iris atropurpurea (Iridaceae), a Red List species of high conservation priority. The flowers offer no nectar reward. Here the role of night-sheltering male solitary bees, honey-bees and female solitary bees as pollinators of I. atropurpurea is documented.

Methods

Breeding system, floral longevity, stigma receptivity, visitation rates, pollen loads, pollen deposition and removal and fruit- and seed-set were investigated.

Key Results

The main wild pollinators of this plant are male eucerine bees, and to a lesser extent, but with the potential to transfer pollen, female solitary bees. Honey-bees were found to be frequent diurnal visitors; they removed large quantities of pollen and were as effective as male sheltering bees at pollinating this species. The low density of pollen carried by male solitary bees was attributed to grooming activities, pollen displacement when bees aggregated together in flowers and pollen depletion by honey-bees. In the population free of honey-bee hives, male bees carried significantly more pollen grains on their bodies. Results from pollen analysis and pollen deposited on stigmas suggest that inadequate pollination may be an important factor limiting fruit-set. In the presence of honey-bees, eucerine bees were low removal–low deposition pollinators, whereas honey-bees were high removal–low deposition pollinators, because they removed large amounts into corbiculae and deposited relatively little onto receptive stigmas.

Conclusions

Even though overall, both bee taxa were equally effective pollinators, we suggest that honey-bees have the potential to reduce the amount of pollen available for plant reproduction, and to reduce the amount of resources available to solitary bee communities. The results of this study have potential implications for the conservation of this highly endangered plant species if hives are permitted inside reserves, where the bulk of Oncocyclus iris species are protected.

Keywords: Endangered; Iris atropurpurea; pollination; pollinator effectiveness; Apis mellifera; night-sheltering; eucerine bees; solitary bees; pollen removal; pollen deposition; stigma receptivity; pollen viability

Journal Article.  8607 words.  Illustrated.

Subjects: Plant Reproduction and Propagation

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