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Exotic honeybees are the only effective pollinators of a temperate mangrove

By: Dr David Britton, Category: Science, Date: 20 Nov 2013

Honeybees were introduced shortly after European settlement and now appear to be the only effective pollinators of a native plant species.

Exotic honeybees are the only effective pollinators of a temperate mangrove

Tyge Hermansen © University of Wollongong

A few years ago I was approached by Tyge Hermansen, a postgraduate student based at University of Wollongong. He had been making extensive observations on pollinators visiting flowering Avicennia marina, one of two mangrove species found around Sydney.

He was trying to determine what organisms were the key pollinators of the mangroves, especially in urban areas where they are now isolated from other patches of native vegetation. He needed assistance identifying insects that he caught while making these observations, both through Museum staff and associates, and from comparison against our collection.

As we went through his samples he started talking about his observation that very few of the insects collected at the flowers were transferring any pollen at all, and the vast majority of the insects that did move pollen between flowers in a way that resulted in pollination were introduced honeybees, Apis mellifera.

I was extremely sceptical that the only effective pollinators were honey bees. Had he overlooked a native species of insect because of his survey methods? Had he considered that there might be nocturnal pollination by moths? Was his site selection at fault? Tyge patiently explained his methodology and I was left with no option but to accept that we had a native plant species that appeared to be solely pollinated by an introduced insect species.

The upshot of these discussions and identifications was that Tyge included me as a co-author on his paper, and successfully published it in the journal Estuaries and Coasts. Hopefully this finding will arouse the curiosity of other researchers, as we all want to know the identity of the original native pollinators, and whether they are still active elsewhere in the extensive natural range of the mangrove. Tyge has returned home to his native Denmark, so the problem remains for someone else to tackle.

More information:

Hermansen, T.D., Britton, D.R., Ayre, D.J. and Minchinton, T.E. 2013. Identifying the real pollinators? Exotic honeybees are the dominant flower visitors and only effective pollinators of Avicennia marina in Australian temperate mangroves. Estuaries and Coasts (online access)