FNZ 57 - Apoidea (Insecta: Hymenoptera) - Environmental impacts
Donovan, BJ 2007. Apoidea (Insecta: Hymenoptera). Fauna of New Zealand 57, 295 pages.
(
ISSN 0111-5383 (print),
;
no.
57.
ISBN 978-0-478-09389-6 (print),
).
Published 07 Sep 2007
ZooBank: http://zoobank.org/References/B2070E05-13B6-4CBF-9A0A-0ACE40FA4796
Environmental impacts of introduced bees
Whether imported bees, and especially the honey bee, are impacting adversely on native bees because of possible competition for similar resources such as pollen and nectar, was examined by Donovan (1980). Although there is overlap in flower-visiting preferences, peak native bee foraging occurs during the ‘honey flow’ when pollen and nectar are abundant. It was concluded (in the absence of specific data) that many of man’s activities such as the destruction of native flora, the introduction of new flowers, and unintentional creation of nest sites have probably had more impact on native bees, both positive and negative, than competition from introduced bees, and that because some native bee species have the ability to outnumber honey bees and bumble bees after about 140 years of contact (now 167 years for honey bees) they are enjoying considerable competitive success.
However, this study has found that 4 species of native bees are known from very few specimens; Leioproctus otautahi (1 male), L. nunui (2 females, 4 males), Hylaeus matamoko (18 females, 3 males), and H. murihiku (2 males). As mentioned elsewhere whether L. otautahi is truly native is uncertain, but the lack of more specimens since the collection of just a male 46 years ago from Christchurch, MC, where the environment is being increasingly urbanised may indicate the species is extinct. Because H. murihiku is known from only 2 specimens from Secretary I., FD, its conservation status must be in doubt, but of course there has been minimal collecting in such a remote locality. More collecting will probably reveal that the remaining 2 species will be more widespread and abundant than known at present. Whether imported bees have impacted adversely on the population size and distribution of these 4 species is unknown.
Since the discovery of the honey bee mite Varroa destructor in beehives near Auckland, AK, in early 2000, the whole North Island and Great Barrier Island have been colonised, with anecdotal reports that nearly all feral colonies have been killed, as well as many managed hives. This reduction in the number of foraging honey bees will reduce any competitive pressure on North Island native bees for pollen and nectar. The discovery of the mite in beehives at Nelson NN in June 2006 means that South Island native bees will soon also benefit. Because the mite is specific to honey bees, it will not impact adversely on other species of bees.
The occurrence in New Zealand of 5 species of bees from Australia: the indigenous Lasioglossum cognatum, and the adventive Hylaeus asperithorax, H. perhumilis, Hyleoides concinna, and Euryglossina proctotrypoides, and also Anthidium manicatum which originated from Europe, suggests that more species of bees are likely to reach New Zealand, despite the efforts of MAF Biosecurity to protect New Zealand from unwanted organisms. Tube-nesting species which might make nests in holes and cracks in packing crates, etc., rather than ground-nesting species, are the most likely candidates for immigration. It is instructive that all 5 adventive species are tube- or cavity-nesters.
Another possible source of new species of bees is the purposeful/deliberate importation of species that are specialist pollinators of certain crops, as suggested by Donovan (1990). However, since the establishment of the Environmental Risk Management Authority, the financial costs of applying for permission to import are so great that there have been no proposals to do so. In the foreseeable future, New Zealand’s native bees are therefore unlikely to face competition from purposely imported species of bees.
The possible impact of introduced bees on other native biota has not been considered, but the removal from the native ecosystem of great quantities of pollen, nectar, and honeydew throughout the year by the honey bee in particular must give cause for concern. However, Butz Huryn (1995) found that the few plant species with specialised plant/pollinator relationships are abundant, with the exception of kaka beak Clianthus puniceus. Indeed, if honey bees have caused a reduction in some native biota that are pollinators, it is possible they have at least partly replaced them as pollinators. By occupying cavities in trees, honey bees may displace cavity-nesting birds and other organisms.