Interactions between Native and Introduced Bees in New Zealand

There are about 40 species of native bees in New Zealand, all belonging to the two most primitive bee families. Seven species have been introduced and established, five of which belong to the most advanced family of bees. All bees exploit similar resources such as nest sites, pollen, and nectar, so the question arises as to whether native and introduced bees are competing for these resources. Similarly, are native or introduced bees affected by the pathogens of newly contacted bee species? Although basic data on many native bee species are scarce, wide differences in nest site requirements suggest that competition for nest sites does not occur, except for a slight overlap between large Hylaeinae and introduced Megachilinae. Many native bees and introduced honey bees forage on the same flowers, but honey bees from commercial hives, bumble bees, alkali bees and leafcutting bees forage primarily on introduced plants. Native bees frequently outnumber honey bees on native and some introduced plants. Peak native bee foraging occurs during the "honey flow" when pollen and nectar are abundant, thus competition between species for food is reduced. Leafcutting bees are attacked by native bee parasites but the converse is not known. It is concluded that some of man's activities such as destruction of native flowers, introduction of new flowers and unintentional creation of nest sites, have probably had more impact on native bees than any competition from introduced bee species. Some native bees have competed successfully with honey bees for about 140 years and for a lesser time with other introduced bee species, which suggests that competitive success should continue. The status of those native bee species which are uncommon cannot be estimated until basic biological data become available.