Pollination ecology of the New Zealand alpine flora

The interactions between flowers and the insects that pollinate them have fascinated scientists for more than 200 years. The last century saw the establishment of the fundamental concept of pollination syndromes which allows classification of flowers according to the agents that pollinate them demonstrating specialisation and co-evolution of plants and pollinators. This concept has recently been questioned and the contrary, ubiquitous generalisation and chance have been proposed to be the driving forces behind plant – pollinator interactions on an individual and community level. The present study was carried out to address the question of the level of pollinator dependence and generalisation in pollination systems in an alpine plant community in alpine New Zealand. Initial research in New Zealand alpine habitats had lead to the assumption of minor importance of insect pollination as the alpine flora in New Zealand in general is not very conspicuous and the available potential insect pollinators are mainly flies and short-tongued native bees. Therefore it had been proposed that the level of autogamy and generalisation in pollination interactions in a high-alpine habitat should be high. However, it could be demonstrated that the majority of the 23 plant species in the alpine community depend on pollinator service to achieve reproductive success. A total of 87% of plant species under investigation are at least in part self-incompatible and therefore rely on pollinator service for outcross-pollen delivery. Moreover, it could be shown that the pollinators that transfer pollen do not choose plants at random. The pollination systems in the alpine community proved to consist of both rather specialised and rather generalised functional pollinator groups, moths and native bees belonging to the former and syrphid flies belonging to the latter. Furthermore, there was strong evidence that flower visitors do not automatically equal pollinators and that pollination efficiency differed between functional groups. When assessing the floral cues, e.g. flower colour and scent that attract a certain functional pollinator group, no clustering of the attractants in correlation with pollinator group could be demonstrated. However, the individual combination of colour and scent rendered each plant species distinct from most others. This novel feature of the alpine plant community may be interpreted as a way to facilitate associative pollinator learning. A foraging pollinator can easily memorise distinct flowers and subsequently proceed to direct visitation to repeat the experience of rewards. This way flower constancy and increased efficiency of pollen transfer is promoted allowing plants to benefit from adequate pollen delivery and xenogamous reproduction resulting in genetically diverse progeny that has a greater potential of survival in the challenging alpine environment