Abstract. Acacia longifolia, a native legume from Australia, has been
introduced in many European countries and elsewhere, thus becoming one of the
most important global invasive species. In Europe, its flowering occurs in a
period unsuitable for insect activity: nonetheless it is considered
entomophilous. Floral traits of this species are puzzling: brightly coloured
and scented as liked by insects, but with abundant staminate
small-sized flowers and relatively small pollen grains, as it is common in
anemophilous species. Invasion processes are especially favoured when
reshaping local ecological networks, thus the interest in understanding
pollination syndromes associated with invasive plant species that may
facilitate invasiveness. Moreover, a striking difference exists between its
massive flowering and relatively poor seed set. We introduced a novel
approach: first, we consider the possibility that a part of the pollination
success is carried on by wind and, second, we weighted the ethological
perspective of the main pollinator. During the flowering season of A. longifolia (February–April 2016), we carried on exclusion experiments to
detect the relative contribution of insects and wind. While the exclusion
experiments corroborated the need for pollen vectors, we actually recorded a
low abundance of insects. The honeybee, known pollinator of acacias, was
relatively rare and not always productive in terms of successful visits. While wind
contributed to seed set, focal observations confirmed that honeybees transfer pollen when visiting both the inflorescences to collect pollen and
the extrafloral nectaries to collect nectar. The mixed pollination strategy
of A. longifolia may then be the basis of its success in invading
Portugal's windy coasts.
Pollination success in monochromic yellow populations of the rewardless orchid Dactylorhiza sambucina
