| The existence of offshore island refuges in New Zealand that retain species which have been lost on the adjacent main North and South islands provides a unique opportunity to compare the functioning of ecosystem processes before and after species extinctions. Many endemic, flower-visiting, vertebrate species are locally extinct in the north of the North Island, but still occur on Little Barrier Island---an offshore island reserve. I quantified the importance of these vertebrate species as pollinators on Little Barrier Island, and assessed the consequences of the loss of these species on the adjacent North Island. I show that birds and bats are important pollinators in native forest systems, not just for flowers that specialize on bird pollinators, but also for more generalist flower species. I show that the endangered short-tailed bat (Mystacina tuberculata) is considerably more important as a pollinator than previously considered, and contributes more than birds to the pollination of some species. While bird-specialized plants like Alseuosmia macrophylla are highly pollen limited in the absence of endemic birds, recent-colonist birds and mammals (principally silvereyes, Zosterops lateralis, and invasive ship rats, Rattus rattus ) compensate for the loss of endemic pollinators in the case of three brush-inflorescence species, thus partially maintaining pollination function. |
