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April 17, 2014

University of Canterbury researchers are investigating some positive features of animals being introduced to New Zealand.

Exotic animals are generally considered to be a major threat to native species in New Zealand and worldwide.

Despite numerous examples of invasive species harming eco-systems, exotic species may actually be able to fill ecological gaps in their new home, such as those left by native species that have become extinct.

University of Canterbury ecologist Professor Jason Tylianakis says no study has explicitly tested whether exotic species fill the roles left by declining native species.

“A collaborative research project between scientists at the University of Canterbury and the University of Oviedo, Spain, has examined the role of exotic birds in dispersing the seeds of native New Zealand trees and shrubs.

“Many fruiting plants require birds to carry their seeds to new locations and drive the persistence and recovery of native forests.

“New Zealand fruit-feeding birds have historically suffered a strong decline but the country has also gained new fruit-eaters in the form of introduced European birds, such as blackbirds and song thrushes.’’

The Canterbury researchers studied the network of feeding interactions between different species of plants and birds in the North and South islands. They found that the intermediate body and beak size of exotic birds allowed them to feed on a great variety of different fruits.

This allowed the birds to disperse seeds of plant species that were not eaten by native birds at any given location and helped to stabilise seed dispersal across a whole range of plants.

Without introduced species, many native plants would not have their fruits eaten and their seeds would simply fall to the ground below the tree.

Another Canterbury biological sciences researcher, Dr Daniel Stouffer, says exotic species were less discriminating in their fruit consumption patterns.

“Native fruit-eaters have developed strong affinities for or against consumption of native fruit species making our native communities vulnerable to loss of key bird species. However, the exotic species are more than happy to make equal use of all the fruits available, thereby spreading their benefit more widely.’’

Professor Tylianakis says people often consider invasions by non-native species as always being harmful.

“However, many of our native species have already become extinct and sometimes we need new species to fill their role. Although they often do harm, we can’t always assume that non-native species are the bad guys in our constantly changing eco-systems,” Professor Tylianakis says.

For further information contact Professor Jason Tylianakis, School of Biological Sciences, on 021 0436775 or Dr Daniel Stouffer on 02108258815 or UC Media Consultant Kip Brook on 0275030168.

Photo: Professor Jason Tylianakis.