• Scientists prove the positive contribution of human-introduced species by ecological substitution

    May 06, 2014

    The article, published in the prestigious Journal of Animal Ecology, proves that outsider birds, such as thrushes and blackbirds, contribute to the regeneration of autoctonous forests in New Zealand

    Tui (native species, on the left) and blackbird (exotic species, on the right), co-existing in a forest of New Zealand. Photo: Daniel Martínez.

    Foreign species may contribute positively in certain ecosystems, despite the traditional view that maintains that they pose a threat to the conservation of biodiversity. Scientists of the University of Oviedo, in collaboration with experts from the University of Canterbury in New Zealand, have proved that in the case of certain European bird, their contribution is positive through the effect of ecological substitution, since they assume the role of the battered local birds as spreaders of seeds in the native forests. This is the case of thrushes and blackbirds.

    The conclusions of the research conducted by Daniel García and Daniel Martínez, researchers from the Department of Biology of Organisms and Systems of the University of Oviedo, alongside Daniel Stouffer and Jason Tylianakis, from the University of Canterbury, has just been published in the prestigious Journal of Animal Ecology. The research project titled Redes ecológicas en peligro. Interacción plantas y flugívoros bajo el cambio global is sponsored by the Ministry of Economics and Competitiveness of Spain and the Royal Society of New Zealand.

    The general opinion maintains that foreign species always have a negative effect in ecosystems, since biological invasions may even cause local species to go extinct. Nevertheless, it has been proved that in ecosystems altered by humans, certain exotic species may be the only way to fill ecological vacuums left by extinct species.

    For four months, the researchers observed birds eating meaty fruits from native plants in the Northern and Southern Isles of New Zealand. This data was analyzed through an innovative technique that represents the ecological interactions between birds and plants in terms of social networks.

    In forests where blackbirds and thrushes are common, they prove capable of eating almost any fruit that they may find. This way, the majority of trees with meaty fruits, which are the most common variety in the forests of New Zealand, have their seeds spread wide, and they are helped to continue with their regeneration cycle, despite the decline of native spreading species. Without this foreign birds, many of these fruits would fall to the ground and their seeds would probably die after being attacked by fungi or predators.