James Russell Rounds up New Research on Island Invasives

James Russell explains findings from two newly released scientific papers that highlight the importance of biosecurity.

By: James Russell

Invasive alien species are the major threat to islands by most metrics, and two open access papers published recently highlight this threat in different ways. In Nature Ecology and Evolution Wayne Dawson and colleagues identify global hotspots of alien species richness, and find islands and coastal continental areas are most strongly invaded. They also determine taxonomic group pairings which occur disproportionately often, such as birds with mammals, or vascular plants with spiders. New Zealand is identified as a particular hotspot for all possible combinations of taxonomic group pairings.


Hotspot and coldspot regions for cross-taxon established alien species richness. Source: Nature Ecology & Evolution

Meanwhile, myself and colleagues from Island Conservation and the IUCN Invasive Species Specialist Group review invasive alien species on islands in Environmental Conservation. Analysing the distribution of invasive alien species on 33 small island developing states we found most invasive alien species are only on a few islands. However, we identify the 15 most widespread invasive alien species on islands. Most of these invasive alien species are plants, and outside of the tropical SIDS they are also widespread on other islands such as New Zealand. We also review the diverse impacts invasive alien species have on islands, and their interactions with other global change threats.

Species Name Type Origin
Leucaena leucocephala White leadtree Tree Central America
Casuarina equisetifolia Ironwood Tree SE Asia to Australia
Paratrechina longicornis Longhorn crazy ant Ant Tropical Africa
Rattus rattus Black rat Rodent India to SE Asia
Adenanthera pavonina Red bead tree Tree India to S China
Psidium guajava Common guava Tree Central America
Gliricidia sepium Quick stick Tree Central America
Kalanchoe pinnata Air plant Herb Madagascar
Tapinoma melanocephalum Ghost ant Ant Tropical Africa and Asia
Culex quinquefasciatus Southern house mosquito Mosquito Tropical Americas
Cyanthillium cinereum Little ironweed Herb Tropical Africa and Asia
Jatropha curcas Barbados nut Shrub Central America
Mus musculus House mouse Rodent Central Asia
Oreochromis mossambicus Tilapia Fish Southern Africa
Portulaca oleracea Purslane Herb Africa and Asia

Both studies highlight the factors which correlate with higher invasive and alien species richness on islands, namely gross domestic product (wealth), population size and density, and island area and coastline. Both studies also emphasise the important role biosecurity must play in slowing the rate of introductions, and eradications must play redressing the impacts of invasive alien species on islands.


Biosecurity for intercepting invasive alien species on islands. Source: Environmental Conservation

All these topics were covered in depth at the Island Invasives conference held this month in Scotland.

Featured Photo: Hazy Coastline on Antipodes Island, New Zealand. Credit: Island Conservation
This article was originally printed in National Geographic

About James Russell

Conservation biologist Dr. James Russell works throughout the world on remote islands and other sites to provide conservation solutions by applying a combination of scientific methods. Based out of Auckland, New Zealand, from 2015 to 2017 he is also working on a Scientist without Frontiers programme in Brazil.

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