Impact of Non-native Mammalian Herbivores on Insular Plant Communities in the Canary and Balearic Islands

Biological invasions are a major cause of loss of biodiversity worldwide, particularly on islands. Introduced mammalian herbivores are among the most threatening of all invasive species, especially goats [Capra hircus (Linnaeus, 1758)], sheep [Ovis orientalis aries (Linnaeus, 1758)], mouflon (Ovis orientalis musimon [Pallas, 1762)], Barbary sheep [Ammotragus lervia (Pallas, 1777)], and rabbits [Oryctolagus cuniculus (Linnaeus, 1758)]. The vulnerability of insular plant communities, especially the endemic flora, is strongly influenced by their historic (and present) herbivory context, within which these introduced herbivores have played a key role. The effects of the introduction of mammals such as goats and rabbits are difficult to elucidate, as their introductions occurred thousands (or hundreds) of years ago and data on the previous status of the plant communities are not available. However, the present-day impacts of both of these herbivores on insular plant communities have been intensively studied. Herbivory can reduce the distribution area and constrain insular endemic species to inaccessible areas such as cliffs or islets, which impoverishes the original insular ecosystems and changes their species composition. Moreover, the negative effects of these species on the insular native flora have led to the development of eradication and control programmes on many islands, with the aim to recover and protect native plants. Coordination between policymakers, managers, researchers, hunters and society is crucial in order to identify efficient solutions to protect and restore insular plant communities, effectively manage hunting activities and optimally limit the effects of introduced mammals.