Strong negative effect of alien herbivores on endemic legumes of the Canary pine forest

Abstract

We studied the effects of herbivores on populations of four endemic legume species in pine forests in Caldera de Taburiente National Park on La Palma, Canary Islands. Seeds of these species were sown in control and herbivore-exclusion plots. Over the subsequent 4-years period, we assessed the effects of herbivores by counting the number of individual plants that emerged and by following their growth. We assessed growth over time using three plant-size categories. For these four species, we conclude that the presence of herbivores, including barbary sheep (Ammotragus lervia), goat (Capra hircus) and European rabbit (Oryctolagus cuniculus), exerts a strong negative effect on plant establishment. We suggest that the paucity of understory plant species in the pine forests of the Canary Islands may be strongly correlated with the presence of introduced herbivores in this region. We propose urgent conservation measures, such as large fenced areas, control activities and the most effective measure, eradication.