Rubus niveus has become one of the most problematic and widespread invasive alien species in the Galápagos Islands in the last two decades. The Scalesia forests in the humid zones of the inhabited islands are already under high anthropogenic pressure and the expanding Rubus is threatening the last Scalesia remnants. In this study we investigated the effects of Rubus eradication measures on a number of vegetation parameters (vegetation cover, vegetation height, plant species richness and composition) as well as arthropod species richness, abundance and composition in three stages of Rubus control: recently controlled (C1), controlled three years ago (C3) and without control (SC). Matching our prediction plant species richness and vegetation cover, understory arthropod species richness and abundance as well as moss spider abundance were much lower in C1 compared to C3 and SC, whereas vegetation height was highest in SC. Contrary to our predictions arthropod abundance and species richness was not highest in C3 but rather similar to SC. Unexpected results were low canopy arthropod abundances in SC probably due to low canopy connectivity compared to C1 and C3 and very low abundances of endemic spiders in SC compared to C3 which might be explained by hábitat modifications through Rubus. The three sampled habitats were characterized by partly distinct species assemblages. Hence, for the conservation of arthropod diversity in the remaining Scalesia forest it could be profitable to manage Rubus with a rotating scheme resulting in a mosaic of sites with different Rubus cover.
For future research we suggest the implementation of mid- to long-term monitoring to observe shifts in species composition and to further evaluate the ongoing impacts of invasive plants and control measures on the Scalesia forests and its associated arthropod assemblages.

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