Management actions to mitigate the impacts of invasive plant species require knowledge
of the mechanisms influencing invasion success and anticipating interactions with
various control options. To meet this need, I examined the impacts of the invasive plant
Rubus niveus on the native communities of the Scalesia forest of Santa Cruz Island; its
competitive abilities compared to some native, woody, species; and, factors affecting the
invasion process. This knowledge was then used to evaluate and understand the failure of
a five year eradication attempt of R. niveus on Santiago Island. Increasing densities of R.
niveus had a negative effect on plant diversity and abundance also resulting in changes
of forest structure. Experimental plots were used to elucidate mechanisms of how it
displaced native species. Rubus niveus showed a faster growth rate and biomass
production than native woody species; it also had a vastly larger seed bank. Increasing
sunlight positively affected the growth, biomass production and reproduction of adult
plants whereas germination was optimal at intermediate light conditions. Conversely,
water stress affected mainly the performance of R. niveus whereas native species were
more resilient. Although increasing native canopy cover negatively affected density of R.
niveus, it still survived under low light conditions. The implication is that R. niveus
rapidly invades after individual tree-falls or stand dieback but also is capable of invading
undisturbed forest. After five years of intensive management of R. niveus in Santiago
Island eradication seems unlikely. The invasion area continues to expand because: a
failure to find all plants before they fruit, bird dispersal over long distance and the ability
to colonize undisturbed areas and outcompete native vegetation. Furthermore,
management actions have altered ecosystem processes. A more strategic paradigm in
needed for R. niveus in Galapagos.