Gonzalo Rivas-Torres1,2,3,4, S. Luke Flory5, Chris Wilson5, Damian C. Adams6 and Bette Loiselle3,7
1Colegio de Ciencias Biológicas y Ambientales & Galapagos Academic Institute for the Arts and Sciences, Universidad San Francisco de Quito-USFQ, Ecuador
2Galapagos National Park scientific collaborator, Ecuador
3Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL 32611, USA
4Department of Geography, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
5Agronomy Department, University of Florida, Gainesville, FL 32611, USA
6School of Forest Resources and Conservation, University of Florida, FL 32611, USA
7Center for Latin American Studies, University of Florida, Gainesville, FL 32611, USA
Non-native invasive plants on islands may result in novel plant assemblages with unique abiotic characteristics. Despite the ecological and conservation implications of the appearance of such ecological novelties, few studies have evaluated how native and non-native plant species perform under these new environmental conditions. Here, we present among others, the results of an experiment to investigate how germination, establishment, and growth of native and non-native plant species are affected by the invasive canopy tree Cedrela odorata in the Galapagos. Cedrela was introduced for timber more than 70 years ago and now covers ~1,600 hectares that present unique abiotic and biotic conditions in one inhabited island of the archipelago. Although the species is economically important as a primary timber source, invasions are thought to have significant ecological consequences. To evaluate the effects of Cedrela on the performance of native and invasive plants, we established replicated plots across a block of Cedrela dominated forest sites and removed Cedrela canopy trees from half of all plots. We found that the establishment and growth of native tree species, including Scalesia pedunculata an endemic canopy-forming tree that co-dominated Cedrela infested areas, were positively affected by removal of the invasive tree. Although removing Cedrela benefited some important native species, this treatment also promoted increased growth and establishment of other problematic invasive plants. Additionally, our multiyear work showed that Cedrela invasive strategies are particularly interesting and diverse, ranging from shade tolerant and low herbivore pressure, to the use of chemicals to reduce endemic seedlings growth (including Scalesia) which is a recently discovered strategy for invasive plants on the Galapagos islands.
Here, we not only provide useful information regarding the performance of plants with different origins under novel conditions caused by dominant invasive plants, but also present an analysis of the suitable management actions which is based on ecological and socioeconomic data and this may assist forest restoration efforts in highly invaded areas in Galapagos and elsewhere.