Species introductions shift seed dispersal potential more than extinctions across 120 island plant–frugivore communities
Abstract
Oceanic islands are hotspots of both species extinctions and introductions, which led to marked changes in species composition. This may disrupt key ecological interactions, such as animal-mediated seed dispersal, with potential long-term impacts on ecosystem structure and functioning. While some recent studies on individual taxa and islands report functional shifts, there has been no globally comprehensive study of how these changes vary in intensity and direction across islands. Importantly, it remains unclear how changes in traits of animal communities actually translate to ecologically relevant mismatches with native plant species. We report widespread functional remodeling of frugivore communities based on frugivory-specific traits of all native, extinct, and introduced vertebrate frugivores (birds, mammals, reptiles) from 120 islands in 22 archipelagos. There is a trend for taxonomic and functional substitution, mainly of nonvolant terrestrial mammalian omnivores replacing large-gaped flying frugivores, which caused a mismatch between gape size and seed size. This shift in seed dispersal potential risks underestimation in single-taxon studies. Overall, vertebrate introductions outnumbered extinctions both in terms of species (44 vs. 23%) and islands affected (92 vs. 76%). Moreover, introductions have driven stronger shifts in frugivore trait space compared to extinctions. However, the general patterns are modulated by substantial spatial variation and idiosyncratic functional shifts within frugivore communities on some islands. This, coupled with differences in plant seed size distributions, leads to variability in realized functional mismatches among islands. These results emphasize challenges with predicting functional responses to anthropogenic activities, while highlighting that remodeling of ecosystem interactions is a global concern.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (30)
Julia H. Heinen
Center for Macroecology, Evolution and Climate, Globe Institute, University of Copenhagen
Donald R. Drake
School of Life Sciences, University of Hawai’i at Mānoa
Kim McConkey
School of Geography, University of Nottingham Malaysia Campus
Julian P. Hume
Bird Group, Life Sciences Department, Natural History Museum
Sébastien Albert
UMR Peuplements Végétaux et Bio-agresseurs en Milieu Tropical
Haruko Ando
National Institute for Environmental Studies
Cláudia Baider
Instituto de Biociências, Dept. Ecologia, Universidade de Sao Paulo
Peter J. Bellingham
Manaaki Whenua—Landcare Research
Samuel B. Case
Department of Biology, University of Washington
Charles G. Chimera
Botany Department, University of Hawai’i at Mānoa
F. B. Vincent Florens
Tropical Island Biodiversity, Ecology and Conservation Pole of Research, University of Mauritius
Evan C. Fricke
Department of Civil and Environmental Engineering, School of Engineering, Massachusetts Institute of Technology
Ann Marie Gawel
Center for Biodiversity and Conservation, American Museum of Natural History, New York, NY, USA.
Aarón González-Castro
Department of Animal Biology, Edaphology and Geology, University of La Laguna
Ruben Heleno
Centre for Functional Ecology, Associate Laboratory TERRA, Department of Life Sciences, University of Coimbra
Sandra Hervias-Parejo
Centre for Functional Ecology, Associate Laboratory TERRA, Department of Life Sciences, University of Coimbra
Amy Hruska
School of Life Sciences, University of Hawai’i at Mānoa
Clyde T. Imada
Bernice Pauahi Bishop Museum, Honolulu
Ricardo F. de Lima
Center for Ecology, Evolution and Environmental Changes, Global Change and Sustainability Institute and Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa
Manuel Nogales
Island Ecology and Evolution Research Group, Instituto de Productos Naturales y Agrobiología, Spanish National Research Council
Haldre S. Rogers
Department of Ecology, Evolution, and Organismal Biology, Iowa State University
Beatriz Rumeu
Departamento de Biología, Instituto Universitario de Investigación Marina, Universidad de Cádiz
Dominique Strasberg
UMR Peuplements Végétaux et Bio-agresseurs en Milieu Tropical
Anna Traveset
Mediterranean Institute of Advanced Studies, Spanish National Research Council, University of the Balearic Islands, Esporles 07190, Mallorca, Balearic Islands, Spain
Alfredo Valido
Island Ecology and Evolution Research Group, Instituto de Productos Naturales y Agrobiología, Spanish National Research Council
Kenta Watanabe
National Institute of Technology, Okinawa College
Debra Wotton
Moa’s Ark Research
Tetsuro Yoshikawa
Graduate School of Science, Osaka Metropolitan University
Carsten Rahbek
Michael K. Borregaard
Section for Biodiversity, Globe Institute, University of Copenhagen