Vacant niches help predict invasion risk by birds

• Autor(a) principal: González-del-Pliego, Pamela
• Data de Publicação: 2023
• Outros Autores: Mendoza, Manuel, Santana, Joana, Ribeiro, Joana, Reino, Luís, Araújo, Miguel B.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.5/31328
• topic: alien species; avian; trophic guilds; trophic structure; unsaturated communities; vacant niches

Aim: If communities have a ceiling determining the number of species that can coexist, then the ability of alien species to establish at any given location should be related to the quantity of vacant niches available. We developed a new approach to estimate the extent to which niches are vacant and then explored the relationship between vacant niches and alien species. Location: Global with focal tests in Europe and North America. Taxon: Birds. Methods: Drawing on a global classification of trophic structures for birds, we cal- culated a ‘vacant niche ratio’ metric to quantify the expected level of saturation (i.e. number of vacant niches) for each 1° × 1° grid cell globally, based on the difference between expected and observed numbers of bird species for all trophic guilds. Next, we used random forests to examine if the presence of plant-invertivore (whose food source represents plants, seeds, fruits and invertebrates) and granivore alien bird spe- cies was associated with the vacant niche ratio across well-sampled regions. Results: In Europe, we found a significant relationship between alien species and vacant niches, with greater numbers of alien species being found in communities that offered greater numbers of vacant niches overall, and across habitat types. In North America, we found no significant relationship between plant-invertivores and vacant niches, while for granivores, we found that areas with fewer vacant niches had greater numbers of alien species, especially in forests. However, vacant niches alone correctly predict 69% of the presence of alien bird species when combining both regions and trophic guilds. Main Conclusions: Most regions of the world have unsaturated bird communities, with the level of saturation in communities varying within regions and trophic guilds. We found that although often-neglected, vacant niches are likely to be, at least par- tially, related with the successful establishment of alien bird species.