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Effects of bird extinctions and introductions on the functional and taxonomic diversity of oceanic islands
Publication . Soares, Filipa Coutinho; Lima, Ricardo Faustino de; Palmeirim, Jorge Manuel Mestre Marques; Rodrigues, Ana Sofia Luís
Human activities are causing major changes in the composition of species communities worldwide. Oceanic islands are at the epicentre of these changes, being among the most threatened ecosystems. Drastic changes in island bird communities resulting from both species extinctions and introductions are likely to have important repercussions on the composition and function of island avifaunas, potentially causing severe knock-on effects on island ecosystems. The main objective of this thesis was to explore the taxonomic and functional implications of bird extinctions and introductions for the avifauna of oceanic islands worldwide. It focuses on large oceanic islands (> 100 km2; n = 74), distributed across three oceans. Using island lists of extinct and extant, native and introduced species, plus species functional traits and island characteristics, the thesis first addresses the potential competition between native and introduced island bird species. Then, it evaluates the impacts of bird extinctions and introductions on island functional diversity, investigating island-level consequences, taxonomic and functional homogenization among archipelagos, and patterns and drivers of spatial and temporal taxonomic and functional changes. Overall, the results suggest that marked niche differentiations between native and introduced birds explain the apparent rarity of competition-driven extinctions. Similarly, introduced birds differ from extinct birds because they mostly prefer human-modified landscapes, which might explain why they do not compensate for the lost functional diversity due to extinctions. Island bird assemblages are becoming functionally poorer because they are losing unique species while gaining widespread functionally more redundant species, and therefore are becoming taxonomically and functionally homogenized. Anthropogenic pressure and human connectivity are driving the taxonomic and functional changes across oceanic islands. Assessing temporal changes in taxonomic and functional diversity is key to understand anthropogenic impacts, predict future changes and propose effective conservation tools to safeguard the resilience of ecosystem functioning.
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Fundação para a Ciência e a Tecnologia
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PD/BD/140832/2018