Deterministic assembly and anthropogenic extinctions drive convergence of island bird communities

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Triantis, Kostas, A | Rigal, François | Whittaker, Robert, J | Hume, Julian, P | Sheard, Catherine | Poursanidis, Dimitrios | Rolland, Jonathan | Sfenthourakis, Spyros | Matthews, Thomas, J | Thébaud, Christophe | Tobias, Joseph, A

Edité par CCSD ; Wiley -

International audience. Aim: Whether entire communities of organisms converge toward predictable structural properties under similar environmental conditions remains controversial. We tested for community convergence in birds by comparing the structure of oceanic archipelago assemblages to their respective regional species pools.Location: Eighteen major oceanic archipelagos of volcanic origin with global distributionMajor taxa studied: Terrestrial birdsMethods: We compiled a comprehensive database of morphological trait and phylogenetic data for 6,579 bird species, including species known to have become extinct due to human activities. We quantified morphological and phylogenetic dissimilarity among species between pairs of archipelagos, using a modified version of the mean nearest taxon distance. We tested for convergence by estimating whether overall mean turnover among archipelagos and pairwise turnover between archipelagos was lower than expected by chance.Results: For all land-birds, we found that turnover in body plan, body mass and phylogeny among archipelagos was significantly lower than expected. Seventeen (of 18) archipelagos showed significant body plan and phylogenetic similarity with at least one other archipelago. Similar convergent patterns of community assembly were detected in different subsamples of the data (extant species, endemics, native non-endemics, and Passeriformes only). Convergence was more pronounced for extant species than for extant and extinct species combined. Main conclusions: Consistent convergence in phylogenetic and morphological structure among archipelagic communities arises through a combination of non-random colonization and in situ adaptation. In addition, by including data from extinct taxa, we show that community convergence both precedes and is accentuated by the anthropogenic extinction of endemic lineages. Our results highlight the potential role of non-random extinction in generating patterns of community convergence and also show that convergence existed even prior to anthropogenic extinctions as a result of deterministic community assembly in similar environmental settings at the global scale.

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