DOI: 10.5061/dryad.54tm887
title: Data from: A test of trophic and functional island biogeography theory with the avifauna of a continental archipelago

description: 1. The classical MacArthur-Wilson theory of island biogeography (TIB)
 emphasizes the role of island area and isolation in determining island
 biotas, but is neutral with respect to species differences that could
 affect community assembly and persistence. Recent extensions of island
 biogeography theory address how functional differences among species may
 lead to non-random community assembly processes and different
 diversity-area scaling patterns. First, the trophic TIB considers how
 diversity scaling varies across trophic position in a community, with
 species at higher trophic levels being most strongly influenced by island
 area. Second, further extensions have predicted how trait distributions,
 and hence functional diversity, should scale with area. Trait-based theory
 predicts richness-corrected functional diversity should be low on small
 islands but converge to null on larger islands. Conversely, competitive
 assembly predicts high diversity on small islands converging to null with
 increasing size. 2. However, despite mounting interest in diversity-area
 relationships across different dimensions of diversity, these predictions
 derived from theory have not been extensively tested across taxa and
 island systems. 3. Here, we develop and test predictions of the trophic
 TIB and extensions to functional traits, by examining the diversity-area
 relationship across multiple trophic ranks and dimensions of avian
 biodiversity in the Ryūkyū archipelago of Japan. 4. We find evidence for a
 positive species- and phylogenetic diversity-area relationship, but
 functional diversity was not strongly affected by island area. Counter to
 the Trophic TIB, we found no differences in the slopes of species-area
 relationships among trophic ranks, although slopes varied among trophic
 guilds at the same rank. We revealed differential assembly of trophic
 ranks, with evidence of trait-based assembly of intermediate predators but
 otherwise neutral community assembly. 5. Our results suggest that niche
 space differs among trophic guilds of birds, but that differences are
 mostly not predicted by current extensions of island biogeography theory.
 Whilst predicted patterns do not fit the empirical data well in this case,
 the development of such theory provides a useful framework to analyse
 island patterns from new perspectives. The application of empirical
 datasets such as ours should help provide a basis for developing further
 iterations of island biogeography theory.
description: Bird biodiversity of the
 Ryukyu archipelagoFile describing the
 spatial properties of 32 ryukyu islands/island groups (coordinates and
 island size), and their bird biodiversity separated by groups. Landbirds
 refer to those living and foraging on land, whereas seabirds forage at sea
 (see supporting information). In each case diversity (species richness,
 functional diversity [MPD based on Wilman et al. trait database] and
 phylogenetic diversity [MPD based on Jetz et al. phylogeny]) is subset by
 trophic groups, including all landbird/seabird species, carnivores,
 insectivores, frugivores, granivores, omnivores and herbivores (which are
 frugivores and herbivores). Data are observed valeus only (not null
 distributions based on randomisations). See Methods of Ross et al. for
 further details.Ross et al.
 JAE_Dryad.xlsx