The effects of land‐use dynamics on avian phylogenetic diversity across island ecosystems

Aim

To test whether forest extent and recent forest-cover change are associated with avian phylogenetic diversity and community-level evolutionary value across islands.

Location

Seven islands spanning Borneo and Wallacea in the Malay Archipelago.

Taxon

Terrestrial birds.

Methods

We sampled 1410 sites (2010–2022). We calculated phylogenetic diversity (PD), mean phylogenetic distance (MPD), mean nearest taxon distance (MNTD) and their standardised effect sizes (SES), as well as community-level EDGE (Evolutionarily Distinct and Globally Endangered). Responses to (i) average forest proportion (250-m radius) and (ii) recent forest-cover change were analysed with spatial linear mixed-effects.

Results

Observed PD showed a negative visual trend with increasing forest proportion, whereas SES PD declined. MPD showed only a weak positive visual trend with forest proportion, whereas SES MPD showed no clear response. Although observed MNTD appeared to increase in the binned visual summaries, both observed MNTD and SES MNTD showed significant negative associations with forest cover in the spatial models, indicating stronger nearest-neighbour phylogenetic clustering in more forested sites. Effects of recent forest loss (2010–2022) on SES metrics were generally weak and inconsistent. Although PD also declined with decreasing rates of forest change, community-level EDGE was higher where forest cover was greater, indicating higher average evolutionary distinctiveness and extinction risk.

Main Conclusions

In this archipelagic system, forest amount is a key correlate of phylogenetic structure and the retention of evolutionarily distinctive, high-risk lineages. By contrast, recent forest-cover change showed weaker and more context-dependent associations. Conserving intact forests remains crucial for safeguarding the evolutionary legacy of island bird communities.