The importance of competition and facilitation for global tree diversity

Steven

The importance of competition and facilitation for global tree diversity

Article meta

Article Date: 08 April 2026
Article URL: https://www.nature.com/articles/s41586-026-10349-2
Article Image: none provided in source

Summary

This Nature paper analyses how local species interactions — competition and facilitation — contribute to global patterns of tree diversity. Using data from 17 permanent forest plots (largely from the ForestGEO network) the authors computed neighbourhood-level metrics (relative neighbourhood abundance, RNA, and relative neighbourhood richness, RNS) within small circular neighbourhoods (r = 2 m and up to 60 m for some analyses) around focal trees. They classify species as having net facilitative or competitive effects on neighbours and test patterns across latitude, accounting for altitude and other environmental covariates.

Key empirical findings: the proportion of facilitative species declines with increasing latitude (that is, facilitation is stronger near the tropics), results remain after excluding the largest trees, and null-model and spatial-simulation tests suggest these patterns are not a simple sampling artefact. The study provides data and analysis scripts on ForestGEO, GitHub and Code Ocean for reproducibility.

Key Points

  • The study uses 17 globally distributed forest plots and neighbourhood metrics (RNA and RNS) to quantify species-level positive and negative interactions.
  • Proportion of facilitative species decreases with latitude — facilitation is relatively more important in tropical plots than temperate ones.
  • Results hold when excluding the 5%–10% largest trees, and when using a local random labelling null model to test significance.
  • Spatially explicit neutral-model simulations indicate the latitudinal pattern is not explained by simple sampling or neutral dispersal processes.
  • All data and code underpinning analyses are available: plot data via ForestGEO (request), running results and R scripts on GitHub (mdetto/Positive-Interactions) and simulations on Code Ocean.

Context and relevance

This paper speaks directly to debates about the drivers of the latitudinal diversity gradient. It demonstrates that local biotic interactions — both competitive and facilitative — vary with latitude and can influence local richness patterns. That matters for eco-evolutionary theory, for predictive models of biodiversity under climate change, and for conservation/management strategies that rely on understanding local assembly processes.

Why should I read this?

Quick and dirty: if you want to know why tropical forests pack more tree species than temperate ones, this paper shows that positive interactions (facilitation) are chunkier in the tropics and help explain local diversity. It’s not just competition everywhere — facilitation shifts with latitude, and the authors back that up with robust tests and open code/data. Saves you the slog of reading the full methods unless you’re into the stats.

Author take / Tone

Punchy and important — a large multi-institution team provides strong evidence that biotic interactions are unevenly distributed across the globe and are a non-trivial piece of the diversity puzzle. If you work on forest ecology, biodiversity theory or conservation planning, the details are worth digging into.

Source

Source: https://www.nature.com/articles/s41586-026-10349-2

Data & code

Plot data: available on request via ForestGEO (https://www.forestgeo.si.edu/). Analysis scripts and extended-data code: GitHub (https://github.com/mdetto/Positive-Interactions). Simulation code: Code Ocean capsule (https://codeocean.com/capsule/4844196/tree).