DOI: 10.5061/dryad.4f4qrfjrq
title: Quantifying species distribution within the functional space

description: Multidimensional representations of functional diversity help visualize
 species and organism distribution in functional space, providing insights
 into the mechanisms regulating community assembly and ecosystem
 functioning. Typically, the species distributions in functional space are
 represented by richness, divergence (or dispersion) and evenness (or
 regularity). While these dimensions quantify the overall structure of
 species distribution, they overlook how exactly species are scattered
 within the functional space, particularly the fine-scale spatial patterns
 that may reveal additional ecological or evolutionary dynamics. We
 introduce a novel framework to quantify species’ functional arrangement
 within the functional space, capturing patterns across broad and fine
 scales. We detail the construction of a functional space and propose
 statistics to assess species functional arrangement - the cumulative
 proportion of pairwise neighbours (PNcp) and the cumulative proportion of
 nearest neighbours (NNcp). We also outline guidelines for evaluating
 departures from randomness using null models, including random
 displacement and random selection from species pool. To demonstrate this
 framework, we tested it in simulated scenarios and analysed the functional
 arrangement patterns of vascular plant species on Surtsey Island. In the
 simulated scenarios, the framework correctly identified simulated patterns
 at multiple scales. As for the colonization of Surtsey Island, our
 findings showed a gradual reorganization of species within the functional
 space. Initially random, the distribution shifted towards clustering,
 reflecting increasing habitat complexity and the formation of ecological
 relationships among plant species. This pattern aligns with succession
 theory, where early arrivals create conditions that favour later
 colonizers, leading to a more interconnected and structured ecosystem. Our
 framework allows to advance from global (richness, dispersion and
 evenness) to fine-scale (arrangement) functional distribution patterns,
 adopting rigorous, quantitative methods that can test specific ecological
 hypotheses and uncover deeper insights into community assembly and the
 functioning of ecosystems. By assessing functional arrangement, it enables
 researchers to address a broader range of functional diversity questions
 than previously possible. The methods presented here offer a powerful
 approach to uncover and interpret complex patterns in functional diversity
 occurring at multiple scales.
description: ### Description of Files * **SimStudy_MEE_FINAL.R** – R script for the
 simulation study described in the manuscript. *
 **SurtseyPlantsAnalysis_MEE_FINAL.R** – R script for the analysis of the
 Surtsey plant data. * **SI_diff_sigma_FINAL.R** – R script for the
 sensitivity analysis of different sigma (kernel bandwidth) values. ###
 Data Availability No new data were generated for this study. * **Inventory
 data** were obtained from *Magnússon et al.* (2022). * **Trait data** were
 obtained from *Díaz et al.* (2022), including the following traits: *
 Plant height (PH) * Diaspore mass (DM) * Specific stem density (SSD) *
 Leaf dry mass per unit leaf area (LMA) * Leaf nitrogen content on a mass
 basis (LNM) * Leaf area (LA) ### Data Sources Díaz, S., Kattge, J.,
 Cornelissen, J. H. C., Wright, I. J., Lavorel, S., Dray, S., Reu, B.,
 Kleyer, M., Wirth, C., Prentice, I. C., Garnier, E., Bönisch, G., Westoby,
 M., Poorter, H., Reich, P. B., Moles, A. T., Dickie, J., Zanne, A.E.,
 Chave, J., …, Zotz, G. (2022). The global spectrum of plant form and
 function: enhanced species-level trait database. Scientific Data, 9, 755.
 [https://doi.org/10.1038/s41597-022-01774-9](https://doi.org/10.1038/s41597-022-01774-9) Magnússon, S. H., Wasowicz, P., & Magnússon, B. (2022). Vascular plant colonisation, distribution and vegetation development on Surtsey during 1965–2015. Surtsey research, 15, 9-29. [https://doi.org/10.33112/surtsey.15.2](https://doi.org/10.33112/surtsey.15.2)