DOI: 10.5061/dryad.6hdr7sqx4
title: Data from: Environmental heterogeneity dynamics drive plant diversity on oceanic islands

description: Aim: The General Dynamic Model (GDM) links island biogeographical
 processes to island geological history. A key premise of the GDM implies
 that environmental factors shaping the ecology and evolution of insular
 biota follow a hump-shaped trend over the island’s life span and drive
 dynamics in carrying capacity, species diversity and endemism. An
 important component of the GDM is environmental heterogeneity (EH), but
 its effects on insular diversity remain poorly understood. Here, we first
 quantified EH, tested whether EH follows the expected hump-shaped trend
 along island ontogeny and evaluated how EH relates to plant diversity.
 Location: 135 oceanic islands of volcanic origin. Taxon: Vascular plants.
 Methods: We calculated 20 alternative EH metrics for focusing on
 topographic and climatic components of EH, and comparing whole-island
 metrics (e.g., range) and moving-window metrics (e.g., roughness). Using
 linear mixed-effects models, we evaluated the trends of EH with island age
 and the EH-plant diversity relationship expected based on the GDM.
 Results: Our analysis revealed some EH components to be collinear, e.g.,
 elevation and temperature heterogeneity, but also underlined that EH
 metrics capture different aspects of EH, e.g., climatic gradients vs.
 climatic complexity. EH generally followed a hump-shaped trend with island
 age with an early peak in island ontogeny. Among the EH components,
 climatic heterogeneity had the strongest effect on plant species richness
 and elevation heterogeneity on endemism. Including EH into previous
 analytical models to test the GDM improved their predictive power. Main
 conclusions: The EH metrics compared here captured various attributes of
 the environment that influence insular plant diversity. In line with the
 GDM, our results strongly support the hump-shaped relationship between EH
 and island age, suggesting that islands become highly heterogeneous early
 in their ontogeny. Finally, the contribution of EH to GDM-based models of
 species richness and endemism suggests that EH is a main driver of the
 diversity of oceanic island biotas.
description: Data analysed and produced in this study 1.
 Number of native and single-island endemic species, age, area and
 archipelago information per island were obtained from the Global Inventory
 of Floras and Traits (GIFT). The GIFT database provides information of
 distributions and floristic status (native, endemic, alien) of plant
 species based on a wide range of regional floristic databases, floras and
 checklists (Weigelt et al., 2020) 2. Information of
 environmental components: 1.1. Elevation was downloaded
 from URL:
 https://cgiarcsi.community/data/srtm-90m-digital-elevation-database-v4-1/.
 Heat load index, was derived from elevation data using the Spatial Analyst
 extension and the Geomorphometry & Gradient Metrics toolbox (Evans
 et al., 2014) in ESRI ArcGIS version 10.4. URL:
 https://github.com/jeffreyevans/GradientMetrics. 1.2
 Precipitation and temperature were downloaded from URL: http://chelsa-climate.org/ 1.3. Heterogeneity rasters were produced using the Spatial Analyst extension and the Geomorphometry & Gradient Metrics toolbox (Evans et al., 2014) in ESRI ArcGIS version 10.4. 3. The code created in R software is also available. With the code EH metrics can be calculated and statistical anylsis can be reproduced.