DOI: 10.5061/dryad.wpzgmsbv7
title: Habitat quality drives the species-area relationship of plants and soil microbes in an ocean archipelago

description: While the positive species-area relationship on islands is frequently
 observed, the mechanisms underlying this pattern remain poorly studied. By
 analyzing insular community diversity across spatial scales and the soil
 properties within the islands, we were able to explore potential
 mechanisms leading to the island species-area relationship of plants, as
 well as associated soil bacteria and fungi, from a tropical archipelago.
 We found that both plant and soil microbial communities showed similar
 positive species-area relationships across scales and the greater
 taxonomic diversity on larger islands was mainly driven by the higher
 richness within samples. These patterns arose primarily due to shifting
 habitat quality with island area, rather than spatial processes generally
 attributed to species-area relationships. Specifically, for plants,
 changes in soil total phosphorus content with island area were most
 explanatory, while changes in soil pH appeared to play the most important
 role in shaping soil bacteria and fungi patterns. By contrast, we found
 little evidence for the role of spatial processes (i.e., dispersal
 limitation or soil heterogeneity) within the island. Overall, this study
 highlights the importance of dissecting potential mechanisms underlying
 multi-trophic community dynamics to explain patterns of biodiversity and
 its variation on islands.
description: ReadMe for 'Habitat quality drives the species-area relationship of
 plants and microbes in an ocean archipelago'. Our dataset was
 collected from the Paracel archipelago (i.e., Xisha islands, 15°46′ N to
 17°08′ N and 111°11′ E to 112°54′ E) in the South China Sea. The Paracel
 archipelago comprises many small oceanic islands primarily made from coral
 and sand (Ye et al., 1985; Gong et al., 1996). The vegetation on these
 islands consists mainly of shrubs and herbs, with dominant plant species
 including Scaevola taccada, Guettarda speciosa, Tournefortia argentea and
 Morinda citrifolia. Although there are ~30 islands in the Paracel
 archipelago, many of them are too small or lack vegetation to meet the
 requirements for field surveys. Thus, in April 2023, ten representative
 islands were selected with an area ranging from 2 to 40ha that were
 minimally disturbed by human activities. On each island, woody plants,
 together with soil bacteria and fungi, were sampled simultaneously. This
 readme file describes the data files accompanying the above manuscript. If
 you have any questions, please contact
 [ykcheng@hainanu.edu.cn](mailto:ykcheng@hainanu.edu.cn) The following
 files are included: **1) SEM.csv**（all variables were log-transformed）
 This data file contains all variables to disentangle the causal pathways
 through which island spatial and environmental factors influence alpha,
 beta, and gamma diversity of plant, soil bacteria and fungi. area: the
 size of each island (ha) soil: average soil heterogeneity among samples
 within each island spatial: average spatial distance among samples within
 each island bg: bacteria gamma diversity of each island pg: plant gamma
 diversity of each island fg: fungi gamma diversity of each island area:
 island area fa:average fungi alpha diversity within each island pa:
 average plant alpha diversity within each island ba: average bacteria
 alpga diversity within each island ph: average soil pH within each island
 tsc: average soil salinity within each island tn: average soil total
 nitrogen content within each island tp: average soil total phosphorus
 content within each island soc: average soil organic carbon within each
 island tk: average soil total potassium within each island bb: bacteria
 beta diversity (the average bray-curtis dissimilarity of bacteria
 community among samples within each island) fb: fungi beta diversity (the
 average bray-curtis dissimilarity of fungi community among samples within
 each island) pb: plant beta diversity (the average bray-curtis
 dissimilarity of plant community among samples within each island) **2)
 alpha-plant.csv** area: the size of each island (ha) plant_richness: the
 sample-level taxonomic richness of plant within each island site: sample
 site number **3) alpha-bf.csv** area: the size of each island (ha)
 bac_richness: the sample-level taxonomic richness of bacteria within each
 island fungi_richness: the sample-level taxonomic richness of fungi within
 each island Plot: sample plot number **4) beta-plant.csv** area: the size
 of each island (ha) plant_bray: the bray-curtis dissimilarity of plant
 among samples within each island plant_jaccard: the jaccard dissimilarity
 of plant among samples within each island Site: sample site name **5)
 beta-bf.csv** area: the size of each island (ha) bac_bray: the bray-curtis
 dissimilarity of bacteria among samples within each island bac_jaccard:
 the jaccard dissimilarity of bacteria among samples within each island
 fungi_bray: the bray-curtis dissimilarity of fungi among samples within
 each island fungi_jaccard: the jaccard dissimilarity of fungi among
 samples within each island Site: sample site name These data files were
 used to test the effect of island area on plant and soil microbe
 diversities. (2-5)