DOI: 10.5061/dryad.0000000bh
title: Fungi and deadwood diversity: A test of the area-heterogeneity trade-off hypothesis

description: Environmental heterogeneity is one of the most fundamental drivers of
 species diversity. For decades, ecologists have suggested that
 heterogeneity-diversity relationships are generally positive. But today, a
 greater variety of heterogeneity-diversity relationships is discussed. In
 this study, we contrasted two hypotheses for wood-inhabiting fungi: The
 classical heterogeneity-diversity hypothesis, that predicts positive
 relationships due to an increase in niche dimensionality with increasing
 heterogeneity. And the more recently stated area-heterogeneity trade-off
 hypothesis, that predicts a unimodal pattern due to an inherent trade-off
 between the number of occupied niches and the effective area per species.
 It allows positive and negative relationships only as special cases. We
 sampled 3,715 deadwood objects on 135 plots along a forest structure
 gradient in the Black Forest, Germany, and recorded 284 wood-inhabiting
 fungal species. To assess heterogeneity of deadwood structures, we
 calculated two multidimensional structural diversity indices: Structural
 richness was used as a measure of available niche space, and structural
 divergence as a measure of multivariate variance within that niche space.
 Those indices were then related to species richness estimates for rare,
 common, and dominant species, using the framework of Hill numbers. We
 found a linear, positive effect of structural richness and a unimodal
 effect for structural divergence on estimated species diversity.
 Structural richness, but not structural divergence was strongly correlated
 with the number of sampled deadwood objects. No clear differences between
 the responses of rare, common, and dominant species to the two
 heterogeneity gradients were found. We also estimated the mean abundance
 as proxy for mean population size, which decreased significantly with
 structural richness, but was non-significantly related to structural
 divergence. Synthesis: In general, the results of this study suggest a
 unimodal heterogeneity-diversity relationship for deadwood-inhabiting
 fungi, and are thereby in line with the area-heterogeneity trade-off
 hypothesis. Thus, the negative effect of heterogeneity should lead to
 lower species richness and higher risk of stochastic extinctions at high
 levels of heterogeneity. However, as deadwood amount and deadwood
 diversity are often strongly correlated, we argue that the positive effect
 of resource availability on species richness may mask the negative effect
 of structural heterogeneity in some cases.
description: # Fungi and deadwood diversity: A test of the area-heterogeneity trade-off
 hypothesis
 [https://doi.org/10.5061/dryad.0000000bh](https://doi.org/10.5061/dryad.0000000bh) The dataset contains species diversity estimates, environmental variables, and a community matrix for 135 study plots. Species records of wood-inhabiting fungi are based on field surveys conducted in south-west Germany in 2020.  ## Description of the data and file structure The plot-level dataset contains one row per study plot with species diversity estimates for wood-inhabiting fungi and environmental variables. A community matrix is also included. The abbreviations of the species diversity estimates and environmental variables are listed below. Further information on the study design, sampling method, and the calculation of the environmental variables 'structural richness' and 'structural divergence' is given in the associated manuscript. ##### Column names Plot_ID: identifier for study plot q0: species diversity estimate for Hill number of order q = 0 q1: species diversity estimate for Hill number of order q = 1 q2: species diversity estimate for Hill number of order q = 2 SR: species richness (raw species density) Rao: structural divergence, calculated as multivariate variance (Rao's entropy) log_stRi: structural richness, calculated as multivariate range nDW: number of sampled deadwood objects FT: forest type category (coniferous forest, broadleaved forest, mixed forest) ntyp_trgen: number of types - tree genera ntyp_trfam: number of types - tree families ntyp_trclass: number of types - tree classes ntyp_dw_pos: number of types - deadwood positions range_diam: range - deadwood diameter range_bryo: range - deadwood bryophyte cover range_bark: range - deadwood bark cover range_cont: range - deadwood soil contact range_decst: range - deadwood decay stages var_diam: variance - deadwood diameter var_bryo: variance - deadwood bryophyte cover var_bark: variance - deadwood bark cover var_cont: variance - deadwood soil contact var_decst: variance - deadwood decay stages Alutaceodontia_alutacea - Xylodon_spathulatus: community matrix, numbers indicate the number of species records