Fungi and deadwood diversity: A test of the area-heterogeneity trade-off hypothesis
Data files
Jun 03, 2024 version files 99.53 KB
Abstract
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.
README: Fungi and deadwood diversity: A test of the area-heterogeneity trade-off hypothesis
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