Abstract
Abstract Plants regulate soils and microclimate, provide substrate for heterotrophic taxa, are easy to observe and identify and have a stable taxonomy, which strongly justifies their use as indicators in monitoring and conservation. However, there is no consensus as to whether plants are strong predictors of total multi‐taxon species richness. In this study, we investigate if general terrestrial species richness can be predicted by vascular plant richness and bioindication. To answer this question, we collected an extensive dataset on species richness of vascular plants, bryophytes, macrofungi, lichens, plant‐galling arthropods, gastropods, spiders, carabid beetles, hoverflies, and genetic richness (operational taxonomic units = OTUs) from environmental DNA metabarcoding. We also constructed a Conservation Index based on threatened red list species. Besides using richness of vascular plants for prediction of other taxonomic groups, we also used plant‐derived calibration of the abiotic environment (moisture, soil fertility and light conditions) as well as the degree of anthropogenic impact. Bivariate relationships between plant species richness and other species groups showed no consistent pattern. After taking environmental calibration by bioindication into account, we found a consistent, and for most groups significant, positive effect of plant richness. Plant species richness was also important for richness of fungal OTUs, Malaise OTUs and for the Conservation Index. Our multiple regression analyses revealed (a) a consistently positive effect of plant richness on other taxa, (b) prediction of 12%–55% of variation in other taxa and 48% of variation in the total species richness when bioindication and plant richness were used as predictors. Our results justify that vascular plants are strong indicators of total biodiversity across environmental gradients and broad taxonomic realms and therefore a natural first choice for biodiversity monitoring and conservation planning.
Highlights
The majority of species worldwide are still undescribed and nowhere on Earth are all the locally resident species known
After bioinformatic processing the soil fungal Operational Taxonomic Units (OTUs) dataset resulted in an OTU richness per site ranging from 66 to 476
The soil eukaryote OTU data had a richness per site ranging from 206 to
Summary
The majority of species worldwide are still undescribed and nowhere on Earth are all the locally resident species known. Even for the vast majority of known species, their distribution range and population sizes remain unknown. Given the global biodiversity crisis, the need for establishing causes for spatial and temporal variation in biodiversity is acute (Hill et al 2016; Ceballos et al 2017). Brunbjerg et al (2017b) proposed ecospace as a unifying framework for assessing and managing variation in biodiversity within regional species pools. Ecospace represents the variation in local environment separated into abiotic position (in environmental hyperspace), biotic expansion (diversification of organic matter) and spatio-temporal continuity. We test whether plant community composition may be used to predict the overall biodiversity through bioindication of abiotic position and biotic expansion in ecospace
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