Rarity is a more reliable indicator of land-use impacts on soil invertebrate communities than other diversity metrics

Abstract

The effects of land use on soil invertebrates – an important ecosystem component – are poorly understood. We investigated land-use impacts on a comprehensive range of soil invertebrates across New Zealand, measured using DNA metabarcoding and six biodiversity metrics. Rarity and phylogenetic rarity – direct measures of the number of species or the portion of a phylogeny unique to a site – showed stronger, more consistent responses across taxa to land use than widely used metrics of species richness, effective species numbers, and phylogenetic diversity. Overall, phylogenetic rarity explained the highest proportion of land use-related variance. Rarity declined from natural forest to planted forest, grassland, and perennial cropland for most soil invertebrate taxa, demonstrating pervasive impacts of agricultural land use on soil invertebrate communities. Commonly used diversity metrics may underestimate the impacts of land use on soil invertebrates, whereas rarity provides clearer and more consistent evidence of these impacts.

Changes in diversity and community assembly of jumping spiders (Araneae: Salticidae) after rainforest conversion to rubber and oil palm plantations

“…The structure of communities and their changes in space and time are often analysed using diversity metrics (Dopheide et al, 2020;Santini et al, 2017). Species richness, a common measure of diversity and an important aspect of community composition, represents a snapshot limited to one point in time.…”

Relationship of taxonomic error to frequency of observation

“…Taxa with the highest RPD values, that is, with greater uncertainty, are documented in smaller numbers of sites ( Table 7 ), corresponding with very rare and rare distribution classes of [ 23 ], and clearly illustrated by UFC1-2 versus UFC4-5 ( Fig 7 ). In general, the more rare a taxon is, the greater is the uncertainty associated with its identity; and the obverse, increasingly common taxa are better known and identified with elevated confidence.…”

“…In this context, it is important to define what is intended by labelling an object (or a taxon) as rare. From a theoretical perspective, rarity has been defined using niche-or phylogenetic-based concepts of abundance, distribution, rarity, or conservation priority-setting [21][22][23][24]. As an operational descriptor, rarity or relative commonness is frequency of encounter or observation.…”

Relationship of taxonomic error to frequency of observation

“…From a theoretical perspective, rarity has been defined using niche-or phylogenetic-based concepts of abundance, distribution, rarity, or conservation priority-setting [20][21][22][23] . As an operational descriptor, rarity or relative commonness is frequency of encounter or observation.…”