Intraspecific Abundance\u2013Occupancy\u2013Patchiness Relations in the Intertidal Benthic Macrofauna of a Cool-Temperate North Sea Mudflat

R S K Barnes

doi:10.1007/s12237-021-00998-z

Abstract

The macroecological variable of patchiness (Lloyd’s Ip index of patchiness, P) has recently been shown to be related inter- and intraspecifically to those of abundance (numbers m−2, A), and occupancy (% occurrence in samples, O) in lower latitude seagrass macrofaunas. For the first time in higher latitudes, intraspecific relationships between three spatial variables were investigated in the intertidal mudflat macrobenthos of the Scolt Head barrier island, southern North Sea (53° N, 01° E). Sampling was conducted between early July and late September 2009–2013 using 710-µm mesh for sample processing. Strong positive interspecific A-O and negative interspecific P-O and P-A relationships were present. Two of the most numerous and widespread assemblage components, however, occurred with effectively constant occupancy (Peringia ulvae, 100%, and Tubificoides benedii, 93%) across the whole 20-ha locality and therefore could not show intraspecific relationships of occupancy with other macroecological metrics. These two apart, only one other dominant species failed to show a significant positive intraspecific A-O relationship; no species showed significant P-A relations of any form; and only two showed the negative P-O ones that have been described elsewhere. The intraspecific A-O patterns appear to contrast with those of an earlier study at another North Sea locality (the Dutch Wadden Sea), although differences are more apparent than real, but the Scolt Head fauna showed fewer intraspecific P-O and P-A relations than those characterising similar circumstances in the two lower-latitude localities previously investigated. Neither developmental mode nor variation in local abundance appears to influence these patterns. A-O-P relations therefore seem widespread but may be subject to latitudinal modification.

Highlights

The interspecific macroecological spatial abundance–occupancy (A-O) relationship is much researched and well-attested across a wide range of habitat types (Verberk et al 2010; Frisk et al 2011; Dallas et al 2019; Miranda and Killgore 2019)
It has been demonstrated in those same southern-hemisphere seagrass meadows that the dispersion pattern of the invertebrate macrofaunal species, as assessed by the Ip patchiness index of Lloyd (1967) (P), is negatively related to both their interspecific abundance and occupancy (Barnes 2021a), so that the three macroecological metrics appear interlinked, at least in a seagrass habitat
The degree of patchiness of the whole assemblage was uniform across all sites (Prob = 0.024), as was that of three of the individual species, Peringia ulvae, Tubificoides benedii, and Pygospio elegans (Prob = 0.02–0.049)

Summary

Introduction

The interspecific (i.e. between-species) macroecological spatial abundance–occupancy (A-O) relationship is much researched and well-attested across a wide range of habitat types (Verberk et al 2010; Frisk et al 2011; Dallas et al 2019; Miranda and Killgore 2019). Values of occupancy associated with the macrofaunal elements of intertidal seagrass beds in the subtropical Moreton Bay, Australia, and in the warm-temperate Knysna estuarine bay, South Africa, can be predicted with great accuracy solely from local abundance data (Barnes 2021a) using the general A-O expression proposed by He and Gaston (2003) It has been demonstrated in those same southern-hemisphere seagrass meadows that the dispersion pattern of the invertebrate macrofaunal species, as assessed by the Ip patchiness index of Lloyd (1967) (P), is negatively related to both their interspecific abundance and occupancy (Barnes 2021a), so that the three macroecological metrics appear interlinked, at least in a seagrass habitat.

Methods

Results

Conclusion