Isometric scaling of faunal patchiness: Seagrass macrobenthic abundance across small spatial scales

Abstract

Following earlier studies across 2115 → 33 m² scales (Barnes and Laurie, 2018), patchiness of macrobenthic abundance in intertidal Queensland seagrass was assessed by dispersion indices, spatial autocorrelation and hotspot analysis across a hierarchically-nested series of smaller scales (5.75 → 0.09 m²). Overall patterns of distribution and abundance over larger extents and with greater lag were mirrored across these smaller ones. Assemblage abundance per station varied by a factor of >10, but all three approaches showed effective constancy of total assemblage patchiness across all sub-2115 m² scales (across-scales-mean Lloyd's I_P of 1.06 and global Moran's I of 0.13). Equivalent constancy was also shown by most numerically-dominant species (scaling exponent β = 0.93-1.15). Decreasing patchiness of some species with decreasing scale, however, resulted in two no longer being patchily dispersed across small scales. Significant hotspots of abundance occurred at a constant proportion of stations across scales, against a background of randomly scattered peak-abundance points.

Keywords: Benthos; Hotspot analysis; Isometric scaling; Moreton bay; Patchiness; Scale-invariance; Seagrass; Spatial autocorrelation.