The size‐grain hypothesis: a phylogenetic and field test

Abstract

1. The size-grain hypothesis predicts that environmental rugosity results in positive allometric scaling of leg length on body length because of changes in locomotion costs.2. The scaling of leg length and body length in ants was re-examined using phylogenetic independent contrast methods, and the allometric relationship found by Kaspari and Weiser (Functional Ecology, 13, 530-538, 1999) was supported.3. The size-grain hypothesis was tested further by comparing the body sizes of ants from areas of contrasting habitat complexity in two different savanna habitats. No support for the size-grain hypothesis was found. Small body size classes were no more speciose in the rugose than in the more planar environment, and small ants were more abundant in the planar environment.

Assembling an ant community: species functional traits reflect environmental filtering

“…Standard linear measurements were taken using an ocular micrometer on a dissecting microscope to determine species means for head width, head length, and total hind leg length (hind tibia length + hind femur length) (Kaspari and Weiser 1999;Parr et al 2003). Relative leg length was measured as the ratio RL = log 10 (total hind leg length + 1) £ [log 10 (head length + 1)]…”

“…These factors may be linked to ant traits in the following ways. First, the size-grain hypothesis posits surface complexity drives an allometric relationship between ant size and leg length, with larger ants having proportionally longer legs than smaller ants (Kaspari and Weiser 1999;Parr et al 2003). This relationship may be a consequence of how ants move through their environment: smaller, shorterlegged ants more successfully forage through the leaf-litter while larger ants forage across it, as longer legs can enable faster or more eYcient movement (Farji-Brener et al 2004;Pearce-Duvet et al 2011a).…”

“…This relationship may be a consequence of how ants move through their environment: smaller, shorterlegged ants more successfully forage through the leaf-litter while larger ants forage across it, as longer legs can enable faster or more eYcient movement (Farji-Brener et al 2004;Pearce-Duvet et al 2011a). As a result, ant assemblages in comparatively low surface complexity environments are expected to contain species of larger sizes and greater relative leg lengths (Parr et al 2003;Sarty et al 2006). A study comparing ant body sizes across savanna habitats of contrasting surface complexity in Africa found minimal support for this prediction (Parr et al 2003), although further evidence is needed to assess the generality of this pattern.…”

“…As a result, ant assemblages in comparatively low surface complexity environments are expected to contain species of larger sizes and greater relative leg lengths (Parr et al 2003;Sarty et al 2006). A study comparing ant body sizes across savanna habitats of contrasting surface complexity in Africa found minimal support for this prediction (Parr et al 2003), although further evidence is needed to assess the generality of this pattern.…”

The size–grain hypothesis: do macroarthropods see a fractal world?

“…Subsequently, this allometry has been confirmed in a variety of native ant assemblages (Kaspari & Weiser, 1999;Espadaler & Gomez, 2000;Parr et al, 2003;Farji-Brener, 2004;Farji-Brener et al, 2004) but not an island assemblage recently assembled from invasives (Sarty et al, 2006). But is this allometry robust?…”