Many More Consumers Not Always Induce Stronger Competition: Weaker Interspecific Competition Despite Higher Species Richness in Secondary Feeding Guild, as Compared to Primary

Abstract

The species functional structuration (specifically in terms of species richness and average intensity of interspecific competition) is widely varying among species communities and this point is now very well documented in literature. But, what about the species functional structuration within the different feeding guilds that coexist in a same local community – in particular the primary and the secondary feeding guilds? Are there significant differences – or not – between them in this respect? This rather fundamental issue does not seem having been addressed yet, at least using appropriate investigative tools. However, a series of recently published case studies, precisely implementing such an adequate investigative approach, now deserves full consideration in this regard and makes the subject of the present review. Substantially, it results from this preliminary survey of the question that marked differences in the patterns of species functional structuration clearly singularize the secondary from the primary feeding guilds, within a same local community. More precisely, a consistent trend seems to arise, highlighting both: (i) a markedly greater species richness and, yet somewhat unexpectedly, (ii) a significantly reduced intensity in interspecific competition within secondary feeding guild as compared to primary. The point is discussed and interpreted as being the consequence of the fact that secondary feeders (typically carnivores) have obviously evolve quite more diversified feeding behaviors than did the primary feeders (typically herbivores).