Conclusion
Functional explanations for herbivore coexistence rely largely on our
knowledge of differences in species’ resource niches (Prins & Olff
1998; Arsenault & Owen-Smith 2011; Kartzinel et al. 2015),
whereas population dynamics and diversity are normally linked with
demography and reproductive rates (Sinclair 2003; Owen-Smith 2006). Our
results suggest that these explanations might be mismatched. Instead, it
seems that species’ fitness is sufficiently similar to enable
coexistence over a wide range of niche overlaps, which implies that
fitness equivalence is a more important condition for species’
coexistence than niche partitioning. By contrast, niche partitioning is
closely related to species’ invasion growth rates and, therefore, to
their population dynamics. Thus, MCT provides valuable new insights into
understanding herbivore communities. In particular, MCT demonstrates
that concepts linking herbivore functional traits with fitness, which
traditionally emphasize putative differences among species, should
expand their focus to include more detailed evaluation of processes that
ensure similarities in species’ abilities to convert poor quality
resources (plants) into offspring.