Predators affect plant fitness when they forage on them and reduce the action of herbivores. Our study evaluates the complementary effects of spiders and ants that visit the extrafloral nectaries of Eriotheca gracilipes (Malvaceae) on the production of fruits and viable seeds of these savanna trees. Four experimental groups were established: control group – with free access of spiders and ants; exclusion group – spiders and ants excluded; ant group – absence of spiders; and spider group – absence of ants. The presence of ants reduced the spider richness; however, the presence of spiders did not affect the ant richness. A significantly higher number of fruits per buds were found in the presence of spiders alone or spiders and ants together (control group) compared with the absence of both predators (exclusion group). The number of seeds per fruits and seed viability were higher in the control group. This is the first study showing that spiders and ants may exert a positive and complementary effect on the reproductive value of an extrafloral nectaried plant. Mostly the impact of ants and/or spiders on herbivores is considered, whereas our study reinforces the importance of evaluating the effect of multiple predators simultaneously, exploring how the interactions among predators with distinct skills may affect the herbivores and the plants on which they forage.
The central tendency in ecological studies to explain variations in the outcomes of biotic interactions is to suppose that the majority of meaningful functional diversity occurs at the species level. However, individuals are rarely identical and behavioral ecology shows that consistent individual differences alter the roles that individuals play within populations and possibly communities, but the intraspecific variation is commonly ignored in studies of species interactions. Here, throughout examples of field work studies, we discuss that the knowledge of individual aspects (including genetic variation) and natural history are basic tools and fundamental to a real and whole comprehension of species interaction networks in qualitative and quantitative terms.
Mechanisms promoting stable coexistence allow multiple species to persist in the same trophic level of a given network of species interactions. One of the most common stabilizing mechanisms of coexistence is niche differentiation, such as temporal and spatial patchiness. To understand the limits of coexistence between species we have to understand the limits of competitive interactions which translate in species exclusion or patterns of non‐co‐occurrence.
We evaluated spatiotemporal niche‐based mechanisms that could promote stable coexistence between ants and spiders which forage on extrafloral nectary (EFN)‐bearing plants. We observed co‐occurrence and overlapping patterns between ants and spiders in a temporal and spatial scale in nine different EFN‐bearing plant species in a Neotropical savanna, using both community and species‐level approach.
Ants and spiders showed asynchrony of their abundances over the year with low temporal overlapping patterns between them (temporal niche specialization). Greater abundance of ants occurred between September and March, whereas greater abundance of spiders occurred between March and August, exactly at the time when the abundance of ants decreases on plants. However, there might also be some levels of temporal overlapping, but then individual ants and spiders occupy different branches (spatial segregation). Finally, we also observed a spatial negative effect of the abundance of ants on the presence of spiders.
Our results suggest that spatiotemporal partitioning between ants and spiders may be one of the potential mechanisms behind a stable coexistence between these two groups of organisms that forage on EFN‐bearing plants in the Brazilian savanna.
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