Abstract
Despite the importance and increasing knowledge of ecological networks, sampling effort and intrapopulation variation has been widely overlooked. Using continuous daily sampling of ants visiting three plant species in the Brazilian Neotropical savanna, we evaluated for the first time the topological structure over 24 h and species-area relationships (based on the number of extrafloral nectaries available) in individual-based ant-plant networks. We observed that diurnal and nocturnal ant-plant networks exhibited the same pattern of interactions: a nested and non-modular pattern and an average level of network specialization. Despite the high similarity in the ants’ composition between the two collection periods, ant species found in the central core of highly interacting species totally changed between diurnal and nocturnal sampling for all plant species. In other words, this “night-turnover” suggests that the ecological dynamics of these ant-plant interactions can be temporally partitioned (day and night) at a small spatial scale. Thus, it is possible that in some cases processes shaping mutualistic networks formed by protective ants and plants may be underestimated by diurnal sampling alone. Moreover, we did not observe any effect of the number of extrafloral nectaries on ant richness and their foraging on such plants in any of the studied ant-plant networks. We hypothesize that competitively superior ants could monopolize individual plants and allow the coexistence of only a few other ant species, however, other alternative hypotheses are also discussed. Thus, sampling period and species-area relationship produces basic information that increases our confidence in how individual-based ant-plant networks are structured, and the need to consider nocturnal records in ant-plant network sampling design so as to decrease inappropriate inferences.
Highlights
Ants and plants can interact in different ways, from facultative to highly specialized relationships [1]
We observed an average level of network specialization in both diurnal and nocturnal networks
Using an intrapopulation approach and three plant species, we evaluated the structure of individual-based ant-plant networks in both diurnal and nocturnal sampling in the Brazilian Neotropical savanna
Summary
Ants and plants can interact in different ways, from facultative to highly specialized relationships [1]. Focused on the structure of ant-plant ecological networks, some studies have found some non-random patterns of interactions around the world as, for example, the nested pattern [4,7,8]. This pattern indicates that within an ant-plant network there is a core of generalist species (those with the most interactions), which interact among themselves, and specialists species (those with fewer interactions) interacting with the generalist species in cohesive subgroups [9]. As a single EFN-bearing plant can be associated to several ant species in a predictable way, we can use a network approach to evaluate the structure of such individual-based ant-plant networks
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