A positive association between ants and spiders and potential mechanisms driving the pattern

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Biotic interactions play a central role in determining species distribution and abundance. Some ants act as keystone species affecting the distribution and abundance of other species, including spiders. In coffee plantations Pocobletus sp. spiders are significantly more abundant in coffee plants patrolled by the aggressive arboreal ants Azteca sericeasur. However, it is unknown if other ant species influence this ant-spider association, how these associates are spatially distributed, and which are the potential drivers of this association. Here we examine the influence of ants, Azteca sericeasur and Pheidole synanthropica, and coffee branch density on Pocobletus abundance in a coffee farm in southern Mexico. We also analyze the spatial distribution and abundance of Pocobletus sp., in relation to the spatial distribution of A. sericeasur and P. synanthropica. Finally, we examine prey availability and enemy-free space as potential mechanisms underlying this ant-spider association. Results show that Pocobletus abundance is positively correlated with coffee branch density and A. sericeasur and P. synanthropica presence. Furthermore, the spatial distribution analysis shows that in 20  20 m plots Pocobletus is strongly associated to A. sericeasur, but not to P. synanthropica. Results show that insect abundance in both Pocobletus's webs and sticky traps was significantly higher in the presence of A. sericeasur whereas the abundance of the predators of Pocobletus decreased in A. sericeasur's presence; suggesting positive direct and indirect effects of A. sericeasur on Pocobletus. Overall, this study highlights the strong influence of ants and plant characteristics on the abundance and spatial distribution of spiders as well their indirect effects on other taxa. eng