Conditional Mutualism in a Membracid‐Ant Association: Temporal, Age‐Specific, and Density‐Dependent Effects

Abstract

Abstract. We examined the impact of a tending ant, Formica altipetens, on the population dynamics of a membracid, Publilia modesta. Controlled ant-exclusion experiments revealed three ways in which the strength and occurrence of this mutualism was conditional. First, we detected yearly variation in the impact of ants on membracids. Ants had a significant positive impact on membracid abundance in 1985 and 1987, but not in 1986. Second, we found age-specific effects of ants on membracids. In 1985 and 1987 our experiments revealed that only membracid nymphs benefit directly from ant tending; we did not detect a direct positive impact of ants on the survival of membracid adults in any year. Third, we documented a density-dependent effect of ants on membracids. In 1985 and 1987, nymphs in large aggregations benefited from ant tending more than nymphs in small aggregations.Observations in 1985-1987 suggest that protection from a predatory salticid spider, Pellenes sp., may be at least one mechanism by which ants benefit membracid nymphs. In 1985 and 1987, when the association was mutualistic, spiders were significantly more abundant on membracid-infested plants without ants than on infested plants with ants, whereas this was not the case in 1986. We hypothesize that the age-specific benefits in this system may result because nymphs are especially susceptible to predation by spiders whereas the more agile and sclerotized adults are not.

Allee dynamics generated by protection mutualisms can drive oscillations in trophic cascades

“…Although relatively little is known about the benefits and dynamics of the participants in many of these interactions (Bronstein and Barbosa 2002), ant-herbivore protection mutualisms are a particularly well-studied category of protection mutualism, so we use a plant-herbivorepredator-ant system to motivate our model. Ant-tended herbivores are insects (e.g., aphids and caterpillars) that excrete or secrete sugar rewards in return for protection from predators (Buckley 1987;Cushman and Whitham 1989;Morales 2000b;Pierce and Easteal 1986). Often the rewards are metabolic byproducts that involve little or no cost to produce.…”

The outcomes of an ant-treehopper association on Solanum lycocarpum St. Hill: increased membracid fecundity and reduced damage by chewing herbivores

“…Oliveira 1999) and in turn provide a range of benefits to the hemipterans, including protection against natural enemies and increased fecundity (Bristow 1983, Cushman & Whitham 1989, Billick & Tonkel 2003.…”

“…This is true also for ant-hemipteran interactions because antderived benefits may vary with factors such as the size and developmental stage of hemipteran aggregations, species and behavior of ant partner, and predator abundance (Cushman & Whitham 1989, Brenton & Addicott 1992, Del-Claro & Oliveira 2000. Ant-Hemiptera interactions can positively affect plant fitness if the benefits of antderived protection from herbivory outweigh the losses incurred by hemipteran feeding (Carroll & Janzen 1973, Janzen 1979.…”

Intra- and interspecific interactions and environmental factors determine spatial–temporal species assemblages of rodents in arid grasslands

“…Between-species interactions relating to competition or mutualism may be important as well in affecting the community structure (Cushman and Whitham 1989;Viljugrein et al 2005;Mutshinda et al 2008). Density dependence has been widely detected in many species (Turchin 1990;Saitoh et al 1997;Lima et al 2006;Wang et al 2009;Yan et al 2012), but its role in maintaining species coexistence of a community has not been investigated in comparison to the role of interspecific interactions.…”