Emergent Impacts of Ant and Spider Interactions: Herbivory Reduction in a Tropical Savanna Tree

Abstract

Multiple predators often have effects on their common prey populations that cannot be predicted by summing the effects of each predator at a time. When predators forage on the same vegetation substrate, intraguild interactions might cause emergent outcomes for the plants on which the predators co-occur. We experimentally evaluated the effects of spiders and ants on herbivory and reproduction in the extrafloral nectary-bearing tree Qualea multiflora (Vochysiaceae). Plants were divided in four experimental groups, depending on the presence or absence of ants and spiders. We compared the effects of each treatment on richness and abundance of chewing and sucking herbivores and on herbivory (leaf area loss). We also evaluated the impact of predators on the production of buds, fruits and seeds, and weight of the fruits. The presence of ants reduced the abundance and richness of spiders, but spiders did not affect the abundance and richness of ants. Only the removal of ants resulted in a significant increase in the abundance of herbivores and herbivore richness. Herbivory, however, was also affected by spiders. In addition, we found a significant interaction effect of ants and spiders on herbivory, indicating an emergent multiple predator effect. Neither ants nor spiders had an impact on the number of buds produced, number of fruits per bud, and seeds per fruits or fruit weight. This study highlights the importance of evaluating the effect of the predator fauna as a whole and not only one specific group on herbivory.Abstract in Portuguese is available in the online version of this article.

First observation of alternative food usage (extrafloral nectar) by the assassin bug Atopozelus opsimus (Hemiptera, Reduviidae)

“…Recent evidences have shown that such food resource may be crucial for insect development (Byk & Del-Claro 2011) and is part of the diet of many predatory arthropods like ants (Nascimento & Del-Claro 2010) and spiders (Nahas et al 2012). Since nymphs of A. opsimus may feed more frequently on nectar than on prey, plant derived substances may even be enough for nymph development like Stoner et al (1975) suggested.…”

“…A large group of animals are attracted to EFNs (Koptur 1992), such as spiders (Ruhren & Handel 1999;Nahas et al 2012) and ants (Oliveira & Brandão 1991;Nascimento & Del-Claro 2010) which provide protection to the plant against herbivores. In return, the animals get the nectar which is an important part of nutrition and can enhance growth and reproduction (Byk & Del-Claro 2011).…”

Evidences that human disturbance simplify the ant fauna associated a Stachytarpheta glabra Cham. (Verbenaceae) compromising the benefits of ant-plant mutualism

“…Species vouchers were deposited in both collections. The species were separated into feeding guilds according to the literature of the taxon (Gibbs et al, 2010;Marinoni et al, 2001;Nahas et al, 2012).…”

The Ecology of Extrafloral Nectar in Senna mexicana var. chapmanii

“…Indeed, in a few cases ants have even been seen to affect plant defense negatively (Frederickson and Gordon 2007;Mooney 2007;). Conversely, overly aggressive ants may deter beneficial insects such as predators (Torres-Hernandez et al 2000;Nahas et al 2012), parasitoids (Styrsky and Eubanks 2007;), and pollinators (Ness 2006;Hernández-Cumplido et al 2010;Assunção et al 2014). Several studies have shown that pollinators recognize the dangers posed by aggressive ants (Hernández-Cumplido et al 2010, Assunção et al 2014.…”

“…Conversely, plants that host ants may incur certain ecological costs. Aggressive ants have been known to deter beneficial insects such a pollinators (Ness 2006;Hernández-Cumplido et al 2010;Assunção et al 2014), predators (Torres-Hernandez et al 2000Nahas et al 2012;, and parasitoids (Styrsky and Eubanks 2007;). …”