Differential response of ants to nutrient addition in a tropical Brown Food Web

Abstract

a b s t r a c tIn tropical ecosystems, access to nitrogen (N) and phosphorus (P) limits the decomposition rate of leaflitter. Leaf-litter ants are abundant in this microhabitat and present a wide variety of diets. Our aim was to study the response of various ant trophic groups to an increased nutrient availability which boosts the decomposition of their habitat and selectively affects the abundance of their prey.A 6-month nutrient addition experiment (CN, CNP) was performed in a tropical montane forest of the Ecuadorian Andes. The density of ants, of other predators (e.g. arachnids, beetles) and of their potential prey (mesofauna, ranging from 0.1 to 2 mm) was measured in treatments and control plots.The litter volume in fertilized plots decreased significantly. Collembola and total mesofauna density were enhanced by the CNP addition. Ants responded differentially according to their trophic group: despite increased prey availability, predatory species in general and collembolan hunters in particular were negatively affected by both treatments. Other ant trophic group densities did not change. By contrast, the density of Dermaptera increased with the treatments. A complementary isotopic approach allowed us to trace carbon fluxes through the food web.Our results suggest that the nutrient input enhanced the litter decomposition rate, leading to reduction of habitat size. They also suggest that predatory ants in tropical leaf-litter food webs are limited by habitat size rather than by prey availability, and that these ants are more affected by habitat loss than their prey, other ant trophic groups and other macrofauna taxa.

Short-term sodium inputs attract microbi-detritivores and their predators

“…Here we tested Na's effects on food web structure and invertebrate response and controlled for differences in habitat space between treatments, but demonstrated that the addition of Na increases both leaf litter and experimental filter paper decomposition and documented a similar response in termite recruitment to NaCl treated cellulose. The inverse relationship between habitat space and decomposition rates in BFWsdthe "more food-less habitat effect" (Shik and Kaspari, 2010;Jacquemin et al, 2012)dsuggests a dynamic mix of limiting factors for invertebrates as litter decomposes. Our results and those of demonstrate that even ephemeral patchy Na subsidies can have rapid and large effects on both BFW structure and function in Na-poor environments.…”

Leaf litter arthropod responses to tropical forest restoration

“…Predators, namely arachnids (Araneae) and predatory Coleoptera, drove patterns of high arthropod abundance in the island treatments and reference forests. These patterns likely reflect more variable litter, vegetation, and food web structure (e.g., Jacquemin et al 2012). Reference forests hosted significantly higher abundances of mycophagous arthropods, presumably due to the greater presence of fungi and belowground fungal mutualisms that are linked to aboveground insect diversity (e.g., Bennett 2010).…”

Resource use and food preferences in understory ant communities along a complete elevational gradient in Papua New Guinea

“…, Jacquemin et al . ), and therefore, effects of elevation should translate into ecosystem‐level responses (Sundqvist et al . ).…”

“…This has been mainly investigated in plant traits and soil processes, highlighting most of the time reductions of decomposition rates with elevation, which induce changes in nutrient concentrations and ratios and, in turn, can impair plant growth and affect species traits (Fisher et al 2013, Sundqvist et al 2013, He et al 2016. Nutrient limitations not only affect plant growth but also complete food webs (Kaspari et al 2008, Jacquemin et al 2012, and therefore, effects of elevation should translate into ecosystem-level responses (Sundqvist et al 2013).…”