The mixed effects of experimental ant removal on seedling distribution, belowground invertebrates, and soil nutrients

Abstract

Abstract. Ants are ubiquitous members of most forest communities, where they disperse seeds, prey on other species, and influence the flow of nutrients. Their effects are often described as substantial, but few studies to date have simultaneously examined how the presence of ants affects both above and belowground processes. In this study, we experimentally reduced ant abundance in a suite of deciduous forest plots in northern Georgia, USA to assess the effects of ants on the spatial distribution of a common understory plant species, Hexastlylis arifolia, the structure of soil mesofaunal communities, and soil nitrogen dynamics. Over the course of several years, the removal of ants led to significant spatial aggregation of H. arifolia seedlings near the parent plant, most likely due to the absence of the keystone seed dispersal species, Aphaenogaster rudis. Seedling emergence was higher in ant removal plots, but seedling aggregation did not affect first or second year seedling mortality. Ammonium concentrations were 103 higher in ant removal plots relative to control plots where ants were present in the first year of the study, but this increase disappeared in the second and third years of the study. The effects of ant removal on the soil mesofauna were mixed: removal of ants apparently did not affect the abundance of Collembola, but the abundance of oribatid mites was significantly higher in ant removal plots by year two of the study. Taken together, these results provide some of the first experimental evidence of the diverse direct and indirect effects of ants on both above and belowground processes in forest ecosystems and demonstrate the potential consequences of losing an important seed dispersing ant species for the plants they disperse.

Forest invader replaces predation but not dispersal services by a keystone species

“…We focused on plant aggregation because the end result of failed seed dispersal by ants is increased seedling clumping around parents. Results from previous studies have linked failed dispersal with unsuitable abiotic habitat for A. rudis (Giladi 2004;Warren II and Bradford 2013;Warren II et al 2010;Zelikova et al 2011). We did not find microclimate associated with plant aggregation, suggesting that ''unsuitable habitat'' in this instance was a biotic consequence of B. chinensis presence.…”

“…Previous work in this study system, primarily focused on A. arifolium, showed that failed ant dispersal results in aggregation as seedlings cluster below parents. The clustering occurred in the absence of A. rudis due to spatial (saturated soil, Giladi 2004;Warren II et al 2010), temporal (phenological asynchrony, Warren II and Bradford 2013) and experimental (Zelikova et al 2011) ant exclusion. Moreover, Rodriguez-Cabal et al (2012 showed that decreased seed retrieval at bait stations corresponded with reduced A. arifolium abundance.…”

Coping with the cold: minimum temperatures and thermal tolerances dominate the ecology of mountain ants

“…Diamond et al, ; Kaspari et al, ). Ants are abundant and ubiquitous on nearly all continents (Fisher, ), display a fascinating diversity of life‐history strategies (Hölldobler & Wilson, ) and are believed to be functionally critical organisms in a range of environments (Evans et al, ; Zelikova et al, ; McGlynn & Poirson, ). Moreover, ants are commonly cited to be a thermophilic group (heat‐loving; Hölldobler & Wilson, ; Kaspari et al, ).…”

Taxonomic and functional ecology of montane ants

“…Ants (Hymenoptera: Formicidae) in mountain environments are used as a model system. Ants are charismatic, globally abundant (Hölldobler and Wilson 1990) and functionally important (Evans et al 2011, Zelikova et al 2011. They also have a strong foundation of taxonomic and methodological literature (Alonso and Agosti 2000).…”