Above- and below-ground effects of an ecosystem engineer ant in Mediterranean dry grasslands

Abstract

Within a local assemblage, ecosystem engineers can have major impacts on population dynamics, community composition and ecosystem functions by transforming or creating new habitats. They act as an ecological filter altering community composition through a set of environmental variables. The impact of ants on their environment has been widely studied, but their multi-component effects (both trophic and non-trophic) have been rarely addressed. We investigated the roles of Messor barbarus , one of the commonest harvester ant species in south-western European Mediterranean grasslands. We analysed soil physico-chemical parameters, above-ground vegetation (e.g. species richness, plant community, micro-local heterogeneity, plant biomass) and above- and below-ground fauna (macrofauna, Collembola, Acari and nematodes). A clear and strong local impact of M. barbarus on soil, vegetation and fauna compartments emerges. The environmental filter is altered by modifications to soil physico-chemical properties, and the biotic filter by changes to plant communities and altered above- and below-ground fauna abundance, occurrence and community structure. The engineering activity of M. barbarus affects not only these separate ecosystem components but also the trophic and non-trophic relationships between them. By altering ecological filters at a local scale, M. barbarus creates habitat heterogeneity that may in turn increase ecological niches in these highly diverse ecosystems.

Impact of three co-occurring physical ecosystem engineers on soil Collembola communities

“…Therefore, these often long-lasting environmental modulations can affect community dynamics of non-engineering species, as these changes may favour some species over others (Jones et al 1997). In addition to structural effects, engineering also affects ecosystem processes, such as litter degradation, sediment retention, primary production and soil formation and structure, which effects may also ultimately cascade onto other taxa (Orwin et al 2016;Ferlian et al 2018;De Almeida et al 2020). However, little is known of these effects on soil fauna.…”

“…Plants also increase pore space through root growth and shoots which push the soil upwards when emerging in spring (Howison et al 2017), an impact on soil structure they share with another secondary EE, the bioturbating amphipod Orchestia gammarellus. Through digging of burrows, thereby mixing dead organic matter with mineral soil and increasing pore diameter, pore connectivity, soil moisture levels and soil aeration (Wilkinson et al 2009;Howison et al 2015), O. gammarellus potentially creates favourable conditions and habitat for Collembola (Eaton et al 2004;De Almeida et al 2020). This bioturbator is generally absent from grazed salt marshes responding to soil compaction by grazers (Schrama et al 2013), while the increase in light levels associated with short vegetation negatively affects their presence (Thakur et al 2014).…”

Temperature or competition: Which has more influence on Mediterranean ant communities?

“…Ants are one of the most abundant, successful and dominant invertebrate taxa in terrestrial ecosystems [1]. They are ecosystem engineers, capable of modifying their surrounding environment [2,3]. Their eusocial lifestyle serves as a buffer against predation and environmental stress, and thus, interspecific competition has been long considered the widespread mechanism structuring ant communities [4,5] (but see [6,7]).…”

A soil‐nesting invasive ant disrupts carbon dynamics in saplings of a foundational ant–plant

“…Plants growing near ant nests can have higher water stress (Moutinho et al, 2003), possibly because nest excavation interrupts the root's access to soil water and other nutrients. Alternatively, ants also can concentrate nutrients near their mounds by collecting litter (Cammeraat & Risch, 2008), which can improve growth of nearby woody (Lafleur et al, 2005) and non-woody plants (De Almeida et al, 2020;DeFauw et al, 2008). Thus, ant soil nesting can impose both positive and negative effects on plant growth and water relations, but more research is needed to determine how and predict if soil nesting by invasive ants will cause net gains or losses to the terrestrial carbon cycle.…”