Experiments with artificial nests provide evidence for ant community stratification and nest site limitation in a tropical forest

Abstract

Ants are dominant in tropical forests and many species nest in hollow cavities. The manner in which species are vertically stratified in these complex habitats is not known, with lack of nest sites being proposed to limit ant populations. Here, we assess ant community stratification and nest site limitation in a lowland rainforest in New Guinea using experimental addition of artificial bamboo nests of two cavity sizes (small: ~12 mm large: ~32 mm diameter) placed at ground level, in the understorey, and in the canopy. We also conducted a pilot experiment to test the utility of nest translocation. Nests were checked for occupancy after 10 weeks and half of the occupied nests were then translocated between forest plots, while keeping same vertical position. Occupancy of small nests was much higher in the understorey and canopy than at ground level (~75% vs. ~25%). Translocation was successful, as a majority of nests was inhabited by the same species before and after translocation and there was no impact of translocation to a different plot compared to the control, except for a reduction in colony size at ground level. Our experiment demonstrates a vertical stratification in community composition of ants nesting in hollow dead cavities and shows that these ants are more nest site limited in the higher strata than at ground level. Use of small artificial cavities has great potential for future experimental studies, especially for those focused on arboreal ants, as occupancy is high and translocation does not negatively affect their colony size. Abstract in Tok Pisin is available with online material.

Spatial covariance of herbivorous and predatory guilds of forest canopy arthropods along a latitudinal gradient

“…For example Klimes et al (2011) showed that manipulative experiments of arthropods are feasible at the whole‐forest plot level, and Mottl et al . (2020) found that tropical ants were limited by nest site availability (i.e. resource availability) by manipulating artificial nests.…”

Environmental drivers of ant dominance in a tropical rainforest canopy at different spatial scales

“…However, in some cases, peripheral zones at different heights in the crown may experience similar wind and sunlight conditions as the top of the tree (Johansson, 1974). This non‐homogeneous distribution of abiotic conditions and resources affects ant foraging (Tanaka et al ., 2010; Yusah & Foster, 2016; Mottl et al ., 2019) depending on the characteristics of the individual species and which vertical strata it occupies, for instance, the understory or canopy (Spicer et al ., 2017). Thus, different ant species are expected to forage in different conditions at the micro‐scale (i.e., in terms of locations within trees and branch characteristics) within the tree crown.…”

Nesting of arboreal ants (Hymenoptera: Formicidae) in artificial substrates in coffee plantations in the Colombian Andes

“…Low colonization percentages also occurred in the same region where Vidal-Hernandez and Armbrecht (2009) found colonization values of 13.24% and 6.03% in artificially added bamboo twigs both in shade-grown and sun-grown coffee, respectively. The percentage of colonization was low compared to other studies (Hosang et al, 2010;Mottl et al 2019), possibly due to a reduction in ant diversity and abundance with elevation (Lach et al, 2010). Although ants are found on almost all continents (except Antarctica), they are mainly found at low latitudes and, in general, there is a monotonal reduction of ant richness with altitude (Fisher, 2010).…”

“…Hosang et al (2010) managed to enhance the predator ant Dolichoderus thoracicus using artificial nesting substrates while De la Mora et al (2015) found that prey removal by ants on coffee plantations was positively correlated with hollow coffee twigs. Further, heterogeneous nesting resources (substrates) could be important in promoting ant diversity and abundance (Armbrecht et al 2004;Mottl et al, 2019) Given these studies and the potential of ants as biocontrol agents, an assessment is needed for the type of substrates or the appropriate configurations required to favour ant colonization in a given agroecosystem.…”