Ant body size mediates functional performance and species interactions in carrion decomposer communities

Abstract

Growing concern over rapid species declines and extinctions has led to considerable interest in the role of biodiversity for maintaining ecological processes. However, the loss of particular species has more pronounced effects on ecosystem services than others, highlighting the importance of key functional species traits and their relationships to ecosystem functioning. Human‐induced disturbances, such as species invasions, land use changes, or abiotic changes, appear to disproportionally impact larger species rather than smaller ones. The loss of large‐bodied species in the community diminishes key ecosystem services like seed dispersal, pest control, pollination and decomposition. Here, we use carrion, a nutrient‐rich ephemeral resource, to test the hypotheses that ants positively affect decomposition rates and that their role in the necrophilous community—as predator or decomposer—is mediated by body size. We further investigate the relative contribution of maggots versus ants to biomass decomposition. Our results show that ants contributed positively to the decomposition process. Moreover, decomposition was shaped by an intricate interplay between competition and predation among the guild of decomposer insects. As predicted, larger ants show a double action in increasing decomposition rate and predating on maggots, while small ants are rather inefficient decomposers and did not act as predators on other decomposer species. Our study shows that differentiating key taxonomic groups in function of their body size is key to untangle the diversity and directions of the various roles they play within complex ecological processes. Read the free Plain Language Summary for this article on the Journal blog.

Development of a new apparatus to partition ant body size reveals their respective functional role within ant communities

“…Alternatively, it may be the case that smaller species are better over larger periods of time (here we only provided 2 hours for exploitation of the resource). This hypothesis, however, may not be supported as similar findings were seen in Nooten et al (2022) during decomposition experiments with mouse carrion were used as bait for 48 hours. Interestingly, our results also showed that the large treatment had a higher M c than the full-inclusion treatment, so the addition of smaller individuals reduced the amount of resource removed, likely a consequence of interspecific competition (Slade et al, 2019) and an interesting venue for further study.…”

“…The efficacy of the exclusion design was tested a total of 26 times across 19 sites, with sites only being sampled once per year. At each site, 6 treatments were placed in a 5 x 5 m quadrat with the control and full access treatments being set in the centre (separated by at least 2 m) while the remaining four treatments were positioned randomly in one of the corners at least 3-5 m apart from each other (Nooten et al, 2022). This reduced interference between treatments as most ground foraging ants in tropical Asia don't forage more than 1 m from their nest (Eguchi et al, 2004, unpublished results).…”

“…2-5 individuals of each species were selected at random for morphological measurements. If 5 individuals of a species were not collected from the treatments, measurements were supplemented with individuals collected from Winkler samples at sites in 2019 (Nooten et al, 2022) or from the HKU IBBL collection. All species collected except Camponotus jianghuaensis had at least two individuals and were included in the statistical tests.…”

The role of body mass in limiting post heat‐coma recovery ability in terrestrial ectotherms

“…Ants (Formicidae) have been widely used as an ectothermic model in thermal biology due to their biological and habitat diversity (Cerdá et al, 1998; Kaspari et al, 2015; Leong et al, 2022), and variations in body mass are often associated with the ecosystem functions they perform (Nooten et al, 2022; Séguin et al, 2014; Woodward et al, 2005). To understand the benefit of post heat‐coma recovery, we first validated the fate of heat‐comatose ant individuals in the field to test if heat‐coma condition is considered as “ecological death” (Angilletta Jr, 2009; Jørgensen et al, 2020).…”

Territorial ants delay carrion decomposition by depressing Diptera larvae in a Tibetan alpine meadow

“…Meanwhile, they were also observed to accelerate the carcass decomposition rate by directly feeding on the carrion tissues or by creating holes that could favour the action of other organisms (Campobasso et al, 2009; Eubanks et al, 2019; Paula et al, 2016). In addition, the role of ants on carrion decomposition is recently demonstrated to be mediated by their body size, that is, larger ants increase decomposition rate despite their predation on maggots, and small ants have little effects on carrion decomposition (Nooten et al, 2022). Therefore, the effect sign and strength of even one specific decomposer guild on carrion decomposition seem to be largely context‐dependent.…”