Abstract1. Nutrient supplies to plants from ants are well known from specialised myrmecophytic symbioses and from plants growing in soil close to ant nests. However, above-ground nutrient pathways may play a largely unrecognised role also in less specialised ant-plant interactions-the numerous facultative relationships, where ants forage on plants.2. In a laboratory experiment, weaver ants (Oecophylla smaragdina) were confined to the canopies of coffee (Coffea arabica) seedlings, excluding any ant-to-plant transfer of nutrients via the soil strata. When ants were fed 15 N-labelled glycine and subsequently deposited faecal droplets on the seedlings, coffee leaves showed increased levels of 15 N and total nitrogen compared to control plants without ants. This was evident for both exposed leaves and leaves covered in plastic bags (i.e. not directly exposed to ants). Thus, nitrogen from ant excretions was absorbed through the coffee leaves, and subsequently, translocated within the plants and possibly leading to the observed higher shoot/root (wet weight) ratios observed on ant-plants compared to controls.3. Synthesis. These results reveal an undescribed foliar uptake of ant-provided nutrients. If this is a general mechanism, a vast amount of ant-plant interactions involves fertilisation. Foliar fertilisation by ants may be an important steady benefit to plants, which has driven the evolution of ant-plant mutualisms in parallel with the well-recognised but probably more fluctuating benefit from herbivore protection. Given the world-wide abundance of plant canopies foraged by ants, this nutrient pathway may be of high ecological significance. K E Y W O R D S 15N uptake, ant faecal droplets, ant-plant interaction, Coffea arabica, foliar fertilisation, nitrogen, Oecophylla smaragdina | INTRODUCTIONAnt-plant mutualisms range from facultative interactions, where plants interact with multiple ant species, to obligate one-to-one interactions, which tend to be species specific (Heil & McKey, 2003). These relationships involve plant-provided resources for ants (nesting space and food), which, in return, defend the plant against herbivory. Recent meta-analyses of ant-plant mutualisms support that ants lead to increased plant fitness (Chamberlain & Holland, 2009;Rosumek et al., 2009;Trager et al., 2010). However, ant-mediated reductions in herbivory do not always fully explain the improvements observed in plant performance, e.g. growth and reproduction (Chamberlain & Holland, 2009;Trager et al., 2010). This suggests that mechanisms other than herbivore protection benefit host plants. Such mechanisms may include nutrient fluxes from ants to plants. | Journal of Ecology PINKALSKI et AL.Transfer of nutrients from ants to plants is known from myrmecophytic plants that provide specialised domatia where ants can nest (Gegenbauer, Mayer, Zotz, & Richter, 2012;Solano & Dejean, 2004;Treseder, Davidson, & Ehleringer, 1995). In myrmecophytes, as much as 80% of plant nitrogen (N) acquisition may derive from ant debris and excretory deposi...

In most ecosystems, ants are a dominant part of the arthropod community. A thorough understanding of their ecological impact, however, has been hampered by limited availability of data on ant abundance. Therefore, we developed a method allowing quick and non‐destructive estimates of the biomass of Oecophylla smaragdina colonies in mango plantations. The method was based on assessments of ant nest volume in relation to ant trail density and biomass content in relation to nest volume. The relationships between these variables were modelled using Bayesian latent variable models. The resulting models predicted ant biomass from ant trail activity with a maximum uncertainty of approximately 75% of the predicted value. Five O. smaragdina colonies assessed in a mango plantation, ranged in size from 0.67 to 2.98 kg total ant biomass (fresh wt) and 84.578–376.635 workers for the smallest and largest colony respectively. Correspondingly, the density of ants in the plantation was 254 workers m−2 and a total biomass of 2.0 g ant fresh wt m−2. With this proposed method, estimates of O. smaragdina abundance can be obtained non‐destructively with a minimum of workload and it enables the scaling up of physiological experiments on per capita rates. Thus, O. smaragdina can serve as a model species providing information on the impact of ants in tropical ecosystems.

Ants are functionally important organisms in most terrestrial ecosystems. Being ubiquitous and abundant, ant communities can affect the availability of resources to both primary and secondary consumers. As nitrogen is a limiting nutrient for plant growth in most terrestrial ecosystems, deposition of ant manure may augment the host plants' acquisition of nitrogen. In this study, we quantified the manure deposited by colonies of the Asian weaver ant Oecophylla smaragdina. We developed a method to estimate the amount of manure deposited in host trees (Mangifera indica) based on the trail activity of O. smaragdina. The rate of manure deposition was on average 62.3 kg dw ha -1 y -1 , of which 0.2 kg ha -1 y -1 was deposited as urea-N, a nutrient that may be absorbed directly through the leaves, and 1.9 kg ha -1 y -1 was deposited as total nitrogen. Furthermore, ants given access to sucrose solution increased their rate of manure deposition significantly, suggesting that nectaries and/or trophobionts may play a major role in the production of ant manure. This study reveals that O. smaragdina can supply a significant amount of nitrogen to their host plants. In light of their remarkable abundance, the manure deposition by ants may have a hitherto unappreciated impact on the allocation of nutrients within their ecosystem.

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