Interactions between ants and honeydew-producing hemipteran insects are abundant and widespread in arthropod food webs, yet their ecological consequences are very poorly known. Ant–hemipteran interactions have potentially broad ecological effects, because the presence of honeydew-producing hemipterans dramatically alters the abundance and predatory behaviour of ants on plants. We review several studies that investigate the consequences of ant–hemipteran interactions as ‘keystone interactions’ on arthropod communities and their host plants. Ant–hemipteran interactions have mostly negative effects on the local abundance and species richness of several guilds of herbivores and predators. In contrast, out of the 30 studies that document the effects of ant–hemipteran interactions on plants, the majority (73%) shows that plants actually benefit indirectly from these interactions. In these studies, increased predation or harassment of other, more damaging, herbivores by hemipteran-tending ants resulted in decreased plant damage and/or increased plant growth and reproduction. The ecological consequences of mutualistic interactions between honeydew-producing hemipterans and invasive ants relative to native ants have rarely been studied, but they may be of particular importance owing to the greater abundance, aggressiveness and extreme omnivory of invasive ants. We argue that ant–hemipteran interactions are largely overlooked and underappreciated interspecific interactions that have strong and pervasive effects on the communities in which they are embedded.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2006.3701

Ecological consequences of interactions between ants and honeydew-producing insects.

We reviewed the evidence on the role of ants as plant biotic defenses, by conducting meta-analyses for the effects of experimental removal of ants on plant herbivory and fitness with data pooled from 81 studies. Effects reviewed were plant herbivory, herbivore abundance, hemipteran abundance, predator abundance, plant biomass and reproduction in studies where ants were experimentally removed (n = 273 independent comparisons). Ant removal exhibited strong effects on herbivory rates, as plants without ants suffered almost twice as much damage and exhibited 50% more herbivores than plants with ants. Ants also influenced several parameters of plant fitness, as plants without ants suffered a reduction in biomass (-23.7%), leaf production (-51.8%), and reproduction (-24.3%). Effects were much stronger in tropical regions compared to temperate ones. Tropical plants suffered almost threefold higher herbivore damage than plants from temperate regions and exhibited three times more herbivores. Ant removal in tropical plants resulted in a decrease in plant fitness of about 59%, whereas in temperate plants this reduction was not statistically significant. Ant removal effects were also more important in obligate ant-plants (=myrmecophytes) compared to plants exhibiting facultative relationships with hemiptera or those plants with extrafloral nectaries and food bodies. When only tropical plants were considered and the strength of the association between ants and plants taken into account, plants with obligate association with ants exhibited almost four times higher herbivory compared to plants with facultative associations with ants, but similar reductions in plant reproduction. The removal of a single ant species increased plant herbivory by almost three times compared to the removal of several ant species. Altogether, these results suggest that ants do act as plant biotic defenses, but the effects of their presence are more pronounced in tropical systems, especially in myrmecophytic plants.

Ants on plants: a meta-analysis of the role of ants as plant biotic defenses

Correlation between gut microbiota and host phylogeny could reflect codiversification over shared evolutionary history or a selective environment that is more similar in related hosts. These alternatives imply substantial differences in the relationship between host and symbiont, but can they be distinguished based on patterns in the community data themselves? We explored patterns of phylogenetic correlation in the distribution of gut bacteria among species of turtle ants (genus Cephalotes), which host a dense gut microbial community. We used 16S rRNA pyrosequencing from 25 Cephalotes species to show that their gut community is remarkably stable, from the colony to the genus level. Despite this overall similarity, the existing differences among species' microbiota significantly correlated with host phylogeny. We introduced a novel analytical technique to test whether these phylogenetic correlations are derived from recent bacterial evolution, as would be expected in the case of codiversification, or from broader shifts more likely to reflect environmental filters imposed by factors such as diet or habitat. We also tested this technique on a published data set of ape microbiota, confirming earlier results while revealing previously undescribed patterns of phylogenetic correlation. Our results indicated a high degree of partner fidelity in the Cephalotes microbiota, suggesting that vertical transmission of the entire community could play an important role in the evolution and maintenance of the association. As additional comparative microbiota data become available, the techniques presented here can be used to explore trends in the evolution of host-associated microbial communities.

Stability and phylogenetic correlation in gut microbiota: lessons from ants and apes

Plants secrete extrafloral nectar (EFN) as an induced defense against herbivores. EFN contains not only carbohydrates and amino acids but also pathogenesis-related proteins and other protective enzymes, making EFN an exclusive reward. EFN secretion is commonly induced after wounding, likely owing to a jasmonic acid–induced cell wall invertase, and is limited by phloem sucrose availability: Both factors control EFN secretion according to the optimal defense hypothesis. Non-ant EFN consumers include parasitoids, wasps, spiders, mites, bugs, and predatory beetles. Little is known about the relevance of EFN to the nutrition of its consumers and, hence, to the structuring of arthropod communities. The mutualism can be established quickly among noncoevolved (e.g., invasive) species, indicating its easy assembly is due to ecological fitting. Therefore, increasing efforts are directed toward using EFN in biocontrol. However, documentation of the importance of EFN for the communities of plants and arthropods in natural, invasive, and agricultural ecosystems is still limited.

Extrafloral nectar at the plant-insect interface: a spotlight on chemical ecology, phenotypic plasticity, and food webs.

Current evidence suggests that ant–plant relationships may influence species composition, abundance, and interactions at the community scale. The main resource that plants offer to ants is extrafloral nectar (EFN) and the major part of published studies shown benefits from ants to plants possessing EFNs. However, the complementary question of whether and how ants benefit from EFNs is rarely addressed. Here, we present the results of a long-term study to demonstrate whether EFN has a positive effect on ant colony fitness. We quantified colony growth rate, survival and the final weight of individuals as measures of benefit derived from EFN. Our results provide clear evidence that EFN can have a significant positive impact on the survivorship, growth and reproduction of the Myrmicinae Cephalotes pusillus. In fact, a diet rich in EFN (providing at least 30 cal per day) resulted in five times more individuals per colony, greater body weights, and more eggs. These results have shed new light on the relationships between ants and EFN-bearing plants such as in tropical and temperate systems. The ant C. pusillus is the first case in which we have firm evidence that EFN improves colony growth and development, corroborating more than 100 years of experimental evidence of benefits to plants in these widespread relationships.

/pdf/ant-plant-interaction-in-the-neotropical-savanna-direct-2xnaj6u7ag.pdf

Ant–plant interaction in the Neotropical savanna: direct beneficial effects of extrafloral nectar on ant colony fitness

The question if ant behaviour and biological limitations should be considered before generalisations about the ant’s defensive capabilities in ant–plant relationships was explored through a new experimental manipulation. In the Brazilian tropical savanna, we tested the protective action of Cephalotes pusillus Klug on the extrafloral nectar-bearing plant Ouratea spectabilis Engl. (Ochnaceae). Three treatments were performed: control (free ant access), Cephalotes-treatment (access permitted only to C. pusillus), and ant free treatment (no ants). No difference was found in the levels of leaf herbivory among experimental stems. Visitation by different ant species to control stems translated into significantly greater fruit and seed production by this stem category than by ant-free and Cephalotes-treated stems. Thus, results showed that an investigation of system’s natural history, ant’s morphological traits, defensive capabilities and behaviour are needed before a protective role is inferred to each associated ant species.

/pdf/nectar-and-pollen-gathering-cephalotes-ants-provide-no-15urngapv0.pdf

Nectar- and pollen-gathering Cephalotes ants provide no protection against herbivory: a new manipulative experiment to test ant protective capabilities

Terrestrial communities based on livingplants involve at least three interacting trophic levels: plants, herbivores, and natural enemies of herbivores. Recent studies have showed that the outcomes of these relationships are essential for understanding not only insect-plant interactions but also whole communities. Here, we present results of manipulative experiments (ant-exclusion) in the field following an ant-plant-hemipteran interaction for eight years in the same Cerrado vegetation area. We showed that the interaction results in benefits to the hemipterans in terms of high survivorship and reproduction and to the host plant in leaf herbivory reduction. The benefits are dependent of ant presence and endure through time. The studied interaction shows that this ant-hemipteran interaction is conservative in terms of maintenance of the related species and outcomes in the same geographical area.

Conservative benefits in an ant-hemipteran association in the Brazilian tropical Savanna

Este estudo aplicou tecnicas de enriquecimento ambiental em um grupo cativo de Callithrix penicillata (saguis-de-tufos-pretos) com o objetivo de aumentar o bem-estar desses animais. O enriquecimento foi realizado com seis animais, tres machos e tres femeas, do Zoologico do Parque Municipal do Sabia (Uberlândia, MG, Brasil). Os dados foram coletados em tres fases, pre-enriquecimento, enriquecimento e pos-enriquecimento, cada uma com 40h de observacoes quantitativas. Foram utilizados dois modelos de enriquecimento sensorial e quatro modelos de enriquecimento alimentar. A resposta comportamental ao enriquecimento foi positiva. Foi observado aumento em alguns comportamentos, como exploratorios, de forrageio, sociais e territoriais, ao passo que outros diminuiram como os estereotipos (indicativos de estresse). Durante e apos o enriquecimento houve exibicao de comportamentos antes nao expressos, principalmente os relacionados a reproducao e socializacao. As mudancas comportamentais observadas indicam que o enriquecimento promoveu uma melhora na qualidade de vida dos animais.

/pdf/influencia-de-tecnicas-de-enriquecimento-ambiental-no-5bur2r06rj.pdf

Jonas Byk

Papers

Ant–plant interaction in the Neotropical savanna: direct beneficial effects of extrafloral nectar on ant colony fitness

Nectar- and pollen-gathering Cephalotes ants provide no protection against herbivory: a new manipulative experiment to test ant protective capabilities

Conservative benefits in an ant-hemipteran association in the Brazilian tropical Savanna

Influência de técnicas de enriquecimento ambiental no aumento do bem-estar de Callithrix penicillata (E. Geoffroy, 1812) (Primates: Callitrichidae)

Influence of environmental enrichment techniques in improvement of welfare of Callithrix penicillata (E. Geoffroy, 1812) (Primates: Callitrichidae)