Myrmecophily
As a result, ants play a key role in controlling arthropod richness, abundance, and community structure.
[9] Some myrmecophilous beetles are in the families Coccinellidae (e.g. the ladybird Thalassa saginata), Aphodiidae, Scarabaeidae, Lucanidae, Cholevidae, Pselaphidae, Staphylinidae, Histeridae, and Ptiliidae (some treated here as subfamilies).
[10][better source needed] Myrmecophilous associations are also seen in various other insects, such as aphids and treehoppers, as well as the hoverfly genus Microdon and several other groups of flies.
If the infiltrating species' impact is too negative on the colony, they risk discovery; this usually results in relatively small populations of myrmecophiles.
[17] Beltian bodies provide a high-energy food source to ants in the form of nutritive corpuscles produced on leaflet tips,[1] and they have been described in at least 20 plant families.
[17] EFNs being outside of the plant flowers are not employed in pollination; their primary purpose is to attract and sustain tending ants.
[3][16] This system was studied by Daniel Janzen in the late 1960s, who provided some of the first experimental evidence that ants significantly reduce herbivory rates of myrmecophytes.
[1] For many plants, including the bullhorn acacias, ants can significantly reduce herbivory from both phytophagous insects and larger organisms, such as large grazing mammals.
[3] Myrmecophily is considered a form of indirect plant defense against herbivory, though ants often provide other services in addition to protection.
Some ants provide hygienic services to keep leaf surfaces clean and deter disease, and defense against fungal pathogens has also been demonstrated.
Mites are particularly adept at being myrmecophiles, being that they are small enough to enter nests easily and to not be evicted from the homes and bodies of ants.
[23] These types of ant-insect interactions involve the ant providing some service in exchange for nutrients in the form of honeydew, a sugary fluid excreted by many phytophagous insects.
Some beetles from the family Coccinellidae have developed behaviors, body shapes, and chemical mimicry to prey on ant-tended aphids.
The tending ants ingest these honeydew droplets, then return to their nest to regurgitate the fluid for their nestmates (see trophallaxis).
[1] Between 90 and 95% of the dry weight of aphid honeydew is various sugars, while the remaining matter includes vitamins, minerals, and amino acids.
[25] The secretions of Narathura japonica caterpillars are thought to be more than merely providing nutrition, with components that cause behavior alteration in the ants, with a reduction in the locomotory activity of caterpillar attendants, increased aggression and protectiveness by Pristomyrmex punctatus ants, suggesting that the association are better treated as parasitic than mutualistic.
For example, some plants host aphids instead of investing in EFNs, which may be more energetically costly depending on local food availability.
[33][34] Combined with the fact that ants are one of the most dominant lifeforms on earth,[16] myrmecophily clearly plays a significant role in the evolution and ecology of diverse organisms, and in the community structure of many terrestrial ecosystems.
Analyses of phylogenetic information for myrmecophilous organisms, as well as ant lineages, have demonstrated that myrmecophily has arisen independently in most groups several times.
Because multiple gains (and perhaps losses) of myrmecophilous adaptations have happened, the evolutionary sequence of events in most lineages is unknown.
In studying the coevolution of myrmecophilous organisms, many researchers have addressed the relative costs and benefits of mutualistic interactions, which can vary drastically according to local species composition and abundance, variation in nutrient requirements and availability, host plant quality, presence of alternative food sources, abundance and composition of predator and parasitoid species, and abiotic conditions.
[33] In many cases, variation in external factors can result in interactions that shift along a continuum of mutualism, commensalism, and even parasitism.
This asymmetry leads to "cheating", in which one partner evolves strategies to receive benefits without providing services in return.
[33] One of the most obvious ways in which myrmecophily influences community structure is by allowing for the coexistence of species that might otherwise be antagonists or competitors.
[5] At both small and large spatiotemporal scales, mutualistic interactions influence patterns of species richness, distribution, and abundance.
[17] Furthermore, by providing associational refugia and habitat amelioration for many species, ants are considered dominant ecosystem engineers.
[3][35] Myrmecophilous interactions provide an important model system for exploring ecological and evolutionary questions regarding coevolution, plant defense theory, food web structure, species coexistence, and evolutionarily stable strategies.
