Caterpillars and Fungal Pathogens: Two Co-Occurring Parasites of an Ant-Plant Mutualism

Abstract

In mutualisms, each interacting species obtains resources from its partner that it would obtain less efficiently if alone, and so derives a net fitness benefit. In exchange for shelter (domatia) and food, mutualistic plant-ants protect their host myrmecophytes from herbivores, encroaching vines and fungal pathogens. Although selective filters enable myrmecophytes to host those ant species most favorable to their fitness, some insects can by-pass these filters, exploiting the rewards supplied whilst providing nothing in return. This is the case in French Guiana for Cecropia obtusa (Cecropiaceae) as Pseudocabima guianalis caterpillars (Lepidoptera, Pyralidae) can colonize saplings before the installation of their mutualistic Azteca ants. The caterpillars shelter in the domatia and feed on food bodies (FBs) whose production increases as a result. They delay colonization by ants by weaving a silk shield above the youngest trichilium, where the FBs are produced, blocking access to them. This probable temporal priority effect also allows female moths to lay new eggs on trees that already shelter caterpillars, and so to occupy the niche longer and exploit Cecropia resources before colonization by ants. However, once incipient ant colonies are able to develop, they prevent further colonization by the caterpillars. Although no higher herbivory rates were noted, these caterpillars are ineffective in protecting their host trees from a pathogenic fungus, Fusarium moniliforme (Deuteromycetes), that develops on the trichilium in the absence of mutualistic ants. Therefore, the Cecropia treelets can be parasitized by two often overlooked species: the caterpillars that shelter in the domatia and feed on FBs, delaying colonization by mutualistic ants, and the fungal pathogen that develops on old trichilia. The cost of greater FB production plus the presence of the pathogenic fungus likely affect tree growth.

Ants suppressing plant pathogens: a review

“…Additionally, there was reason to believe that two pairs of studies could have reported on the same species combinations. One of the combinations reported by González-Teuber and Heil (2010) could be identical to one of the combinations examined in Gonzalez-Teuber et al (2014) and, secondly, Roux et al (2011) and Belin-Depoux et al (1997) reported on identical plant-pathogen combinations with the only difference that one of two excluded ant species was different. If the common ant species was responsible for the observed effect, the two studies would have identical combinations.…”

“…Another myrmecophyte, Cecropia obtuse, also showed reduced fungal infections when inhabited by its obligate ant partners Azteca alfari and A. ovaticeps (Roux et al 2011). Among treelets inhabited by Azteca ants, the percentage of plants infected by the fungi Fusarium moniliforme was more than five-fold lower than on un-inhabited plants.…”

Wood Ant (Formica polyctena) Services and Disservices in a Danish Apple Plantation

“…There can be several mechanisms behind pathogen protection. For example, ants may inhibit plant pathogens by eating fungal spores (Letourneau, 1998;Thornham et al, 2011), excreting antibiotics (Peng & Christian, 2005;Gonzalez-Teuber et al, 2014) or by deterring diseases vectors (Letourneau, 1998;Roux et al, 2011). Taken together, the provision of these three types of services may lead to highly effective ant-based biocontrol programs.…”

Bacterial Carbonic Anhydrases as Drug Targets

“…Prokaryotes include several kinds of microorganisms, such as archaea, bacteria, and cyanobacteria (7). Most such microorganisms do not normally cause disease in humans, existing either in a state of commensalism or in mutualism with the host (8)(9)(10). This nonharmful condition occurs when the immune system works well, but the same organisms can cause infection when the latter fails.…”