Prevalence and impact of a virulent parasite on a tripartite mutualism

Currie, Cameron R.

doi:10.1007/s004420100630

Cited by 125 publications

(154 citation statements)

References 31 publications

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“…The colonies were maintained as described in Bot and Boomsma (1996). They were all healthy and had accumulated fungus over the months immediately prior to the study, suggesting that they were free of infection by the parasite Escovopsis (Currie, 2001b). Fungus gardens (1-2 per colony) were built under inverted 1 litre beakers and were thus cylindrical.…”

Section: Methodsmentioning

confidence: 99%

Mutualistic bacteria and a possible trade-off between alternative defence mechanisms in Acromyrmex leaf-cutting ants

et al. 2002

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Summary. Leaf-cutting ants in the genus Acromyrmex are obligately dependent upon a mutualistic fungus as their primary food source. One mechanism employed by fungusgrowing ants to control general infections of the fungus garden is through secretions of the metapleural glands, which produce a broad spectrum of antibiotics. In addition, the ants carry a mutualistic filamentous bacterium (an actinomycete) on their cuticle, which produces antibiotics that suppress the growth of Escovopsis, a specialised parasite of the gardens of fungus-growing ants . We show that a clear trade-off between these defence mechanisms exists at the level of individual workers. Major workers have relatively small metapleural glands, proportional to body size, have a high abundance of the mutualistic bacterium, and are, when carrying the bacterium, most abundant in the lower part of the fungus garden, where Escovopsis, if present, is also most abundant. Minor workers have relatively large metapleural glands, proportional to body size, but have a relatively low abundance of the bacterium and are most abundant at the top of the fungus garden, where a variety of potentially infectious microbes enter the colony on the substrate used to grow the fungal mutualist. The two sympatric species investigated, Acromyrmex octospinosus and A. echinatior, have quantitatively different combinations of these defence mechanisms, suggesting that the optimal investment in alternative defence mechanisms in different ant species depends on differences in caste allocation or parasite pressure.

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Section: Methodsmentioning

confidence: 99%

Mutualistic bacteria and a possible trade-off between alternative defence mechanisms in Acromyrmex leaf-cutting ants

et al. 2002

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“…1A) (7), which have evolved in association with the ants and their cultivated fungi (8). Escovopsis infection can have detrimental impacts on garden health and, consequently, on the survival of ant colonies (9,10). Such mycoparasitism, the phenomenon whereby one fungus is parasitic on another fungus, is rare.…”

mentioning

confidence: 99%

Small genome of the fungus Escovopsis weberi , a specialized disease agent of ant agriculture

Man

Stajich

Kubicek

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Many microorganisms with specialized lifestyles have reduced genomes. This is best understood in beneficial bacterial symbioses, where partner fidelity facilitates loss of genes necessary for living independently. Specialized microbial pathogens may also exhibit gene loss relative to generalists. Here, we demonstrate that Escovopsis weberi, a fungal parasite of the crops of fungus-growing ants, has a reduced genome in terms of both size and gene content relative to closely related but less specialized fungi. Although primary metabolism genes have been retained, the E. weberi genome is depleted in carbohydrate active enzymes, which is consistent with reliance on a host with these functions. E. weberi has also lost genes considered necessary for sexual reproduction. Contrasting these losses, the genome encodes unique secondary metabolite biosynthesis clusters, some of which include genes that exhibit up-regulated expression during host attack. Thus, the specialized nature of the interaction between Escovopsis and ant agriculture is reflected in the parasite’s genome.

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“…However, the phylogenies do not mirror one another perfectly because of periodic switching of fungi between unrelated host lineages. Although mechanisms governing host-switching are not well understood, parasitoid wasps or mites are thought to play a role in dispersing fungi between host lineages (11,12). Transport of one species by another, known as phoresis (13), is another way in which members of a broad community can conceivably alter patterns of coevolutionary history (14,15).…”

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confidence: 99%

Community interactions govern host-switching with implications for host–parasite coevolutionary history

Harbison

Clayton

2011

Proc. Natl. Acad. Sci. U.S.A.

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Reciprocal selective effects between coevolving species are often influenced by interactions with the broader ecological community. Community-level interactions may also influence macroevolutionary patterns of coevolution, such as cospeciation, but this hypothesis has received little attention. We studied two groups of ecologically similar feather lice (Phthiraptera: Ischnocera) that differ in their patterns of association with a single group of hosts. The two groups, "body lice" and "wing lice," are both parasites of pigeons and doves (Columbiformes). Body lice are more host-specific and show greater population genetic structure than wing lice. The macroevolutionary history of body lice also parallels that of their columbiform hosts more closely than does the evolutionary history of wing lice. The closer association of body lice with hosts, compared with wing lice, can be explained if body lice are less capable of switching hosts than wing lice. Wing lice sometimes disperse phoretically on parasitic flies (Diptera: Hippoboscidae), but body lice seldom engage in this behavior. We tested the hypothesis that wing lice switch host species more often than body lice, and that the difference is governed by phoresis. Our results show that, where flies are present, wing lice switch to novel host species in sufficient numbers to establish viable populations on the new host. Body lice do not switch hosts, even where flies are present. Thus, differences in the coevolutionary history of wing and body lice can be explained by differences in host-switching, mediated by a member of the broader parasite community.coevolutionary biology | community ecology | phoresy | ectoparasites

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Prevalence and impact of a virulent parasite on a tripartite mutualism

Cited by 125 publications

References 31 publications

Mutualistic bacteria and a possible trade-off between alternative defence mechanisms in Acromyrmex leaf-cutting ants

Mutualistic bacteria and a possible trade-off between alternative defence mechanisms in Acromyrmex leaf-cutting ants

Small genome of the fungus Escovopsis weberi , a specialized disease agent of ant agriculture

Community interactions govern host-switching with implications for host–parasite coevolutionary history

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