Biology subjects

Schiott, M.

Publications and source records attributed to Schiott, M..

4 recordsLinked to original sources

bioRxiv2026

Population genomics of the inquiline social parasite Acromyrmex insinuator and its leaf-cutting ant hosts A. echinatior and A. octospinosus reveals cryptic differentiation and reduced efficiency of selection in the parasite

Inquiline social parasites usurp colonies of closely related host ants to exploit their social resources. They are almost invariably rare, patchily distributed and difficult to study. Here we build on almost 25 years of Panamanian fieldwork on the social parasite Acromyrmex insinuator and its A. echinatior and A. octospinosus hosts, to perform a population genomic analysis to test hypotheses that have been suggested to shape the evolution of inquiline social parasites: 1. Do these parasites indeed have extremely reduced effective population size? 2. Does extant genetic variation at coding and non-coding sites carry signatures of erosion of adaptive potential? 3. Has A. insinuator become fully reproductively isolated from its sympatric hosts and how closely related are its primary and secondary host? We show that the two host species are completely distinct and that genetic diversity and effective population size of the social parasite are dramatically reduced despite ongoing but very minor recent gene flow between the parasite and its primary host A. echinatior. We also demonstrate that non-synonymous codon-sites evolved at rates nearly indistinguishable from synonymous codon-sites. This indicates a significant reduction in the efficiency of natural selection consistent with inquiline social parasite lineages generally being evolutionarily short-lived. We finally uncover clear sub-structure in the parasite population, with two genetically distinct lineages occurring in sympatry in the Panama Canal Zone, and with significant differences in their likelihood of exploiting the secondary host A. octospinosus and the primary host from which they segregated sympatrically ca. 1 MYA.

genomics↗

bioRxiv2020

Proteomics reveals synergy in biomass conversion between fungal enzymes and inorganic Fenton chemistry in leaf-cutting ant colonies

The herbivorous symbiosis between leaf-cutting ants and fungal cultivars processes biomass via ant fecal fluid mixed with munched plant substrate before fungal degradation. Here we present a full proteome of the fecal fluid of Acromyrmex leaf-cutting ants, showing that most proteins function as biomass degrading enzymes and that ca. 80% are produced by the fungal cultivar and ingested, but not digested, by the ants. Hydrogen peroxide producing oxidoreductases were remarkably common in the fecal proteome, inspiring us to test a scenario in which hydrogen peroxide reacts with iron in the fecal fluid to form reactive oxygen radicals after which oxidized iron is reduced by other fecal-fluid enzymes. Our biochemical assays confirmed that these cyclical Fenton reactions do indeed take place in special substrate pellets, presumably to degrade recalcitrant lignocellulose. This implies that the symbiosis manages a combination of chemical and enzymatic degradation, an achievement that surpasses current human bioconversion technology.

ecology↗

bioRxiv2018

The origin of fungi-culture in termites was associated with a shift to a mycolytic gut bacteria community

Termites forage on a range of substrates, and it has been suggested that diet shapes the composition and function of termite gut bacterial communities. Through comparative analyses of gut metagenomes in nine termite species with distinct diets, we characterise bacterial community compositions and identify biomass-degrading enzymes and the bacterial taxa that encode them. We find that fungus-growing termite guts are enriched in fungal cell wall-degrading and proteolytic enzymes, while wood-feeding termite gut communities are enriched for plant cell wall-degrading enzymes. Interestingly, wood-feeding termite gut bacteria code for abundant chitinolytic enzymes, suggesting that fungal biomass within the decaying wood likely contributes to gut bacteria or termite host nutrition. Across diets, the dominant biomass-degrading enzymes are predominantly coded for by the most abundant bacterial taxa, suggesting tight links between diet and gut community composition, with the most marked shift being the communities coding for the mycolytic capacity of the fungus-growing termite gut.

ecology↗

bioRxiv2018

Experimental demonstration that screening can enable the environmental recruitment of a defensive microbiome

Many animals and plants recruit beneficial microbes from the environment, enhancing their defence against pathogens. However, we have only a limited understanding of the assembly mechanisms involved. A game-theoretical concept from economics, screening, potentially explains how a host selectively recruits mutualistic microbes from the environment by fomenting and biasing competition among potential symbionts in such a way that the more likely winners are antibiotic producers. The cuticular microbiomes of Acromyrmex leaf-cutting ants inspired one of the first applications of screening theory, and here we simulate this system in vitro to test screening. On agar infused with antibacterial metabolites from Acromyrmexs vertically transmitted Pseudonocardia bacteria, we show that antibiotic-producing Streptomyces bacteria exhibit higher growth rates than do non-antibiotic-producer strains and are more likely to win in direct competition. Our results demonstrate how game-theoretical concepts can provide powerful insight into host-microbiome coevolution.

evolutionary biology↗