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Abstract Fungus‐farming ants (Hymenoptera: Formicidae) have become model systems for exploring questions regarding the evolution of symbiosis. However, robust phylogenetic studies of both the ant agriculturalists and their fungal cultivars are necessary for addressing whether or not observed ant–fungus associations are the result of coevolution and, if so, whether that coevolution has been strict or diffuse. Here we focus on the evolutionary relationships of the species within the ant genusMyrmicocryptaand of their fungal cultivars. The fungus‐farming ant genusMyrmicocryptawas created by Fr. Smith in 1860 based on a single alate queen. Since then, 31 species and subspecies have been described. Until now, the genus has not received any taxonomic treatment and the relationships of the species within the genus have not been tested. Our molecular analyses, using ∼40 putative species and six protein‐coding (nuclear and mitochondrial) gene fragments, recoverMyrmicocryptaas monophyletic and as the sister group of the genusMycocepurusForel. The speciesM. tuberculataWeber is recovered as the sister to the rest ofMyrmicocrypta. The time‐calibrated phylogeny recovers the age of stem groupMyrmicocryptaplus its sister group as 45 Ma, whereas the inferred age for the crown groupMyrmicocryptais recovered as 27 Ma. Ancestral character‐state analyses suggest that the ancestor ofMyrmicocryptahad scale‐like or squamate hairs and that, although such hairs were once considered diagnostic for the genus, the alternative state of erect simple hairs has evolved at least seven independent times. Ancestral‐state analyses of observed fungal cultivar associations suggest that the most recent common ancestor ofMyrmicocryptacultivated clade 2 fungal species and that switches to clade 1 fungi have occurred at least five times. It is our hope that these results will encourage additional species‐level phylogenies of fungus‐farming ants and their fungal cultivars, which are necessary for understanding the evolutionary processes that gave rise to agriculture in ants and that produced the current diversity of mutualistic ant–fungus interactions.
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The Last Piece of the Puzzle? Phylogenetic Position and Natural History of the Monotypic Fungus-Farming Ant Genus Paramycetophylax (Formicidae: Attini)
Abstract The evolutionary history of fungus-farming ants has been the subject of multiple morphological, molecular phylogenetic, and phylogenomic studies. Due to its rarity, however, the phylogenetic position, natural history, and fungal associations of the monotypic genus Paramycetophylax Kusnezov have remained enigmatic. Here we report the first excavations of colonies of Paramycetophylax bruchi (Santschi) and describe its nest architecture and natural history. Utilizing specimens from these collections, we generated ultraconserved-element (UCE) data to determine the evolutionary position of Paramycetophylax within the fungus-farming ants and ribosomal ‘fungal barcoding’ ITS sequence data to identify the fungal cultivar. A maximum-likelihood phylogenomic analysis indicates that the genus Paramycetophylax is the sister group of the yeast-cultivating Cyphomyrmex rimosus group, an unexpected result that renders the genus Cyphomyrmex Mayr paraphyletic. A Bayesian divergence-dating analysis indicates that Paramycetophylax diverged from its sister group around 36 mya (30–42 mya, HPD) in the late Eocene-early Oligocene, a period of global cooling, expansion of grasslands, and large-scale extinction of tropical organisms. Bayesian analysis of the fungal cultivar ITS gene fragment indicates that P. bruchi practices lower agriculture and that the cultivar grown by P. bruchi belongs to the Clade 1 group of lower-attine fungi, a clade that, interestingly, also includes the C. rimosus-group yeast cultivars. Based on these results, we conclude that a better understanding of P. bruchi and its fungal cultivar, including whole-genome data, is critical for reconstructing the origin of yeast agriculture, a major transition in the evolution of fungus-farming ants.
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- Award ID(s):
- 1927161
- PAR ID:
- 10349172
- Editor(s):
- Camacho, Gabriela P
- Date Published:
- Journal Name:
- Insect Systematics and Diversity
- Volume:
- 6
- Issue:
- 1
- ISSN:
- 2399-3421
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/isd/ixab029
