Abstracts (first author)
Specificity and transmission of bacterial endosymbionts in Megalomyrmex social parasites and their fungus-growing ant hostsPDF
Communities or single lineages of bacterial symbionts are increasingly recognized as major fitness determinants of insects, and they are particularly likely to be mutualists when host diets are specialized and partially deficient. Some insect hosts have independently domesticated related microbes to meet similar challenges, but whether hosts with different life histories can maintain the same symbionts merely by sharing the same food niche has not been explicitly investigated. The nest-sharing symbiosis between Megalomyrmex social parasites (Formicidae: Solenopsidini) and their fungus-growing ant hosts (Formicidae: Attini) provides a unique opportunity to address this question, as both lineages rely on the same narrow fungal diet, but are only distantly related. We used a combination of 454 pyrosequencing and diagnostic PCR screening to map the diversity of bacteria associated with Megalomyrmex ants across their phylogenetic tree, which also contains clades of free-living generalist predators. We show that a specific group of Entomoplasmatales is associated with socially parasitic ‘thief-ant’, ‘agropredator’ and ‘guest-ant’ lineages of Megalomyrmex and appears to be derived from and always shared with the attine host ants. Moreover, the microbiotas of guest-ants appear to be completely dominated by a specific Bartonellaceae lineage, which can but does not need to be accompanied by the Entomoplasmatales bacteria. Bartonellaceae are native to the guest-ants and are secondarily transmitted to some (ca 40%) but not all host colonies. Our results suggest that host and socially parasitic ants contribute their own vertically transmitted bacteria to their permanent symbiosis and that these bacteria can be asymmetrically transmitted to the partner species via the fungus-garden that they share. The function of these endosymbionts remains unknown.