Attine-fungus mutualism: Prophylactic behavior, parasites and use of antibiotics.

摘要

My dissertation describes aspects of the natural history of fungus growing ants and explains how these ants integrate behavior with the use of antibiotics from metapleural gland (MG) secretions to defend again infectious diseases and cosmopolitan contaminants. In addition, I also report the prevalence of Diapriinae parasitoids, minute wasps that attack a fungus-growing ant. Following an introductory chapter, in Chapter 2 I describe nest foundation in Acromyrmex octospinosus including: (i) ontogenetical and demographical information, (ii) putative prophylactic behaviors that could explain alternative strategies of diseases managements, as well as (iii) active use of MG, and (iv) isolation of the incipient fungus garden on rootlets. In Chapters 3 and 4, I study how ants and particularly the fungus growing ants actively use their MG in grooming. I found that a wide number of ant species use the MG during their hygienic grooming. Moreover, active use of MG grooming was shown in higher attines (Atta, Acromyrmex, Sericomyrmex and Trachymyrmex) and Cyphomyrmex in response to experimental inoculations with common pathogenic fungi. This indicates that ants have total control over when and how thy use their antimicrobial secretions. These results are very different from previous suggestions that transference of MG secretions is passive, and that ants do not have control over when they use their MG secretions. I present information in Chapter 5 to show a trade-off at the genus level between the presences of mutualistic Actinomycete bacteria for combating fungal pathogens vs. MG grooming across eight species of attines. Previous research had suggested that all attines possessed mutualistic bacteria, whose metabolites function as antibiotics specific to control of a fungal garden parasite, Escovopsis sp., but my research shows that some species do not have the mutualistic bacteria and employ MG grooming instead. In Chapter 6, I describe for the first time the prevalence and intensity of parasitism by diapriid wasps attacking a fungus-growing ant. I report that Acanthopria and Mimopriella, two Diapriinae genera, parasitize from 0--100% of the ant larvae of Cyphomyrmex minutus and Cyphomyrmex rimosus, and over 70% of colonies were parasitized. Diapriinae wasps are abundant, but their biology is very little known. The parasitic interaction between attine ants and diapriines wasps represents a new area of study.