Specificity of the parasite Escovopsis among two sympatric species of Cyphomyrmex fungus-growing ants Open Access

Chiang, Stephanie SueLing (2010)

Permanent URL: https://etd.library.emory.edu/concern/etds/73666503s?locale=en


Specificity of the parasite Escovopsis among two sympatric species of Cyphomyrmex
fungus-growing ants
By Stephanie Chiang

The fungus-growing ant system consists of four well-studied symbionts: the ants,
their cultivated fungi, mutualistic antifungal-producing actinomycete bacteria, and the
obligate parasite, Escovopsis. Escovopsis strains have evolved to evade the defenses of
only a limited range of host cultivars, thus, Escovopsis strains from one type of cultivar
often cannot infect a different type of cultivar. There is a broad scale pattern of specificity
between different clades of Escovopsis and cultivar that suggests specialization of the
parasite. In this study, we focus on the microbes associated with two sympatric species of
fungus growing ants, Cyphomyrmex longiscapus and C. muelleri, and their associated
Escovopsis strains; these species of ants are closely related but have distantly related,
morphologically distinct cultivar types. Previous garden infections have shown that
Escovopsis strains from C. muelleri and C. longiscapus systems are able to occasionally
infect atypical cultivars within the Cyphomyrmex system. To determine the potential for
host switching between C. longiscapus and C. muelleri cultivars and their associated
Escovopsis strains, we performed in vitro bioassays to examine the interactions between
the cultivars and their typical Escovopsis strains versus their interactions with atypical
Escovopsis strains from the other colony. Both host specialization and a potential for
host-switching were demonstrated both through these in vitro bioassays and through
phylogenetic analyses of Escovopsis isolates. Extending on previous phylogenetic
analyses of Cyphomyrmex Escovopsis, additional sampling here supports previous
findings of two main Escovopsis clades but suggests that one clade is less host-specific
than previously assumed. Bioassays support that the two phylogenetically distinct clades
of Cyphomyrmex-associated Escovopsis are generally specialized to utilize different hosts
but that likelihood of a given Escovopsis strain being able to establish infection of a given
host is dependent on genotype-genotype interactions between the host-parasite pair.

Table of Contents

Table of Contents

1. Introduction- pg. 1
1.1 Figure 1- pg. 7
1.2 Figure 2- pg. 8
1.3 Figure 3- pg. 10

2. Methods- pg. 12
2.1 Figure 4- pg. 14
2.2 Figure 5- pg. 14

3. Results- pg. 18
3.1 Figure 6- pg. 19
3.2 Figure 7- pg. 21
3.3 Figure 8- pg. 22
3.4 Figure 9- pg. 23
3.5 Figure 10- pg. 24
3.6 Figure 11- pg. 25
3.7 Figure 12- pg. 26
3.8 Figure 13- pg. 27
3.9 Figure 14- pg. 28

4. Discussion- pg. 29

5. Appendices- p. 36

6. References- p. 40

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