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Pines are highly invasive trees that are commonly used in pine plantations throughout the Southern Hemisphere. However, the survival and subsequent invasion of pines in exotic environments are dependent on the obligate symbiosis between ectomycorrhizal (ECM) fungi and pines. ECM fungi vary in host specificity and compatibility from pine-specialist species in the genus Suillus to broad generalists, such as species within the genera Pisolithus and Scleroderma. In Experiment 1, we sought to understand how the geographic origin of ECM fungi native to the southeastern United States and two pine species (native southeastern United States Pinus taeda and exotic Pinus radiata, which is commonly used in pine plantations) affects ECM colonization of the host plant in a growth chamber experiment where host plants were inoculated with meiotic ECM fungal spores. Selection among these genetically diverse ECM fungal spores during host plant colonization potentially provided an opportunity for rapid evolution of host specificity to occur. In Experiment 2, we tested whether the ECM fungi underwent rapid evolution by planting a neighbor seedling of the same or different pine species next to the established, colonized seedling from Experiment 1 and comparing how the ECM fungi responded. We found no evidence that rapid evolution of host specificity occurred; instead, our results indicate that native ECM fungi are more compatible with the native host P. taeda. However, the exotic host P. radiata grows faster in response to colonization by native Suillus, which could explain the association between Suillus and P. radiata in successful pine invasions.
Long, Hailey A., "Compatibility Between Native Mississippi Ectomycorrhizal Fungi and Native and Exotic Pine Hosts: Testing for Specificity and the Potential for Rapid Evolution" (2023). Honors Theses. 2972.
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