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Variation in Tropical Tree Seedling Survival, Growth, and Colonization by Arbuscular Mycorrhizal Fungi near Conspecific Adults: Field and Shadehouse Experiments in Panama

Eck, Jenalle L
http://rave.ohiolink.edu/etdc/view?acc_num=osu1503242529467534

Abstract Details

2017, Doctor of Philosophy, Ohio State University, Evolution, Ecology and Organismal Biology.
The Janzen-Connell hypothesis highlights the important role of species-specific natural enemies like pathogens and herbivores in maintaining species diversity within plant communities by limiting the survival and growth of seedlings near conspecific adult plants. The extent to which natural enemies reduce conspecific seedling performance is thought to influence species richness and relative abundance within plant communities, but within-species variation in this process could also affect plant diversity at the species or population level. Variation in the strength of natural enemy effects among conspecific seedlings could occur due to factors such as the degree of relatedness between conspecific seedlings and adults (i.e., their level of shared susceptibility), or due to the characteristics of the adult that determine natural enemy accumulation (e.g., reproduction), but the causes of such variation and its consequences for patterns of plant diversity have seldom been explored. I conducted experiments with tropical tree species on Barro Colorado Island, Panama, to test new hypotheses about the causes of variation in survival and growth of conspecific seedlings near adult plants, and to examine how this variation could structure patterns of plant diversity. In Chapter 1, I conducted a shadehouse experiment with the tropical tree species Virola surinamensis to test the hypothesis that highly specialized soil microbial communities accumulate around adults within species and reduce the performance of offspring seedlings relative to non-offspring conspecifics. In Chapter 2, I conducted a field experiment with four tropical tree species to test the hypothesis that seedling performance is reduced beneath the canopies of their own parent trees than beneath those of different conspecific adults. In Chapter 3, I conducted shadehouse and field experiments with V. surinamensis to test the hypothesis that seed production reduces the performance of conspecific seedlings near female trees relative to males by increasing the density of natural enemies beneath females. I found evidence that the soil microbial communities beneath female trees of V. surinamensis reduce the growth and colonization by mutualistic arbuscular mycorrhizal fungi (AMF) of their own offspring seedlings relative to non-offspring conspecifics. This suggests that the genetic relationship between conspecific seedlings and adults determines the outcome of seedling interactions with soil microbes. I did not find evidence that this relationship determined the survival or growth of seedlings of four species beneath conspecific adults in the field. Thus, while highly specialized interactions between soil microbes and tropical trees can occur, when seedlings are exposed to all potential natural enemies and variable environmental conditions, such effects may not be the most important determinants of seedling survival or growth. Lastly, I did not find evidence that seed production by female trees reduces conspecific seedling survival, growth, or colonization by AMF near females relative to males, suggesting that seed production does not alter natural enemy densities or interactions with seedlings in a meaningful way. These findings improve our understanding of the Janzen-Connell hypothesis by providing evidence that interactions between tropical trees and soil microbes can be highly specialized and could help to maintain genetic diversity within tropical tree populations.
Allison Snow (Advisor)
Liza Comita (Advisor)
P. Enrico Bonello (Committee Member)
Simon Queenborough (Committee Member)
163 p.
Ecology
Janzen-Connell hypothesis; plant-soil feedback; tropical trees, seedling recruitment; soil microbes

Recommended Citations

Citations

  • Eck, J. L. (2017). Variation in Tropical Tree Seedling Survival, Growth, and Colonization by Arbuscular Mycorrhizal Fungi near Conspecific Adults: Field and Shadehouse Experiments in Panama [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503242529467534

    APA Style (7th edition)

  • Eck, Jenalle. Variation in Tropical Tree Seedling Survival, Growth, and Colonization by Arbuscular Mycorrhizal Fungi near Conspecific Adults: Field and Shadehouse Experiments in Panama. 2017. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1503242529467534.

    MLA Style (8th edition)

  • Eck, Jenalle. "Variation in Tropical Tree Seedling Survival, Growth, and Colonization by Arbuscular Mycorrhizal Fungi near Conspecific Adults: Field and Shadehouse Experiments in Panama." Doctoral dissertation, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503242529467534

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.