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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Natural enemies in a variable world

Stump, Simon 16 September 2015 (has links)
<p>Natural enemies are ubiquitous in nature. In many communities, natural enemies have a major effect on the diversity of their prey. Their effects are very diverse: they can promote or undermine the ability of their prey to coexist through a variety of mechanisms. As such, an important step in understanding how diversity is maintained will be to understand how different forms of predator behavior affect prey coexistence. In this dissertation, I study how two major types of predators affect plant coexistence in two different communities. </p><p> First, I study natural enemies in tropical forests, using both theory and empirical work. In tropical forests, most natural enemies are thought have a narrow host range, and be distance-responsive (i.e., mainly harm seeds and seedlings that are near adults of their main host). Previous theoretical work has shown that specialized natural enemies can maintain diversity of their prey, whether or not they are distance-responsive. However, it is unknown whether specialist natural enemies are more or less able to promote prey coexistence if they are distance-responsive. Using theoretical models, I show that distance-responsive predators are less able to maintain diversity. Additionally, I show that habitat partitioning does not interfere with the ability of distance-responsive predators to maintain diversity, even if it causes seedling survival to be highest near conspecific adults. </p><p> From an empirical aspect, I studied the host range of seed-associated fungi. Soil-borne microbes, such as fungi, are thought to play an important role in maintaining diversity in tropical forests. However, the microbial community itself is often treated as a black box, and little is known about which microbes are causing major effects, or how specialized seed-microbe associations are. Here I use experimental inoculations to examine the host range and effect of a guild of seed-associated fungi that are thought to be mainly pathogens. I show that fungal species are differentially able to colonize different seed species, and have species-specific effects on seed germination. I show that in many cases, plant phylogeny, and to a lesser extent fungus phylogeny, are good predictors of colonization. </p><p> Finally, I study how an optimally foraging granivore can promote (or undermine) coexistence amongst annual plants, using theory. Optimal foraging theory is one of the major theories for how predators behave; despite this, little is known about whether an optimally foraging predator could promote coexistence amongst a diverse community of prey. Previous models have shown than two species can coexist due to optimal foraging, but did not test whether multiple prey can coexist, nor if the effect is altered by environmental variation. Here, I show that if the predators specialize on different prey at different times, the predators can allow multiple prey species to coexist. In this case, environmental variation has little effect on the ability of predators to maintain diversity. If the predators are generalists, they cannot maintain diversity. Additionally, I show that generalist predators will create a negative storage effect, undermining coexistence. </p>

The comparative ecology of two water snakes, Natrix rhombifera and Natrix erythrogaster in Oklahoma /

Preston, William Burton, January 1970 (has links)
Thesis (Ph. D.)--University of Oklahoma, 1970. / Includes bibliographical references (leaves 75-79).

Embodiment and embeddedness in philosophies of ecology deep ecology, Confucian ecology, and Maurice Merleau-Ponty's phenomenology /

Schlottmann, Chris. January 2002 (has links)
Thesis (B.A.)--Haverford College, Dept. of Philosophy, 2002. / Includes bibliographical references.

Analysis of ecological data /

Ngai, Wai-ting, Eric. January 1900 (has links)
Thesis (M. Soc. Sc.)--University of Hong Kong, 1991.

Analysis of ecological data

Ngai, Wai-ting, Eric. January 1900 (has links)
Thesis (M.Soc.Sc.)--University of Hong Kong, 1991. / Also available in print.

The relative effectiveness of three levels of abstraction representing the conceptual scheme of equilibrium as an advance organizer in teaching ecological systems by televised instruction /

Triezenberg, Henry J. January 1967 (has links)
Thesis--University of Wisconsin. / Description based on print version record. Includes bibliographical references (leaves 95-99).

Fifth and eighth grade students' orientations toward the environment and environmental problems

Horvat, Robert Emil, January 1974 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1974. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Development of environmental education a mechanism for integrating high school and university environmental programs /

Westphal, Joanne Dobron. January 1973 (has links)
Thesis (M.S.)--University of Wisconsin--Madison. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 24-25).

Structuring learning experiences in the community an integral part of environmental education.

Lambert, Geraldine Kay, January 1974 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1974. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Plant-microbe associations controls on soil bacterial community structure and consequences for aboveground plant communities /

Swedo, Barbara L. January 2008 (has links)
Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2008. / Title from PDF t.p. (viewed on Jul 28, 2009). Source: Dissertation Abstracts International, Volume: 69-12, Section: B, page: 7260. Adviser: Heather L. Reynolds.

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