Date of Graduation

5-2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor

Steven L. Stephenson

Committee Member

Frederick W. Spiegel

Second Committee Member

Gary R. Huxel

Third Committee Member

Cynthia L. Sagers

Fourth Committee Member

Stephen K. Boss

Fifth Committee Member

Jeffrey Silberman

Keywords

Biological sciences; Amebozoa; Community ecology; Costa Rica; Microbial ecology; Mycetozoa; Myxomycetes

Abstract

Myxomycetes are a group of amoeboid organisms with the capacity of forming fruiting bodies that resemble some macrofungi. The ecology and global distribution of species within the group have been studied only during the last half century. For this reason, a number of questions regarding the nature of the interactions that exist between myxomycetes and their environment still lack the empirical evidence required to obtain complete answers. In the Neotropical region, species assemblages have been moderately well studied, but their biogeography and macroecology have received little attention. In high-elevation areas of this region, the situation is especially precarious, due the lack of formal studies that have considered these potentially threatened ecosystems. In order to fill in some of the information gaps for which previous studies had not provided conclusive evidence, a number of projects outlined in this dissertation were carried out.

The main objective of the research described herein was to study the biogeography and ecology of the myxomycete assemblages associated with high-elevation areas of the northern Neotropics. However, an appreciable effort was directed towards other ecosystems in order to obtain comparative data that could be used to assess other specific questions formulated during the course of the research. With the data generated in this investigation, a number of patterns could be detected at different ecological levels. Among these were that myxomycetes respond to differences in macro- and microenvironmental characteristics of the ecosystems in which they occur. In the first case, myxomycetes seem to respond more or less collectively to some of the parameters that could be measured or determined. However, at the microhabitat level, the selective responses seem to be specific for particular species. This general pattern appears to be consistent and independent of the geographical and historical characteristics of the area. However, the latter seem to have a strong effect on the composition of the assemblage of species present in a particular area.

These observations support the idea that myxomycetes are not neutrally distributed across biomes and ecosystems on earth. In fact, structural differences in the assemblages studied along a latitudinal gradient from the United States to Costa Rica suggest that some myxomycetes have regional distributions. As specific results of this study, the first comprehensive ecological analysis of myxomycetes for a tropical country, a series of updated species diversity lists for three Neotropical countries and a comparison of myxomycete assemblages across three different biogeographical provinces were carried out. It is envisioned that the data generated during this investigation will be used in future studies relating to both myxomycetes and the ecosystems studied. In any case, the data presented herein represent valuable contribution to what is known about the threatened high-elevation forests in the Neotropics.

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