Project Title:

Investigator(s):

06/2000 - 08/2000

Project Cancelled.  Project file closed, edits are complete.

Scholar-Educator/G.A.A.N.N. funds to D. Yee (internal IUS grant and Department of Education).

Although no consensus has been reached, it is evident that the spatial scale of investigation can have significant effects on productivity-diversity relationships (5, 6, 7). Microcosms, both natural or artificial, are single bounded representations of larger or more complex systems. Microcosms have been used to bridge the gap between theory and nature (8) and the history of their use in testing ecological theory is long (9, 10, 11). Microcosms may lead to mechanistic insights into the structure of natural communities (12, 8), and may provide a way to reduce extraneous variability in seeking answers to questions of general interest. Tree holes are a commonly used natural microcosms for the investigation of community and population level questions in ecology (e.g., 13, 14, 15). Tree holes are found in virtually all forests, and thus they have a wide distribution throughout temperate and tropical regions. Recently, the relationship of productivity and diversity was examined in tree holes in England (15). The authors of this work found an increase in diversity with increasing productivity but their work failed in several crucial ways to assess adequately their hypotheses. First, although productivity was the ecosystem process of interest, initial nutrient conditions were used as a surrogate for productivity. Second, a rather narrow gradient of initial conditions was used and this fact may help to explain why only an increase in diversity with increasing nutrients was found. If a longer gradient of concentration of nutrients were used, the unimodal pattern may appear. In fact, although regional patterns of productivity and diversity appear to be unimodal, monotonic patterns may potentially result at larger scales of observation (16). Third, because tree holes in England are considered depauperate in species, the productivity-diversity relationship may be hard to elucidate and mechanisms that explain it may be harder to address. Tropical systems contain a higher diversity of organisms and also contain more trophic levels. These characteristics may better allow tropical systems to be used to examine the mechanisms underlying the productivity-diversity relationship, especially for those hypotheses concerned with the total species found in a location and hypotheses based on the geological age of habitats (2). Finally, scale was not considered in their investigation. Scale, as mentioned, may affect the pattern that is observed. Thus, a more through examination of the productivity diversity relationship is needed in order to determine if patterns are consistent with theory and to fully test mechanisms hypothesized to cause them. In order to examine the effect of productivity on species diversity across multiple spatial scale, it will be necessary to collect data from as many locations as possible.

Four levels of spatial scale (i.e., cluster, location, region, and geographic area) will be used to assess questions of productivity on patterns of diversity of macroinvertebrates in tree holes. Two geographic areas of interest are temperate (north of the Tropic of Cancer and south of the Tropic of Capricorn) and tropical (all remaining area). Geographic area will be further subdivided into 2 regions each, north and south. Locations will subdivide regions into multiple sites (? 2 per location). Finally, each location will contain a number of clusters (? 3), representing an aggregation of tree holes which are bounded by artificial barriers (e.g., agricultural lands) and exist within the same forest type. Objectives I believe that tree holes should display the same unimodal productivity-diversity relationship common for other systems. This relationship should change depending on the scale of observation. For instance, at small scales we may expect a tight relationship between diversity and productivity. As scale increases towards the regional level, the relationship may become more variable as other factors such as environmental variation impact the relationship. At larger spatial scales, the pattern may change to a linear relationship. A critical objective in all research is first to quantify patterns before investigating processes hypothesized to structure them. With this in mind, the collection of baseline data is essential to allow for the development of testable hypotheses. I plan to collect baseline data during the summer of 2000 from as many potential sites as possible before designing experiments to address hypotheses for subsequent years. My overall goals are to visit potential collecting locations and for each site to determine it?s accessibility, the abundance and diversity of useable tree holes, and to gather preliminary data on taxonomic and functional diversity of macroinvertebrates at each site.

Missing Data Codes:  None

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