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My dissertation research attempts to identify mechanisms that may underlie patterns of species
diversity. More than twenty five hypotheses have been proposed to explain patterns in regional
or latitudinal gradients of species diversity. However, some mechanisms which may underlie
large-scale patterns of diversity, such as net primary productivity, have failed to explain patterns
of diversity at smaller spatial scales. I test mechanisms to determine if they can explain patterns
of diversity at smaller spatial scales. For example, I am testing the intermediate disturbance hypothesis (IDH), which states that
measures of diversity should peak in areas that experience intermediate disturbance regimes, using orb-weaving spiders that live in
grasslands. I also am testing whether ploidal level of plants underlies patterns of species diversity of
herbivorous insects. My study system is composed of the perennial herb Solidago altissima, the
aphid species Uroleucon luteolum (Williams) and U. nigrotuberculatum (Olive) (Hemiptera:
Aphididae), the leaf galler Asteromyia carbonifera (Osten Sacken) (Diptera: Cecidomyiidae),
and the leaf miners Microrhopala vittata (F.) (Coleoptera: Chrysomelidae), and Ophiomyza sp. 1
and Phytomyza sp. 1 (Diptera: Agromyzidae; species currently undescribed). This system is
ideal to characterize relationships between ploidal level of host plants and the structure of
arthropod communities. S. altissima is a dominant herb in oldfield habitats throughout North
America and can be diploid, tetraploid, or hexaploid. The herbivores are specialists on S.
altissima, are common, and often are patchily dispersed within and among stands.
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