Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 168-181). Also available on the World Wide Web.

Many species of stream invertebrates gain most of their energy by the consumption of coarse detrital materials. While most of these organisms are univoltine or semivoltine, the biomass of assimilable detritus varies seasonally as a result of several processes. The period of detritus input is highly seasonal, decomposition rates are positively temperature dependent, and winter spates result in fragmentation and flushing of detrital materials. From two years of measuring detritus inputs and standing crops, I showed that the abundance of this resource varied by almost two orders of magnitude seasonally. Since many consumers which rely on this resource have generation times equal to that of the period of resource variation, individuals and perhaps populations may be faced with periods of low food abundance. This work addressed the consequences of seasonal food limitation of stream insects. To test this food Limitation hypothesis, I experimentally manipulated detritus input rates to otherwise natural communities of stream benthos using a replicated, 3 - treatment design. These experiments were conducted in experimental streams in the University of British Columbia research forest over the course of one year. Increasing input rates of detritus resulted in large increases in size at maturity and growth rates for 7 of 9 common species. This was true for both summer and winter emerging species. Increased supply of detritus also resulted in increased densities and higher rates of colonization for some species. There was no evidence of change in phenology for any species. The densities of the chironomid Brillia retifinis (the only species studied that had a short generation time) underwent exponential growth during the first 3 months of the experiment, reaching densities 10x those of the control and natural streams. This species apparently fills the role of a "fugitive" in this system. One alternative hypothesis for increased densities following addition of whole leaf detritus was a significantly altered microhabitat. To test this possibility I compared the use of real and artificial (polyester) leaf packs by stream invertebrates. Those species which typically consume coarse detritus were almost never found on the artificial leaf packs, while they attained high densities on the real leaves. In contrast, fine-particle, and algae consuming species were found in similar densities on artificial and real leaf packs, although there was a time lag in colonization of the polyester leaves. These results suggest that microhabitat alone cannot lead to increased densities of detritivores. The densities of species which do not consume large particles of detritus also were affected by whole-leaf additions. Density of total consumers of fine particles of detritus increased when coarse detritus was supplemented and most taxa showed this response. This result was apparently an indirect effect of diminution of detrital particle size by larger detritivores. Predaceous species also increased in density under detritus supplementation. Increased densities of taxa other than large-particle-detritus feeders indicates that effects at one trophic level can affect other trophic levels. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Community structure in backswimmers (Hemiptera: Notonectide), was investigated via extensive sampling throughout southern Arizona, USA, and Sonora, Mexico, from 1980 through 1985. Co-occurrence and relative abundance data were collected in more than 65 ponds, and in 177 rock basin pools (tinajas) in 21 canyons in the Southwest. Eleven species were collected in Arizona and Sonora, and were divided into two groups, species found in ponds and species found in tinajas. Only two species occurred significantly in both habitats. Tinaja species are largely Southwst endemics, and pond species are widespread or tropical in distribution. Data from artificial habitats suggest that the tinaja species use relatively high topographic relief, and pond species use relatively large surface area as cues to find their respective habitats. Two body size patterns are consistent with a competition explanation of local community structure. The body sizes of co-occurring species are relatively evenly distributed among species occurring in pond and tinaja habitats, and species of similar body size tend not to co-occur (body size ratio <1.3). For example, Notonecta kirbyi and N. lobata only co-occur in tinajas at intermediate elevations; lobata is absent at high elevations and kirbyi is absent at lower elevations. N. indica occurs in ponds at lower elevations and N. unifasciata occurs at higher elevations. Buenoa hungerfordi and B. arizonis both occur in tinajas, but not at the same time of year. Predation was shown experimentally not to be important in producing the body size pattern. Notonecta spp. preyed heavily on the smaller of two Buenoa species presented, an effect that would act to reduce the community-wide body size ratio. Because notonectid communities have larger body size ratios than expected by chance, predation would seem not to be involved in producing this pattern. However, predation does appear to reinforce microhabitat partitioning between the two genera in that Buenoa occupy deeper portions of the water column in the presence of Notonecta than in their absence. This further displaces coexisting individuals of the two genera in space, and reduces overlap in foraging for aquatic insect prey and promotes coexistence.

Thesis (M. Sc.)--Carleton University, 2002. / Includes bibliographical references (p. 21-25). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Washington, 1997. / Includes bibliographical references (leaves [90]-96).

Thesis (Ph. D.)--University of Wisconsin, 1954. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 45-50).

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 152-163).

The Cape Horn Biosphere Reserve, within the remote Sub-Antarctic ecoregion is a reservoir of expressions of biological and cultural diversity. Although it is considered one of 24 wilderness areas remaining in the world, it is not free from local and global threats, such as invasive species, and climate change. Field biologists and philosophers associated to the Sub-Antarctic Biocultural Conservation Program and the Omora Ethnobotanical Park, have worked to describe the region’s biocultural diversity, linking ecological and philosophical research into education, ecotourism, and conservation, through a methodology called field environmental philosophy (FEP), which integrates ecological sciences and environmental ethics through a 4-step cycle consisting of: 1) interdisciplinary research; 2) composition of metaphors; 3) design of field activities with an ecological and ethical orientation; and 4) implementation of in situ conservation areas. In this context, the purposes of this dissertation were to: 1) provide a comprehensive review of publications regarding the conservation status of aquatic and terrestrial insects at a global scale and with an emphasis in southern South America; 2) study the distribution of benthic macroinvertebrates through the sharp altitudinal gradient of the Róbalo River watershed; 3) describe the life histories of Gigantodax sp (Simuliidae: Diptera) and Meridialaris chiloeense (Leptophlebiidae: Ephemeroptera) in the Róbalo River and to assess the potential effects of climate change on their phenology; and 4) to apply FEP methodology in order to better understand and communicate the intrinsic and instrumental values of freshwater invertebrates in the Cape Horn Biosphere Reserve.

No description available.