Species diversity is influenced by disturbance in the environment. Ground beetles (Coleoptera: Carabidae) were used as a model taxon to study the effects of disturbance (i.e., time since disturbance) in different habitats along a successional gradient (agricultural fields, old fields, young forests and old forests). Seventy-three species (5139 individuals) were collected during both years of sampling, of which 9 species are introduced species and compose 64.8% of the total catch. In contrast to the predictions of the Intermediate Disturbance Hypothesis, diversity of ground beetles was higher in the agricultural fields and lowest in the old forests. The community composition, as seen with Nonmetric Multidimensional Scaling ordination, in the agricultural fields was the most distinct, while the difference between and among other habitats was less clear, possibly influenced by the introduced species present in the area. The introduced species collected had a significant influence in the total catch as they represented more than half of the total individuals collected and in the ground beetle community composition. The distribution of seven introduced species in Quebec was studied and compared to what was reported in 1975. Five species have a similar distribution, while the distribution range of Harpalus rufipes DeGeer has expanded south and Bembidion obtusum Audinet-Serville might have been dispersing northeast since its introduction.

No description available.

The nutria (Myocastor coypus) is a semi-aquatic rodent native to South America that was introduced to the Pacific Northwest, USA, in the 1930s. Primary damage categories from this invasive species include burrowing and herbivory, resulting in habitat degradation. Nutria have become well-established in metropolitan habitats, and anecdotal information suggests the problem has increased in recent years. However, little regional research on the species has been conducted. The scope of this research, which emphasizes metropolitan habitats, includes three primary foci in relation to nutria populations in the Pacific Northwest: modeling habitat suitability, assessing activity and movement patterns, and identifying and managing negative impacts. Large-scale management of any invasive species requires understanding of the current and potential future population distribution. Cold temperatures have been assumed to be a limiting factor for the geographic distribution of nutria populations, but this assumption had not been explicitly tested. A mechanistic habitat suitability model based on winter temperatures performed well in predicting nutria distribution in the Pacific Northwest and nationally. Regional results suggest nutria currently occupy most accessible suitable habitat. However, coupling the model with future climate change data suggests a much larger suitable habitat zone regionally and nationally in the near future. Management of an invasive species on a local scale requires region-specific information about behavior patterns. Radio-telemetry tracking of local nutria populations in metropolitan habitats suggested higher diurnal activity levels than reported elsewhere. Activity areas were also on the lower end of reported nutria home ranges, suggesting the studied metropolitan wetland sites represent core habitat for nutria in the region. Comparison of two transmitter attachment methods, a neck collar and a tail mount, did not identify a clearly superior attachment method for short-term nutria behavior studies. The presence of nutria in metropolitan habitats in the Pacific Northwest necessitates the need to expand the limited management techniques available for these habitats. Standard Vexar® plastic mesh tubes very effectively mitigated nutria herbivory damage to woody vegetation live stakes planted in a metropolitan habitat restoration site. A recently developed nutria multiple-capture cage trap captured larger nutria and reduced non-target captures compared to a standard cage trap. The design of the multiple-capture trap, however, prevented multiple-capture events because small nutria escaped the trap. This research contributes substantially to previously limited information about nutria in the Pacific Northwest and resulted in several new findings. Climate change modeling provides the first evidence that nutria ranges could expand in the near future. Evaluation of new radio-telemetry methods will benefit future behavior studies. The assessment of new damage prevention tools provides more options for the management of nutria in urban habitats. Management recommendations include creating regional nutria management plans, identifying and targeting priority monitoring regions, finding key stakeholders, focusing on public education, and initiating a pilot control program. Recommendations for research include evaluating effects on native fauna, conducting disease surveys, assessing the extent of damage, continuing habitat suitability analysis, and developing population indices.

Aquatic invasive species are a major threat to native freshwater biodiversity. The North American signal crayfish Pacifastacus leniusculus was introduced to Great Britain during the 1970s and is now widely distributed throughout England, Wales and Scotland. First recorded in Scotland in 1995, P. leniusculus is now established at more than twenty sites. The only other introduced crayfish species present in Scotland is the white-clawed crayfish Austropotamobius pallipes. A. pallipes is restricted to only two locations in Scotland, Loch Croispol and Whitemoss Reservoir. P. leniusculus negatively impacts macrophytes, invertebrates and fish though ecological and physical processes. Additionally, P. leniusculus has displaced A. pallipes throughout much of its native range within Great Britain due to competition and disease. Consequently, the two A. pallipes populations in Scotland have a high conservation value. This PhD study aimed to improve understanding of P. leniusculus invasion success by examining trophic dynamics and to develop methodologies that could improve the detection and control of P. leniusculus populations in Scotland. Stable isotope analysis was used to determine the diet composition, trophic position and whether an ontogenetic dietary shift occurs in the Loch Ken population of P. leniusculus. Bayesian mixing models indicated that P. leniusculus in Loch Ken do exhibit an ontogenetic dietary shift. Additionally, individuals of all sizes occupied the trophic position of a predator in Loch Ken suggesting that invertebrates and fish constitute an important component of P. leniusculus diet. Stable isotope analysis was used once again to compare the isotopic niche width and diet composition of P. leniusculus populations from Loch Ken and A. pallipes populations from Loch Croispol and Whitemoss Reservoir. At the species level, A. pallipes exhibited a larger niche width than that of P. leniusculus. At the population level, the isotopic signatures of the A. pallipes populations were considerably different from each other suggesting an overestimation of A. pallipes’ niche width at species level. Results showed no dietary overlap between species and Bayesian mixing models suggested P. leniusculus and A. pallipes were consuming different resources, indicating there would be no direct competition for food resources if they were to co-occur. A plus-maze study was used to determine if P. leniusculus exhibited a preference for one of four food attractants (Oncorhynchus mykiss, P. leniusculus, beef or vegetation), which could be used to improve trapping efficiency. In the maze system, P. leniusculus exhibited no preference for any food attractant presented. This would suggest that either the maze was not a good model or food attractants would not improve trapping efficiency of P. leniusculus. Additionally, a comparative investigation into the use of gill nets as a method to control P. leniusculus was conducted. Results showed that the net type and the presence of fish entangled in the net influenced the number of P. leniusculus caught. Finally, environmental DNA (eDNA) was used and evaluated for detection of P. leniusculus. A robust quantitative Polymerase Chain Reaction (qPCR) assay and DNA extraction protocol were developed. Using the developed qPCR assay, P. leniusculus eDNA was detected in controlled aquaria conditions but not in environmental water samples collected from the field. Furthermore, the quantities of P. leniusculus eDNA declined in aquaria conditions while individuals were still present suggesting the mechanisms for eDNA release by P. leniusculus are complex. Stable isotope analysis indicates that P. leniusculus exhibit an ontogenetic dietary shift, and in each life stage, P. leniusculus function as an omnivore but occupy the trophic position of a predator. Niche width analysis revealed that the diet of P. leniusculus was less general than that observed in A. pallipes and thus diet of P. leniusculus may not be responsible for invasive success. Food attractants will not enhance trapping efficiency but nets may present a potential new method to control P. leniusculus. Similarly, eDNA presents a promising new method for rapid detection of P. leniusculus. It will not be possible to eradicate P. leniusculus in Scotland but the findings of this PhD may help prevent establishment of new populations. These results should be incorporated into future management strategies for P. leniusculus populations in Scotland and may have broader applications in Great Britain and Europe.

"August 2003." / Includes bibliographical references (leaves 294-333) / 2 v. (xxxi, 333 leaves) ; ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Plant and Pest Science, 2005