University of Guelph

About: University of Guelph is a education organization based out in Guelph, Ontario, Canada. It is known for research contribution in the topics: Population & Poison control. The organization has 26542 authors who have published 50553 publications receiving 1715255 citations. The organization is also known as: U of G & Guelph University.

DNA barcodes for 1/1000 of the animal kingdom

Abstract: This study reports DNA barcodes for more than 1300 Lepidoptera species from the eastern half of North America, establishing that 99.3 per cent of these species possess diagnostic barcode sequences. Intraspecific divergences averaged just 0.43 per cent among this assemblage, but most values were lower. The mean was elevated by deep barcode divergences (greater than 2%) in 5.1 per cent of the species, often involving the sympatric occurrence of two barcode clusters. A few of these cases have been analysed in detail, revealing species overlooked by the current taxonomic system. This study also provided a large-scale test of the extent of regional divergence in barcode sequences, indicating that geographical differentiation in the Lepidoptera of eastern North America is small, even when comparisons involve populations as much as 2800 km apart. The present results affirm that a highly effective system for the identification of Lepidoptera in this region can be built with few records per species because of the limited intra-specific variation. As most terrestrial and marine taxa are likely to possess a similar pattern of population structure, an effective DNA-based identification system can be developed with modest effort.

Local trophodynamics and the interaction of marine mammals and fisheries in the Benguela ecosystem

Abstract: 1. A method for finding the consequences of long-term generalized press perturbations in multispecies ecological communities, with relatively modest requirements for data, is explicated. The approach uses energetic and allometric reasoning to set some parameter values for which data are not available. The remaining unknown parameters are treated as random variables, enabling the calculation of probability distributions for the outcomes that are of interest. 2. The method is used to investigate the effect of a cull of fur seals on fisheries in the Benguela ecosystem, using a 29-species foodweb for that system. In the case of Cape fur seals treated here, it is found that a cull of seals is more likely to be detrimental to total yields from all exploited species than it is to be beneficial. 3. The influence of weak links on the effects of a cull is investigated. Using both consumption by each species and consumption of each species to define link strength, a clear threshold in link strength is found, indicating that 44% of all links could be deleted from the foodweb without affecting the predictions significantly. Even using a criterion based on consumption by each species alone (conventional dietary proportion data), about the same number of links can be deleted without seriously affecting the predictions of the model. This is a very helpful (and encouraging) result for the design of an observational protocol for systematic efforts to gather data for multispecies modelling.

Growing local food: scale and local food systems governance

Abstract: “Scaling-up” is the next hurdle facing the local food movement. In order to effect broader systemic impacts, local food systems (LFS) will have to grow, and engage either more or larger consumers and producers. Encouraging the involvement of mid-sized farms looks to be an elegant solution, by broadening the accessibility of local food while providing alternative revenue streams for troubled family farms. Logistical, structural and regulatory barriers to increased scale in LFS are well known. Less is understood about the way in which scale developments affect the perception and legitimacy of LFS. This value-added opportunity begs the question: Is the value that adheres to local food scalable? Many familiar with local food discourse might suggest that important pieces of added value within LFS are generated by the reconnection of producer and consumer, the direct exchange through which this occurs, and the shared goals and values that provide the basis for reconnection. However, these assertions are based on tenuous assumptions about how interactions within the direct exchange produce value, and how LFS are governed. Examination shows that existing assumptions do not properly acknowledge the hybridity, diversity, and flexibility inherent in LFS. A clear analysis of the potential of scale in LFS will depend on understanding both how value is determined within LFS, and the processes through which these systems are governed. Such an analysis shows that, while scaled-up LFS will be challenged to maintain legitimacy and an identity as “alternative”, the establishment of an open governance process—based on a “negotiation of accommodations”—is likely to enhance their viability.

Diversity loss with persistent human disturbance increases vulnerability to ecosystem collapse

Abstract: Long-term and persistent human disturbances have simultaneously altered the stability and diversity of ecological systems, with disturbances directly reducing functional attributes such as invasion resistance, while eliminating the buffering effects of high species diversity. Theory predicts that this combination of environmental change and diversity loss increases the risk of abrupt and potentially irreversible ecosystem collapse, but long-term empirical evidence from natural systems is lacking. Here we demonstrate this relationship in a degraded but species-rich pyrogenic grassland in which the combined effects of fire suppression, invasion and trophic collapse have created a species-poor grassland that is highly productive, resilient to yearly climatic fluctuations, and resistant to invasion, but vulnerable to rapid collapse after the re-introduction of fire. We initially show how human disturbance has created a negative relationship between diversity and function, contrary to theoretical predictions. Fire prevention since the mid-nineteenth century is associated with the loss of plant species but it has stabilized high-yield annual production and invasion resistance, comparable to a managed high-yield low-diversity agricultural system. In managing for fire suppression, however, a hidden vulnerability to sudden environmental change emerges that is explained by the elimination of the buffering effects of high species diversity. With the re-introduction of fire, grasslands only persist in areas with remnant concentrations of native species, in which a range of rare and mostly functionally redundant plants proliferate after burning and prevent extensive invasion including a rapid conversion towards woodland. This research shows how biodiversity can be crucial for ecosystem stability despite appearing functionally insignificant beforehand, a relationship probably applicable to many ecosystems given the globally prevalent combination of intensive long-term land management and species loss.