Showing papers by "Julian D. Olden published in 2005"

Modelling of stream fishes in the Great Plains, USA

Abstract: Predicting species distributions has important implications for the conservation and management of freshwater fishes, particularly in areas such as the Great Plains, USA where human impacts have resulted in extirpations and declines for numerous native species. There are a number of statistical approaches for constructing distributional models; the accuracy of each is likely dependent on the nature of the environmental gradients, species responses to those gradients and the spatial extent of the modelling. Thus, it is important to compare multiple approaches across species and habitats to identify the most effective modelling approach. Using geographical information system (GIS) derived characteristics of stream segments as predictors, we tested the model performance of three methodologies - linear discriminant function analysis, classification trees and artificial neural networks (ANN) - for predicting the occurrence of 38 fish species in a Great Plains river basin. Results showed that all approaches predicted species occurrences with relatively high success. ANN generally were the best models, in that they generated the most significant models (35 of 38 species) and most accurately predicted species presence for the greatest number of species (average correct classification ¼ 81.1%). The importance of GIS variables for predicting stream fish occurrences varied among species and modelling techniques, but were generally strong predictors of species distributions, including the federally endangered Topeka shiner Notropis topeka. In summary, predictive models should be viewed as both competitive and complementary methodologies for establishing quantitative linkages between fish species and their environment. Our study demonstrates the potential utility of such an approach for guiding conservation efforts for stream fishes of the Great Plains, USA.

The Human Dimensions of Biotic Homogenization

Abstract: Considerable reshuffling of biotas has occurred in recent decades, largely through the gradual replacement of once spatially distinct, native communities with locally expanding and cosmopolitan, non-native ones, in a process coined biotic homogenization (McKinney & Lockwood 1999; Rahel 2000; Olden & Poff 2003; Rooney et al. 2004). Implications of biotic homogenization surfaced recently within the context of discussions about the ecological and evolutionary consequences for animal life (Olden et al. 2004); the manner in which social aspects of human life may also be affected, however, is an issue that has yet to be contemplated. Here, we argue that the social repercussions resonating in the wake of biotic homogenization must not be ignored and consider the idea that the increasingly global uniformity in biological life may be linked to the loss of traditional values and quality of life and have considerable consequences for conservation-oriented advocacy and ecotourism. We draw strong parallels and linkages between biotic homogenization and a more-acknowledged process of cultural homogenization from the social sciences and discuss how this relationship offers a useful analogy for conveying to the public and policy makers the social implications of biotic homogenization. From a purely ethical perspective, one could argue that biotic homogenization will degrade the quality of human life by imbuing biological communities with an aesthetically unappealing uniformity. Biological diversity, and its endemic features, contribute to a person’s attachment to a particular place, become part of a person’s identity, and therefore support an individual’s psychological wellbeing and a community’s identity and image of itself (Horwitz et al. 2001). This so-called sense of place, which links issues of individual and community identity, or who we are, to issues of place, or where we are, is directly threatened by biotic homogenization as endemic elements of the landscape that typify geographic regions and cultures

Allometric growth and sperm competition in fishes

Abstract: The allometric relationship between body mass and gonad mass in males of 23 fish species from 11 families was examined. There was no evidence of a single allometry for all fishes. A cross species analysis suggested a scaling coefficient of 1.04, which was significantly different from a previous study that reported a scaling coefficient of 0.904. A within species analysis generated scaling coefficients from 0.68 to 3.90. Furthermore, for those species characterized by alternative mating tactics. there was no correlation between the scaling coefficients of bourgeois-type males and parasitic-type males. These results are discussed in the context of the gonado-somatic index and its use in testing sperm competition theory.