National City, CA, United States
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Whiteley A.R.,University of Massachusetts Amherst | Hastings K.,Resources Management and Science | Wenburg J.K.,U.S. Fish and Wildlife Service | Frissell C.A.,Pacific Rivers Council | And 2 more authors.
Conservation Genetics | Year: 2010

Following glacial recession in southeast Alaska, waterfalls created by isostatic rebound have isolated numerous replicate populations of coastal cutthroat trout (Oncorhynchus clarkii clarkii) in short coastal streams. These replicate isolated populations offer an unusual opportunity to examine factors associated with the maintenance of genetic diversity. We used eight microsatellites to examine genetic variation within and differentiation among 12 population pairs sampled from above and below these natural migration barriers. Geological evidence indicated that the above-barrier populations have been isolated for 8,000-12,500 years. Genetic differentiation among below-barrier populations (FST = 0.10, 95% C. I. 0.08-0.12) was similar to a previous study of more southern populations of this species. Above-barrier populations were highly differentiated from adjacent below-barrier populations (mean pairwise FST = 0.28; SD 0.18) and multiple lines of evidence were consistent with asymmetric downstream gene flow that varied among streams. Each above-barrier population had reduced within-population genetic variation when compared to the adjacent below-barrier population. Within-population genetic diversity was significantly correlated with the amount of available habitat in above-barrier sites. Increased genetic differentiation of above-barrier populations with lower genetic diversity suggests that genetic drift has been the primary cause of genetic divergence. Long-term estimates of Ne based on loss of heterozygosity over the time since isolation were large (3,170; range 1,077-7,606) and established an upper limit for Ne if drift were the only evolutionary process responsible for loss of genetic diversity. However, it is likely that a combination of mutation, selection, and gene flow have also contributed to the genetic diversity of above-barrier populations. Contemporary above-barrier Ne estimates were much smaller than long-term Ne estimates, not correlated with within-population genetic diversity, and not consistent with the amount of genetic variation retained, given the approximate 10,000-year period of isolation. The populations isolated by waterfalls in this study that occur in larger stream networks have retained substantial genetic variation, which suggests that the amount of habitat in headwater streams is an important consideration for maintaining the evolutionary potential of isolated populations. © 2010 Springer Science+Business Media B.V.

Walden-Schreiner C.,North Carolina State University | Leung Y.-F.,North Carolina State University | Newburger T.,Resources Management and Science | Woiderski B.,Resources Management and Science
Park Science | Year: 2012

Open landscapes are common, valued park resources that serve as vital wildlife and plant habitats as well as sites for diverse visitor activities. Although the National Park Service (NPS) actively manages these resources, open landscapes are subject to a variety of ecological pressures exacerbated by anthropogenic threats, including intense visitor use that is often not well documented despite its managerial relevance. Established and valuable counting methods exist to estimate visitor use at static locations, yet open landscapes present special monitoring challenges because of multiple points of visitor access and limited or no containment infrastructure. In this article we present an accessible, replicable, and acceptably accurate method developed for monitoring visitor use and its spatial distribution in open landscapes. This method was implemented in three high-use meadows of Yosemite National Park in the summer of 2011. We highlight the data utility and analytical options, evaluate the benefits and limitations, and discuss the potential for volunteer involvement to sustain longitudinal data collection. Additionally, we provide suggestions of other open landscapes suitable for implementation of this method, such as coastal and urban-proximate units of the National Park System.

Newburger T.,Resources Management and Science | Jones M.,Resources Management and Science | Kuhn B.,Resources Management and Science | Woiderski B.,Resources Management and Science
Environmental Management | Year: 2011

Informal trails created or perpetuated by visitors is a management challenge in many protected natural areas such as Yosemite National Park. This is a significant issue as informal trail networks penetrate and proliferate into protected landscapes and habitats, threatening ecological integrity, aesthetics, and visitor experiences. In order to develop effective strategies for addressing this problem under an adaptive management framework, indicators must be developed and monitoring protocol must be established to gather timely and relevant data about the condition, extent, and distribution of these undesired trail segments. This article illustrates a process of developing and evaluating informal trail indicators for meadows in Yosemite Valley. Indicator measures developed in past research were reviewed to identify their appropriateness for the current application. Information gaps in existing indicator measures were addressed by creating two new indices to quantify the degree of informal trailing based on its land fragmentation effects. The selected indicator measures were applied to monitoring data collected between 2006 and 2008. The selected measures and indices were evaluated for their ability to characterize informal trail impacts at site and landscape scales. Results demonstrate the utility of indicator measures in capturing different characteristics of the informal trail problem, though several metrics are strongly related to each other. The two fragmentation indices were able to depict fragmentation without being too sensitive to changes in one constituent parameter. This study points to the need for a multiparameter approach to informal trail monitoring and integration with other monitoring data. Implications for monitoring programs and research are discussed. © 2010 Springer Science+Business Media, LLC.

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