Bruce D. Maxwell

ELK ALTER HABITAT SELECTION AS AN ANTIPREDATOR RESPONSE TO WOLVES

For elk (Cervus elaphus) in the Gallatin drainage of the Greater Yellowstone Ecosystem, Montana, USA, wolf movements caused local predation risk to vary substan- tially on a time scale of days. Spatially and temporally fine-scaled data from GPS radio collars show that elk moved into the protective cover of wooded areas when wolves were present, reducing their use of preferred grassland foraging habitats that had high predation risk. By constraining habitat selection, wolves may have greater effects on elk dynamics than would be predicted on the basis of direct predation alone. Based on changes in the woody vegetation following the reintroduction of wolves, it has been suggested that an- tipredator responses by elk may be driving a trophic cascade in the Yellowstone ecosystem. However, studies to date have been hampered by a lack of direct data on spatial variation in predation risk, and the ways in which elk respond to variation in risk. Our data support a central portion of the hypothesis that elk antipredator behavior could drive a trophic cascade, but changes in elk numbers are also likely to have affected elk-plant interactions.

Navigating a Critical Juncture for Sustainable Weed Management

Agricultural weed management has become entrenched in a single tactic—herbicide—resistant crops—and needs greater emphasis on integrated practices that are sustainable over the long term. In response to the outbreak of glyphosate-resistant weeds, the seed and agrichemical industries are developing crops that are genetically modified to have combined resistance to glyphosate and synthetic auxin herbicides. This technology will allow these herbicides to be used over vastly expanded areas and will likely create three interrelated challenges for sustainable weed management. First, crops with stacked herbicide resistance are likely to increase the severity of resistant weeds. Second, these crops will facilitate a significant increase in herbicide use, with potential negative consequences for environmental quality. Finally, the short-term fix provided by the new traits will encourage continued neglect of public research and extension in integrated weed management. Here, we discuss the risks to sustainable agriculture from the new resistant crops and present alternatives for research and policy.

ECOLOGICAL SUPPORT FOR RURAL LAND-USE PLANNING

How can ecologists be more effective in supporting ecologically informed rural land-use planning and policy? Improved decision making about rural lands requires careful consideration of how ecological information and analyses can inform specific planning and policy needs. We provide a brief overview of rural land-use planning, including recently developed approaches to conservation. Effective participation in land-use planning requires ecologists to understand trade-offs—for example, the need to balance a land owners desire for a fair and predictable process with the “learn as you go” approach of adaptive management—and the importance of integrating local knowledge with landscape-level information. Four primary challenges require attention from ecologists to improve rural land-use planning. First is the mismatch between the spatial and temporal scales in which ecological processes occur and the scales and tempos of land-use planning. Second, ecologists must engage in interdisciplinary research to critica...

Dicamba resistance in kochia

Abstract Kochia plants resistant (R) to field rates of dicamba were characterized for their frequency of occurrence and levels of resistance and for the physiological fate of applied 14C-dicamba. Of 167 randomly sampled fields and seven fields identified by producers to contain R kochia, 19 contained plants that produced 1% or more R progeny. The maximum percentage of R progeny produced by parental plants from any field was 13%. An inbred R line derived from a field collection was 4.6-fold more resistant to dicamba than an inbred susceptible (S) line. Rates of 14C-dicamba uptake and translocation were similar in R and susceptible (S) plants up to 168 h after treatment (HAT). Concentrations of the primary metabolite, 5-hydroxy dicamba, were similar in R and S tissues up to 60 HAT, although amounts were significantly greater in R treated leaves by 96 and 168 HAT. However, because there were negligible levels of dicamba metabolites in R shoots and because the rate of metabolism was relatively slow, the observed changes were inadequate to account for observed resistance levels. Thus, dicamba resistance in kochia cannot be attributed to differential herbicide absorption, translocation, or metabolism. These findings, together with our field observations on the unusually slow spread of resistance within and among fields may indicate that dicamba resistance is a quantitative trait. Nomenclature: Dicamba; kochia, Kochia scoparia (L.) Schrad KCHSC.

Predicting the occurrence of nonindigenous species using environmental and remotely sensed data

Abstract To manage or control nonindigenous species (NIS), we need to know where they are located in the landscape. However, many natural areas are large, making it unfeasible to inventory the entire area and necessitating surveys to be performed on smaller areas. Provided appropriate survey methods are used, probability of occurrence predictions and maps can be generated for the species and area of interest. The probability maps can then be used to direct further sampling for new populations or patches and to select populations to monitor for the degree of invasiveness and effect of management. NIS occurrence (presence or absence) data were collected during 2001 to 2003 using transects stratified by proximity to rights-of-way in the northern range of Yellowstone National Park. In this study, we evaluate the use of environmental and remotely sensed (LANDSAT Enhanced Thematic Mapper +) data, separately and combined, for developing probability maps of three target NIS occurrence. Canada thistle, dalmation toadflax, and timothy were chosen for this study because of their different dispersal mechanisms and frequencies, 5, 3, and 23%, respectively, in the surveyed area. Data were analyzed using generalized linear regression with logit link, and the best models were selected using Akaikes Information Criterion. Probability of occurrence maps were generated for each target species, and the accuracies of the predictions were assessed with validation data excluded from the model fitting. Frequencies of occurrence of the validation data were calculated and compared with predicted probabilities. Agreement between the observed and predicted probabilities was reasonably accurate and consistent for timothy and dalmation toadflax but less so for Canada thistle. Nomenclature: Canada thistle, Cirsium arvense L. CIRAR; dalmation toadflax, Linaria dalmatica (L.) P. Mill. LINDA; timothy, Phleum pratense L. PHLPR.

Lessons from agriculture may improve the management of invasive plants in wildland systems

The current motivating concept underlying our view of invasive plant species is that they are dangerous and destructive invaders that drive native plant communities to extinction and must be eradicated at almost any cost. This negative view of non-native plants has resulted in the adoption and implementation of control efforts that may not be entirely successful and have the potential to result in severe non-target effects. The history of weed control in agroecosystems may provide insights on how to deal with non-native plant species in non-crop-lands, and shed light on some of the potential consequences of current control programs for the environment and for non-target organisms. Alternative research and management foci, based on knowledge gleaned from agricultural systems, may improve the effectiveness and sustainability of non-native plant species management in range- and wildlands.

A standardized set of metrics to assess and monitor tree invasions

Abstract Scientists, managers, and policy-makers need functional and effective metrics to improve our understanding and management of biological invasions. Such metrics would help to assess progress towards management goals, increase compatibility across administrative borders, and facilitate comparisons between invasions. Here we outline key characteristics of tree invasions (status, abundance, spatial extent, and impact), discuss how each of these characteristics changes with time, and examine potential metrics to describe and monitor them. We recommend quantifying tree invasions using six metrics: (a) current status in the region; (b) potential status; (c) the number of foci requiring management; (d) area of occupancy (AOO) (i.e. compressed canopy area or net infestation); (e) extent of occurrence (EOO) (i.e. range size or gross infestation); and (f) observations of current and potential impact. We discuss how each metric can be parameterised (e.g. we include a practical method for classifying the current stage of invasion for trees following Blackburn’s unified framework for biological invasions); their potential management value (e.g. EOO provides an indication of the area over which management is needed); and how they can be used in concert (e.g. combining AOO and EOO can provide insights into invasion dynamics; and we use potential status and threat together to develop a simple risk analysis tool). Based on these metrics, we propose a standardized template for reporting tree invasions that we hope will facilitate cross-species and inter-regional comparisons. While we feel this represents a valuable step towards standardized reporting, there is an urgent need to develop more consistent metrics for impact and threat, and for many specific purposes additional metrics are still needed (e.g. detectability is required to assess the feasibility of eradication).

Elk decision-making rules are simplified in the presence of wolves

The risk of predation drives many behavioral responses in prey. However, few studies have directly tested whether predation risk alters the way other variables influence prey behavior. Here we use information theory (Akaike’s Information Criterion, AICc) in a novel way to test the hypothesis that the decision-making rules governing elk behavior are simplified by the presence of wolves. With elk habitat use as the dependent variable, we test whether the number of independent variables (i.e., the size of the models) that best predict this behavior differ when wolves are present vs absent. Thus, we use AICc scores simply to determine the number of variables to which elk respond when making decisions. We measured habitat use using 2,288 locations from GPS collars on 14 elk, over two winters (14 elk winters), in the Gallatin Canyon portion of the Greater Yellowstone Ecosystem. We found that the use of three major habitat components (grass, conifer, sage) was sensitive to many variables on days that wolves were locally absent, with the best models (ΔAICc≤2) averaging 7.4 parameters. In contrast, habitat use was sensitive to few variables on days when wolves were present: the best models averaged only 2.5 parameters. Because fewer variables affect elk behavior in the presence of wolves, we conclude that elk use simpler decision-making rules in the presence of wolves. This simplification of decision-making rules implies that predation risk imposes selection pressures that do not allow prey to respond to other pressures in ways that they otherwise would. If the affected processes are important, then this indirect effect of predation is likely to be important.

Plant diversity: new insights from molecular biology and genomics technologies

Abstract Technological advances in molecular biology have contributed substantially to our understanding of plant genetic diversity. Early studies of allozyme variation employing protein electrophoresis revealed that plant populations have high levels of genetic diversity, most of the variation at polymorphic loci is found within populations, and geographic range and breeding system explain the largest proportion of variation in genetic diversity. With the discovery of restriction endonucleases, the first DNA-based markers allowed the detection of variation in DNA sequences in plant population studies. More recently, techniques that utilize the polymerase chain reaction have allowed a more representative assessment of genetic variation in plants by screening multiple loci distributed throughout the genome. The analyses reveal sufficient polymorphism for the examination of fine-scale genetic differences among individuals. Information on plant genetic diversity is also emerging from studies of plant genome structure. Comparative genetic mapping studies of members of the Brassicaceae, Poaceae, and Solanaceae show that gene content is highly conserved between closely related species, although gene order on a chromosomal segment may differ between species. Comparative sequencing studies reveal higher degrees of diversity at the microstructural (less than 1 million base pairs) level than predicted at the genetic map level and suggest that genes are densely packed in gene-rich regions, rather than randomly distributed along chromosomes in species with large genomes. Sequencing of the entire genomes of rice and Arabidopsis thaliana will help identify genes controlling agronomically important traits, improve our understanding of genetic variation for fitness-related traits in wild plant populations including weed species, resolve evolutionary relationships among plant taxa, and potentially revolutionize current ideas on plant diversity and evolution. Nomenclature: Mouse-ear cress, Arabidopsis thaliana (L.) Heynh.; rice Oryza sativa L.

The Rationale for Monitoring Invasive Plant Populations as a Crucial Step for Management

Abstract Many land managers are faced with trying to optimize management of invasive plant species based on budget constraints and lack of knowledge of the true potential of the species. Generally, “early detection rapid response” (EDRR) is the assumed best management strategy and tends to drive management regardless of the invasion stage or possible variation in the invasion potential of the population. We created a simulation model to evaluate the optimal management strategy to reduce the rate of invasion of nonindigenous plant species. The strategies were specifically chosen to assess the value of information from monitoring populations. We compared four management strategies and a no-management control over a 20-yr period in the context of a management area: (1) managing a fixed number of populations at random each year (EDRR random), (2) managing an equivalent number of populations along a road each year (EDRR road), (3) managing half of the fixed populations that were determined by monitoring to be sources of new populations (monitoring every year), and (4) managing an equivalent set of source populations only on even years, leaving the odd years for monitoring (monitoring every other year). EDRR random location without regard to population invasion potential, and monitoring every year targeting management on populations determined to be invasive (sources for new populations), were the most successful strategies for reducing the increase in total number of populations. The model simulations suggest that managers could dedicate 50% of their management time to monitoring without risk of accelerating invasions or reducing the impact of their weed management program.