|Friday, April 15th|
9:00 AM - 9:20 AM
We undertook this study to test a current hypothesis that, during locomotion, proximal, parallel-fibered muscles maximize work whereas distal, pennate muscles maximize isometric force. Using pigeons (N = 2) in different modes of flight (ascending, level, descending), we test two muscles for comparison against the pectoralis (PECT). The PECT is a large, proximally-located parallel-fibered muscle, known from previous work to be the primary source of work and power during downstroke. The scapulohumeralis caudalis (SHC) is a parallel-fibered muscle, proximal muscle that retracts and elevates the humerus. The extensor metacarpi radialis (EMR) is a small, pennate, distal forelimb muscle of the pigeon forelimb that functions in extending the wrist. We measured timing of motor-unit recruitment using electromyography and instantaneous length using sonomicrometry. Our results support the hypothesis that location and morphology of a muscle is indicative of its function. The proximal, parallel-fibered SHC underwent strains (relative length change) of 26% -30%, similar to those of the PECT (30% -38%). The distal, pinnate EMR underwent considerably less strain (11% -16%) in all modes of flight. Strain in the EMR was larger than what has been considered isometric in studies of terrestrial locomotion, which may indicate that the function of muscle is constrained in part by the substrate (air versus ground). Supported by NSF IOS-0923606 and IOS-0919799.
9:20 AM - 9:40 AM
Health professionals claim that those who are active will perform better cognitively. Researchers have shown that school aged children achieve higher GPAs when meeting the Surgeon Generals Guidelines for physical activity. Questions remain about the benefit of physical activity immediately before academic tests. Our goal was to analyze immediate cognitive responses following an acute bout of exercise. In trials, 68 voluntary participants (44 females, 24 males, 23.5 ± 3 years) completed both a sedentary and exercise trial, followed by a short academic test on different weeks. During the exercise trial, volunteers participated in 20 minutes of Zumba exercise and walked 5 minutes to a testing site. During the sedentary trial, participants sat for 25 minutes and listened to a collegiate lecture. For both trials, the participants completed a reading comprehension test made of 7 questions concerning 2 paragraphs of literature taken from practice GRE tests. Subjects also completed a questionnaire that included age, RPE during Zumba, food and caffeine intake, and hours of sleep. The overall test scores for the two trials were normalized to the first set of results to remove statistical error and then exercise and sedentary trials were compared with a dependent t-test with p<0.05. Results found there was a difference between the test scores of the sedentary and exercise test groups, with the sedentary group scoring slightly above the exercise group. The t-test, however, did not yield a statistically significant difference and does not disprove the positive impact of exercise on cognitive function.
9:40 AM - 10:00 AM
Centaurea solstitialis and Centaurea calcitrapa (yellow starthistle and purple starthistle) are two closely related species with highly overlapping native and non-native ranges in Spain and California, respectively. C. calcitrapa is naturalized but has not become invasive in California, whereas C. solstitialis has formed virtual monocultures in many parts of the state, decreasing both biodiversity and grazing potential. We sampled seeds from eight populations per species and region and grew plants alone and in competition with seven species of grasses from both ranges in a common garden greenhouse experiment. After 92 days plants were harvested, dried, and weighed. For both species, Californian populations were larger than Spanish conspecifics when grown with no competition. When plants were grown in competition with grasses, Californian populations of C. solstitialis out-performed their Spanish conspecifics, and in some cases competitors had no effect on North American C. solstitialis biomass. C. calcitrapa plants from California were consistently suppressed by competitors more than C. solstitialis, although plants from California tended to out-perform their Spanish conspecifics. Other studies indicate that some traits of C. solstitialis and C. calcitrapa have been selected for in their new, non-native ranges over the last two centuries. We cannot exclude potential founder effects, but our results suggest that such selection may extend to greater competitive abilities for both species in at least one non-native range. However, the invasive C. solstitialis demonstrated stronger competitive response to other species that the non-invasive C. calcitrapa, suggesting that inherent competitive abilities may contribute in part to invasiveness.
10:00 AM - 10:20 AM
Westslope cutthroat trout are a species of concern across all of their native range. It is estimated that westslope cutthroat currently occupy only 10 percent of their native range. One of the main reasons for their decline is hybridization with non-native rainbow trout. I looked at the ecological differences between hybrids and pure westslope cutthroat and rainbow trout. I have collected 200 samples over a 3 year period on the Jocko River basin in Western Montana. I will discuss the importance of migration timing in the spread of hybridization and examine whether environmental factors (stream flow and temperature), or population characteristics (size and age of fish or extent of hybridization) explain differences in migration timing for these species. I will also explore how much variation in growth rate exists across the years in relation to the extent of hybridization. Otoliths (the inner earbone of a fish) were extracted from all the samples and used to determine the age. I then back-calculated the proportional growth per year to see how much and how fast each individual was growing. I then compared this growth rate across individuals with varying degrees of hybridization to determine if hybridization is influencing growth rate. Westslope cutthroat have been petitioned for listing under the Endangered Species Act and have been repeatedly denied. Understanding what ecological differences exist between hybrids and pure westslope cutthroat and rainbow trout is an important step in developing a management strategy to deal with this threat.
10:20 AM - 10:40 AM
The Upper Clark Fork River Basin (UCFRB) is the largest Superfund site in the United States; the State of Montana is now in the process of remediating the damage following 100 years of mining from Butte westward. In order to develop reclamation plans, current conditions need to be clarified. Wildlife normally found in such riparian zones can be used as indicators of current conditions and provide a useful metric for success of remediation efforts. Beavers were one species that were historically abundant in this and similar ecosystems, but have appeared to decline over the past many decades. Beavers are an important species by serving as ecosystem engineers in such riparian ecosystems. Ecosystem engineers are animals that create or modify habitats. The purpose of this study was to determine how much beaver activity there is in the UCFRB between Warm Springs and Turah, Montana, and what the environmental characteristics of beaver habitation are in the UCFRB. We identified beaver activity by floating the river and marking the GPS coordinates for each active beaver lodge. We then determined which habitat characteristics are important for beaver occurrence by comparing 7 habitat variables which described topography, vegetation, and stream characteristics at 19 active beaver lodges and 22 random sites. Using an Analysis of Variance (ANOVA) to determine which characteristics are significantly different between active and random sites, we developed a predictive model for beaver activity. This research established a baseline of beaver activity throughout the UCFRB, and it identified which habitat characteristics are associated with beaver habitation in the UCFRB. Documenting their current populations will serve as a baseline to see how restoration affects river health and the expansion of this species.
10:40 AM - 11:00 AM
Mountain pine beetle (MPB) outbreaks are large-scale disturbances which can alter the structure and successional trajectory of affected forest stands. In mid-elevation ponderosa pine /mixed-conifer communities in particular, little is known about how different levels of MPB mortality will affect successional trajectories of affected forest stands, even though this forest type comprises large percentages of the western forest landscape. These forest stands may have a unique response to MPB mortality events compared to pure pine stands, due to the significant presence of non-host (non-pine) species.
To examine the effects of MPB outbreak on this forest type, forest inventory data collected from several stands recently affected by MPB was used to run a series of 50-year simulations using the U.S. Forest Service Forest Vegetation Simulator. Each stand was “grown” for 50 years under four different scenarios: no host species mortality, observed host species mortality, double observed host species mortality, and full host species mortality.
Simulations indicated shifts in stand structure aligned along a gradient of MPB intensity and persisting through time. At 50 years, under different beetle mortality scenarios, stands showed lower tree density (trees ha-1) and decreased basal area (m2 ha-1) compared to no-mortality scenarios. Non-host trees showed higher density and higher basal area compared to no-mortality scenarios. These results indicate that MPB may be a significant driver of stand structure and composition in mixed-conifer systems. By increasing understanding of the role of MPB on forest development, this information will help inform future forest management decisions involving MPB outbreaks.