Simulating Food Web Dynamics along a Gradient: Quantifying Human Influence

Realistically parameterized and dynamically simulated food-webs are useful tool to explore the importance of the functional diversity of ecosystems, and in particular relations between the dynamics of species and the whole community. We present a stochastic dynamical food web simulation for the Kelian River (Borneo). The food web was constructed for six different locations, arrayed along a gradient of increasing human perturbation (mostly resulting from gold mining activities) along the river. Along the river, the relative importance of grazers, filterers and shredders decreases with increasing disturbance downstream, while predators become more dominant in governing eco-dynamics. Human activity led to increased turbidity and sedimentation which adversely impacts primary productivity. Since the main difference between the study sites was not the composition of the food webs (structure is quite similar) but the strengths of interactions and the abundance of the trophic groups, a dynamical simulation approach seemed to be useful to better explain human influence. In the pristine river (study site 1), when comparing a structural version of our model with the dynamical model we found that structurally central groups such as omnivores and carnivores were not the most important ones dynamically. Instead, primary consumers such as invertebrate grazers and shredders generated a greater dynamical response. Based on the dynamically most important groups, bottom-up control is replaced by the predominant top-down control regime as distance downstream and human disturbance increased. An important finding, potentially explaining the poor structure to dynamics relationship, is that indirect effects are at least as important as direct ones during the simulations. We suggest that our approach and this simulation framework could serve systems-based conservation efforts. Quantitative indicators on the relative importance of trophic groups and the mechanistic modeling of eco-dynamics could greatly contribute to understanding various aspects of functional diversity

Stable Isotope Evidence for Dietary Overlap between Alien and Native Gastropods in Coastal Lakes of Northern KwaZulu-Natal, South Africa

Tarebia granifera (Lamarck, 1822) is originally from South-East Asia, but has been introduced and become invasive in many tropical and subtropical parts of the world. In South Africa, T. granifera is rapidly invading an increasing number of coastal lakes and estuaries, often reaching very high population densities and dominating shallow water benthic invertebrate assemblages. An assessment of the feeding dynamics of T. granifera has raised questions about potential ecological impacts, specifically in terms of its dietary overlap with native gastropods.A stable isotope mixing model was used together with gut content analysis to estimate the diet of T. granifera and native gastropod populations in three different coastal lakes. Population density, available biomass of food and salinity were measured along transects placed over T. granifera patches. An index of isotopic (stable isotopes) dietary overlap (IDO, %) aided in interpreting interactions between gastropods. The diet of T. granifera was variable, including contributions from microphytobenthos, filamentous algae (Cladophora sp.), detritus and sedimentary organic matter. IDO was significant (>60%) between T. granifera and each of the following gastropods: Haminoea natalensis (Krauss, 1848), Bulinus natalensis (Küster, 1841) and Melanoides tuberculata (Müller, 1774). However, food did not appear to be limiting. Salinity influenced gastropod spatial overlap. Tarebia granifera may only displace native gastropods, such as Assiminea cf. ovata (Krauss, 1848), under salinity conditions below 20. Ecosystem-level impacts are also discussed.The generalist diet of T. granifera may certainly contribute to its successful establishment. However, although competition for resources may take place under certain salinity conditions and if food is limiting, there appear to be other mechanisms at work, through which T. granifera displaces native gastropods. Complementary stable isotope and gut content analysis can provide helpful ecological insights, contributing to monitoring efforts and guiding further invasive species research

MUSCLE COMPOSITION AND PERFORMANCE IN MALE AND FEMALE PREPUBESCENT YOUTH

Rosemary Sisillo1, Makenzie E. Kerans1, Jackson R. Dinsmore2, Trent J. Herda2, and Ashley A. Herda1 1University of Kansas-Edwards Campus, Overland Park, KS; 2University of Kansas-Lawrence Campus, Lawrence, KS PURPOSE: The purpose of this study is to identify the relationships among thigh muscle composition and sprint speed in young males and females. METHODS: Fourteen young (range: 5-11 years) males (n=9) and females (n=5) were measured for height, weight, and seated height to determine leg length and maturation. Skinfold thickness of the right tricep and subscapular regions were measured to estimate body fat percentage. Additionally, an ultrasound image of the right quadriceps vastus lateralis (VL) muscle was recorded and analyzed for VL thickness (VLTHK), cross-sectional area (VLCSA), and subcutaneous fat (VLFAT). Participants performed a 10-meter sprint on a 25m marked turf course. The first 10mwere dedicated to acceleration, timing gates were set at the 10m and 20m marks and the final 5m was used for deceleration. Stepwise linear regression was used to determine prediction of the 10m sprint using anthropometric and muscle composition data. Additionally, Pearson correlation coefficients were determined between sprint speed and muscle composition. RESULTS: The results of the linear regression analysis indicated age, leg length, and VLFAT were the primary predictors of 10-meter sprint time (R2=0.916; p\u3c0.05). Cross-validation with a second group of individuals(5-11 years; n=7) resulted in a strong correlation between the actual 10m sprint time and predicted time (r=0.87, p=0.01) and a paired t-test indicated no difference between the predicted and actual 10m sprint time (mean diff=0.02s, p=0.70). Top speed (m/s) during the 10m sprint speed was correlated to VL thickness (r=0.56, p=0.04) and leg length (r=0.56, p=0.04) whereas the 10m sprint time was correlated with VLCSA (r=0.621, p=0.02). CONCLUSION: Application of anthropometric and muscle composition data to predict performance would be simple and non-exertive during recovery if a young athlete were injured and undergoing a rehabilitation protocol. These measurements also assist in determining sport specificity as they mature and begin to specialize in endurance, speed, or strength-based activities. Caution for this prediction should be exercised as this study used a relatively small sample to estimate the 10m sprint. Body composition should not be the primary focus at such a young age, rather skill development to optimize performance and reduce injury

Participation in publishing:The demoralizing discourse of disadvantage

The dominance of English in global academic publishing has raised questions of communicative inequality and the possible ‘linguistic injustice’ against an author’s mother tongue. Native English speakers are thought to have an advantage as they acquire the language naturalistically while second language users must invest more time, effort and money into formally learning it and may experience greater difficulties when writing in English. Surveys reveal that English as an Additional Language authors often believe that editors and referees are prejudiced against them for any non-standard language. In this paper I critically review the evidence for linguistic injustice through a survey of the literature and interviews with scholars working in Hong Kong. I argue that framing publication problems as a crude native vs non-native polarisation not only draws on an outmoded respect for ‘native speaker’ competence but serves to demoralizes EAL writers and marginalize the difficulties experienced by novice L1 English academics. The paper, then, is a call for a more inclusive and balanced view of academic publishing