Reciprocal subsidies in a fourth order Rocky Mountain stream

Includes bibliographical references.2015 Summer.To view the abstract, please see the full text of the document

Bayesian hierarchical modelling of size spectra

A fundamental pattern in ecology is that smaller organisms are more abundant than larger organisms. This pattern is known as the individual size distribution (ISD), which is the frequency distribution of all individual body sizes in an ecosystem. The ISD is described by a power law and a major goal of size spectra analyses is to estimate the exponent of the power law, λ. However, while numerous methods have been developed to do this, they have focused almost exclusively on estimating λ from single samples. Here, we develop an extension of the truncated Pareto distribution within the probabilistic modelling language Stan. We use it to estimate multiple λs simultaneously in a hierarchical modelling approach. The most important result is the ability to examine hypotheses related to size spectra, including the assessment of fixed and random effects, within a single Bayesian generalized mixed model. While the example here uses size spectra, the technique can also be generalized to any data that follow a power law distribution

The Power of Play: A Pediatric Role in Enhancing Development in Young Children

Children need to develop a variety of skill sets to optimize their development and manage toxic stress. Research demonstrates that developmentally appropriate play with parents and peers is a singular opportunity to promote the social-emotional, cognitive, language, and self-regulation skills that build executive function and a prosocial brain. Furthermore, play supports the formation of the safe, stable, and nurturing relationships with all caregivers that children need to thrive

Body size distributions and diet breadth : stream food web proxies and predictions across a contaminant gradient

Ecological networks, such as food webs, offer a powerful framework for understanding the structure, function, and stability of biotic communities. However, logistical constraints related to traditional food web construction methods restrict their widespread use in ecological studies. Alternative methods, such as size spectra analysis, exist which incorporate much of the variation in food web structure, but are easier to measure. Additionally, advances in mechanistic models allow for the inference of pairwise species interactions, potentially scaling up to whole-network level measures. The aim of my thesis was to investigate the utility of several of these alternative approaches in determining food web structures in degraded ecosystems. In particular, streams impacted by Acid Mine Drainage from coal mining. Firstly, I conducted a field survey of 25 stream communities across a gradient of acid mine drainage (AMD) inputs on the West Coast of the South Island, New Zealand. Comparative size spectra analysis revealed consistent changes to the size spectra relationship across the gradient. Size spectra intercepts, or total community abundance, were significantly reduced along the gradient. The slopes of size spectra increased significantly across the gradient from ~ -1.1 to ~ -0.6, meaning that the proportion of large to small bodied individuals decreased less rapidly in effected streams. Size spectra slopes are related to trophic transfer efficiency, and shallower slopes observed in AMD impacted streams indicate a reduced transfer efficiency. Furthermore, both the largest and smallest body size classes were removed from the most heavily impacted streams, leading to a reduction in the range of body sizes present by up to two orders of magnitude. Most aquatic food webs are size-structured, with body size and trophic level generally being positively correlated. Therefore, changes in the distribution of body sizes has significant implications for food-web structure. Another alternative to traditional food web construction is the use of models and inference techniques to predict food web structure. I developed a novel model to predict pairwise species interactions within communities. This model is mechanistic, and predicts the ability of species to interact based on observed distributions of species traits (e.g. body size). These predictions are further refined by taking into account local population densities (e.g. rare species less likely to interact). This model successfully predicted pairwise species interactions in streams across land use types. Importantly, successfully predicting interactions between species also “scaled up” and accurately predicted the structure of the whole food web. A further derivation of this model was used to infer the structure and stability of stream food webs using empirical data on communities across an AMD gradient. The model was modified from above in order to predict interaction probabilities, as opposed to link presence/absence. By using interaction probabilities, it is possible to assess how variable trophic interactions within a community affect estimates of stability. Generally, food webs become small and more stable in response to increasing AMD impacts. However, the distribution of the stability metric assessed appears to become bimodal, depending on how interaction strengths are estimated. This has implications on the restoration of streams impacted by AMD, suggesting that some streams may be more easily colonized by extirpated sensitive species post-restoration activities. Overall, my findings have increased our understandings of the impacts of AMD to stream communities. Furthermore, they support the use of alternative methods, such as size spectra analysis, in biomonitoring surveys. The method developed for inferring food web structure has the potential to allow ecologists to rapidly assess likely food-web structure across large spatial or temporal scales, aiding in the ability to test ecological theories. Finally, the use of probabilistic networks to assess network structure represent an important step in taking into account the inherent variability of species interactions in ecological studies

Data from: Inferring predator-prey interactions in food webs

1. Food webs are a powerful way to represent the diversity, structure, and function of ecological systems. However, the accurate description of food webs requires significant effort in time and resources, limiting their widespread use in ecological studies. Newly published methods allow for the inference of feeding interactions using proxy variables. Here, we compare the accuracy of two recently described methods, as well as describe a composite model of the two, for the inference of feeding interactions using a large, well-described dataset. 2. Both niche and neutral processes are involved in determining whether or not two species will form a feeding link in communities. Three different models for determining niche constraints of feeding interactions are compared, and all three models are extended by incorporating neutral processes, based on relative abundances. The three models compared here infer niche processes through 1) phylogenetic relationships, 2) local species trait distributions (e.g. body size), and 3) a composite of phylogeny and local traits. 3. We show that all three methods perform well at predicting individual species interactions, and that these individual predictions scale up to the network level, resulting in food-web structure of inferred networks being similar to their empirical counterparts. 4. Our results indicate that inferring food-web structure using phylogenies can be an efficient way of getting summary webs with minimal data, and offers a conservative test of changes in food-web structure, particularly when there is low species turnover between sites. Inferences made using traits requires more data, but allows for greater understanding of the mechanisms underlying trophic interactions. A composite model of the two methods provides a framework for investigating the importance of how phylogeny, trait distributions, and relative abundances, affect species interactions, and network structure

estimated_dw

This file contains the estimated dry weight for all individual macroinvertebrates collected across 25 streams in New Zealand. Below are the column names and a brief description of them. site = Site name; character string. surber = Surber sample that individual was collected in (s1, s2, or s3). linear_meas = linear measurement of the individual in millimeters. dw = estimated dry weight of individual in units of grams. FFG = functional feeding group; CB = collector browser, G = grazer, P = predator, FF = filter feeder, S = shredder, O = omnivore, NA = unknown

Individual size distributions across North American streams vary with local temperature

Parameters describing the negative relationship between abundance and body size within ecological communities provide a summary of many important biological processes. While it is considered to be one of the few consistent patterns in ecology, spatiotemporal variation of this relationship across continental scale temperature gradients is unknown. Using a database of stream communities collected across North America (18-68° N latitude, -4 to 25°C mean annual air temperature) over 3 years, we constructed 160 individual size distribution relationships (i.e. abundance size spectra). The exponent parameter describing ISD\u27s decreased (became steeper) with increasing mean annual temperature, with median slopes varying by ~0.2 units across the 29°C temperature gradient. In addition, total community biomass increased with increasing temperatures, contrary to theoretical predictions. Our study suggests conservation of individual size distribution relationships in streams across broad natural environmental gradients. This supports the emerging use of size-spectra deviations as indicators of fundamental changes to the structure and function of ecological communities

other_feeding_interactions

This file contains data on published feeding interactions from New Zealand streams. Each row represents a consumer-resource interaction, and contains phylogenetic information for both the consumer and resource. The "res." prefix in columns indicates that column refers to the resource, and the "con." prefix refers to data on the consumer. The "source.id" column indicates the original citation for where the data came from