Determining carbon and nitrogen stable isotope discrimination for marine consumers

The application of stable isotope ratios to food web studies is increasing, and the use of generalised discrimination values (0.4±1.4%0 for δ13C and 3.4±1.1%0 for δ15N), which are being widely applied to many studies, may not be valid. The broad objective of this study was to evaluate the assumption that these discrimination values are applicable to a range of benthic marine consumers, and therefore appropriate to be used in trophic analyses using carbon (C) and nitrogen (N) stable isotopes in marine food webs. The first aim was to determine if there were differences in discrimination values: (1) among different groups of macroalgae when fed to specific consumers; and (2) among different types of consumers when fed on the same type of algae. The feeding treatments used representatives of brown, fleshy red, calcareous red and green macroalgal food sources, which were fed to three types of consumers: the sea urchin Heliocidaris e1ythrogramma, the hermit crabs Paguristes purpureantennatus and Calcinus dapsiles, and the gastropod Turbo torquatus. Food sources and consumers were collected from the field, and each food source was subsequently fed to each consumer in a series of controlled aquaria experiments. Replicate individuals of each consumer were sampled at regular intervals up to 56 days after initiation of the experiments. Muscle tissue was processed and analysed using mass spectrometry to determine δ13C and δ15N values. In accordance with the feeding treatments, starvation treatments were also conducted. The results showed a general trend of no change in δ13C and δ15N isotope ratios for the invertebrate consumers over time, and this was also the case for the starvation treatments. Observations during the experiments indicated that animals were active and consuming the algae in the feeding treatments compared to the starved invertebrates which remained relatively immobile. Constant feeding by invertebrates suggests that discrimination values derived from the experiment are likely to be realistic. Results indicated that δ13C and δ15N discrimination differed among groups of algae, particularly for carbon. Average δ13C discrimination values were 1.56%0 for brown algae, 2.31 %0 for fleshy red algae, 3.38%0 for calcareous red algae, 1.46%0 for green algae, while average δ15N discrimination values were 2.6­0%0, 2.03%0, 2.53%0, and 2.93%0 for the respective algal groups. δ13C and δ15N discrimination also differed among consumers when fed on the same food source. Average δ13C discrimination values were 2.67%0, 2.70%0, 2.58%0 and 1.31 %0 for the urchin Herythrogramma, the hermit crabs P. purpureantennatus and C. dapsiles and the gastropod T torquatus, respectively, while average δ15N discrimination values were 3.14%0, 3.80%0, 2.15%0 and 1.31%0 for the respective species. Thus, the results of this study indicate that different discrimination values are exhibited for different algal food sources and by different consumers under the environmental conditions within this study. Furthermore these values differed from the assumed discrimination values that are applied to many stable isotope studies. In many isotope-based food web studies, mixing models are utilised to quantify the possible contributions of different food sources to a consumer\u27s diet. This process has better outcomes than traditional gut content analysis, as it reflects actual assimilation of food sources rather than what material is found in the gut tract. The second aim was to compare results of the Isosource mixing model when using either assumed or experimentally-derived discrimination values to evaluate the contribution of the different macroalgal species to the natural diets of marine invertebrates. The assumed discrimination values of 0.4%0 for δ13C and 3.4%0 for δ15N were applied to the food source stable isotope dataset as input data for Isosource, and compared to results when the experimentally derived values were applied to the same dataset. Results from Isosource were not possible using the assumed values, due to the isotope ratios of consumers sitting outside the range of sources. However when the experimentally derived discrimination values were applied, the model ran successfully. These mixing model results indicated that brown, red and green algae all contributed to the production of consumers, but there were differences in the relative contributions of these food sources among the consumer species examined. The current study has quantified C and N discrimination for key marine invertebrate and algal types, and particularly for C these values were found to be higher (1.46-3.38%0) than those generally applied, i.e. 0.4 ± 1.4%0. The assumed discrimination values are not applicable across all food sources or consumer groups. The consequences of applying incorrect discrimination values include preventing any sources of production to be established, or leading to erroneous conclusions about an organism\u27s trophic level or food source

Re-examining the implications of systems thinking for evaluation

Over the last twenty years, many prominent evaluators have been borrowing and using ideas, theories, and methods from the systems and complexity fields with little research on the implications of this trend for the evaluation field. This thesis examines this borrowing to identify over-arching implications for evaluation theory and practice. The first paper reviews inter-disciplinary literature on systems thinking and complexity science with regards to evaluating social policies and programs and identifies major implications for how evaluators theorize evaluation practice. The second paper reports on an analysis of eight cases of evaluation practice that use systems and complexity ideas and techniques and presents findings regarding how evaluators conceive of and practice evaluation. The third paper advances an argument for how evaluators can use critical systems heuristics to surface, reflect on, and make explicit the values that influence and should influence an evaluation. Collectively, these papers support the potential of borrowing from the systems and complexity fields to expand on and re-define evaluation theory and practice

Anecdotes and Opinions: Examining Evidence Generated by Group Interview Methods

People’s thoughts and opinions are formed by experience – their personal contact with and observations of people and events. Focus groups are often used in evaluation as a qualitative method to collect information about people’s experience. Focus groups traditionally capture experience by soliciting thoughts and opinions rather than stories. In some cases, program evaluations that seek to understand participants’ experiences may find more meaningful evidence in participants’ narrative descriptions of their experiences in the program, rather than their thoughts or opinions about the program. Anecdote circles, a group interview method from the field of business, gather evidence about participants’ experience by posing questions that invite storytelling. This paper describes a study that compares the characteristics of the evidence generated by focus group prompts that elicit thoughts or opinions and anecdote circle prompts that elicit stories in the context of an evaluation of a cross-cultural institute for high school teachers.Ope

Equity “On the Sideline”: A Mixed Methods Study of New England Evaluation Practice in 2020

Background: Centering equity in evaluations is increasingly recognized as an important professional responsibility of evaluators. While some theoretical and practical guidance exists, the evaluation field has limited empirical research on equity within evaluation practice. Purpose: This paper explores whether and how evaluators address inequities and advance equity throughout evaluation phases drawing on select findings from a larger study. Setting: The study focuses on American Evaluation Association-affiliated evaluators in the New England region of the United States who work in a variety of areas (e.g., health, education).   Intervention: Not applicable Research Design: The study uses a complementarity, sequential mixed methods design comprised of a researcher-developed online questionnaire administered to a census and snowball sample of practicing evaluators (n=82) and individual, semi-structured interviews with a subset of this sample selected to maximize variation (n=21). Quantitative data were analyzed using descriptive statistics (i.e., means and standard deviations, frequencies). Qualitative data were analyzed using a collaborative process of deductive and inductive coding followed by thematic analysis. Findings: Eight overarching findings suggest that despite evaluators’ attempts to center equity, it remains largely “on the sideline.” This is due to evaluators’ need to work against some conventional professional and methodological norms, within contractual and contextual constraints, and with limited professional preparation. &nbsp

MBNL1 binds GC motifs embedded in pyrimidines to regulate alternative splicing

Muscleblind-like 1 (MBNL1) regulates alternative splicing and is a key player in the disease mechanism of myotonic dystrophy (DM). In DM, MBNL1 becomes sequestered to expanded CUG/CCUG repeat RNAs resulting in splicing defects, which lead to disease symptoms. In order to understand MBNL1’s role in both the disease mechanism of DM and alternative splicing regulation, we sought to identify its RNA-binding motif. A doped SELEX was performed on a known MBNL1-binding site. After five rounds of SELEX, MBNL1 selected pyrimidine-rich RNAs containing YGCY motifs. Insertion of multiple YGCY motifs into a normally MBNL1-independent splicing reporter was sufficient to promote regulation by MBNL1. MBNL1 was also shown to regulate the splicing of exon 22 in the ATP2A1 pre-mRNA, an exon mis-spliced in DM, via YGCY motifs. A search for YGCY motifs in 24 pre-mRNA transcripts that are mis-spliced in DM1 patients revealed an interesting pattern relative to the regulated exon. The intronic regions upstream of exons that are excluded in normal tissues relative to DM1, are enriched in YGCY motifs. Meanwhile, the intronic regions downstream of exons that are included in normal tissues relative to DM1, are enriched in YGCY motifs

Multisystem Proteinopathy Mutations in VCP/p97 Increase NPLOC4·UFD1L Binding and Substrate Processing

Valosin-containing protein (VCP)/p97 is an essential ATP-dependent protein unfoldase. Dominant mutations in p97 cause multisystem proteinopathy (MSP), a disease affecting the brain, muscle, and bone. Despite the identification of numerous pathways that are perturbed in MSP, the molecular-level defects of these p97 mutants are not completely understood. Here, we use biochemistry and cryoelectron microscopy to explore the effects of MSP mutations on the unfoldase activity of p97 in complex with its substrate adaptor NPLOC4⋅UFD1L (UN). We show that all seven analyzed MSP mutants unfold substrates faster. Mutant homo- and heterohexamers exhibit tighter UN binding and faster substrate processing. Our structural studies suggest that the increased UN affinity originates from a decoupling of p97's nucleotide state and the positioning of its N-terminal domains. Together, our data support a gain-of-function model for p97-UN-dependent processes in MSP and underscore the importance of N-terminal domain movements for adaptor recruitment and substrate processing by p97

Multisystem Proteinopathy Mutations in VCP/p97 Increase NPLOC4·UFD1L Binding and Substrate Processing

Valosin-containing protein (VCP)/p97 is an essential ATP-dependent protein unfoldase. Dominant mutations in p97 cause multisystem proteinopathy (MSP), a disease affecting the brain, muscle, and bone. Despite the identification of numerous pathways that are perturbed in MSP, the molecular-level defects of these p97 mutants are not completely understood. Here, we use biochemistry and cryoelectron microscopy to explore the effects of MSP mutations on the unfoldase activity of p97 in complex with its substrate adaptor NPLOC4⋅UFD1L (UN). We show that all seven analyzed MSP mutants unfold substrates faster. Mutant homo- and heterohexamers exhibit tighter UN binding and faster substrate processing. Our structural studies suggest that the increased UN affinity originates from a decoupling of p97's nucleotide state and the positioning of its N-terminal domains. Together, our data support a gain-of-function model for p97-UN-dependent processes in MSP and underscore the importance of N-terminal domain movements for adaptor recruitment and substrate processing by p97

Equity “On the Sideline”

Background: Centering equity in evaluations is increasingly recognized as an important professional responsibility of evaluators. While some theoretical and practical guidance exists, the evaluation field has limited empirical research on equity within evaluation practice. Purpose: This paper explores whether and how evaluators address inequities and advance equity throughout evaluation phases drawing on select findings from a larger study. Setting: The study focuses on American Evaluation Association-affiliated evaluators in the New England region of the United States who work in a variety of areas (e.g., health, education).   Intervention: Not applicable Research Design: The study uses a complementarity, sequential mixed methods design comprised of a researcher-developed online questionnaire administered to a census and snowball sample of practicing evaluators (n=82) and individual, semi-structured interviews with a subset of this sample selected to maximize variation (n=21). Quantitative data were analyzed using descriptive statistics (i.e., means and standard deviations, frequencies). Qualitative data were analyzed using a collaborative process of deductive and inductive coding followed by thematic analysis. Findings: Eight overarching findings suggest that despite evaluators’ attempts to center equity, it remains largely “on the sideline.” This is due to evaluators’ need to work against some conventional professional and methodological norms, within contractual and contextual constraints, and with limited professional preparation.

Resilience - towards an interdisciplinary definition using information theory

The term “resilience” has risen in popularity following a series of natural disasters, the impacts of climate change, and the Covid-19 pandemic. However, different disciplines use the term in widely different ways, resulting in confusion regarding how the term is used and difficulties operationalising the underlying concept. Drawing on an overview of eleven disciplines, our paper offers a guiding framework to navigate this ambiguity by suggesting a novel typology of resilience using an information-theoretic approach. Specifically, we define resilience by borrowing an existing definition of individuals as sub-systems within multi-scale systems that exhibit temporal integrity amidst interactions with the environment. We quantify resilience as the ability of individuals to maintain fitness in the face of endogenous and exogenous disturbances. In particular, we distinguish between four different types of resilience: (i) preservation of structure and function, which we call “strong robustness”; (ii) preservation of function but change in structure (“weak robustness”); (iii) change in both structure and function (“strong adaptability”); and (iv) change in function but preservation in structure (“weak adaptability”). Our typology offers an approach for navigating these different types and demonstrates how resilience can be operationalised across disciplines