Compartments in food webs are subgroups of taxa in which many strong interactions occur within the subgroups and few weak interactions occur between the subgroups. Theoretically, compartments increase the stability in networks, such as food webs. Compartments have been difficult to detect in empirical food webs because of incompatible approaches or insufficient methodological rigour. Here we show that a method for detecting compartments from the social networking science identified significant compartments in three of five complex, empirical food webs. Detection of compartments was influenced by food web resolution, such as interactions with weights. Because the method identifies compartmental boundaries in which interactions are concentrated, it is compatible with the definition of compartments. The method is rigorous because it maximizes an explicit function, identifies the number of non-overlapping compartments, assigns membership to compartments, and tests the statistical significance of the results. A graphical presentation reveals systemic relationships and taxa-specific positions as structured by compartments. From this graphic, we explore two scenarios of disturbance to develop a hypothesis for testing how compartmentalized interactions increase stability in food webs.

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Background/Context Researchers have proposed a number of lenses for analyzing teacher professional communities in recent years. These lenses have been useful in describing key dynamics of professional communities; however, none provides a compelling approach to how to integrate data from the school as a whole with case study data on individual interactions to create a coherent account of the structure and dynamics of teacher professional communities. Objective Our objective was to present and illustrate the application of social capital theory for analyzing the role of formal and informal teacher interactions in helping teachers enact changes to instruction associated with ambitious school reforms. Social capital theory posits that valued resources and expertise are embedded within social networks and that it is through social ties that one gains access to and can make use of resources to effect change. The network perspective directs researchers to focus simultaneously on the overall social structure of a school and on the expertise and resources exchanged through interactions among teachers that take place in meetings, staff rooms, hallways, and classrooms. Setting Our illustrations are contrasting cases of teacher communities in two elementary schools in California. In both school communities, the principals were committed to the idea of fostering greater interaction among colleagues as a strategy to improve literacy instruction. Both schools had similar levels of resources to support their goals through external funding from the state, but the schools had had different levels of success in implementing their reforms at the time of the study. Research Design We used an explanatory case study methodology that relied on social network, survey, and interview methods as sources of evidence for several alternative hypotheses relating to how the distribution of resources and expertise may have contributed to these schools’ different levels of success in implementing their reforms. Conclusions/Recommendations The comparative case analysis of the two schools provided evidence that analyzing the internal structure of the school community was necessary to help account for the distribution of access to resources and expertise in these two schools. Moreover, there was some evidence from survey and network data that the distribution of valued resources and expertise was related to the level of change observed in each school.

After a 40-year absence caused by pollution and eutrophication, burrowing mayflies (Hexagenia spp.) recolonized western Lake Erie in the mid 1990s as water quality improved. Mayflies are an important food resource for the economically valuable yellow perch fishery and are considered to be major indicator species of the ecological condition of the lake. Since their reappearance, however, mayfly populations have suffered occasional unexplained recruitment failures. In 2002, a failure of fall recruitment followed an unusually warm summer in which western Lake Erie became temporarily stratified, resulting in low dissolved oxygen levels near the lake floor. In the present study, we examined a possible link between Hexagenia recruitment and periods of intermittent stratification for the years 1997 2002. A simple model was developed using surface temperature, wind speed, and water column data from 2003 to predict stratification. The model was then used to detect episodes of stratification in past years for which water column data are unavailable. Low or undetectable mayfly recruitment occurred in 1997 and 2002, years in which there was frequent or extended stratification between June and September. Highest mayfly reproduction in 2000 corresponded to the fewest stratified periods. These results suggest that even relatively brief periods of stratification can result in loss of larval mayfly recruitment, probably through the effects of hypoxia. A trend toward increasing frequency of hot summers in the Great Lakes region could result in recurrent loss of mayfly larvae in western Lake Erie and other shallow areas in the Great Lakes.

In addition to identifying and developing superior classroom teaching, the National Board for Professional Teaching Standards (NBPTS) certification process is intended to identify and cultivate teachers who are more engaged in their schools. Here the authors ask, “Does NBPTS certification affect the number of colleagues a teacher helps with instructional matters?” If so, this could enhance the influence of NBPTS-certified teachers and their contributions to their professional communities. Using sociometric data within 47 elementary schools from two states, the authors find that NBPTS-certified teachers were nominated more as providing help with instruction than non-NBPTS-certified teachers. From analyses using propensity score weighting, the authors then infer that NBPTS certification affects the number of colleagues a teacher helps with instructional matters. The authors then quantify the robustness of their inference in terms of internal and external validity, finding, for example, that any omitted confounding variable would have to have an impact six times larger than that of their strongest covariate to invalidate their inference. Therefore, the potential value added by NBPTS-certified teachers as help providers has policy and practice implications in an era when teacher leadership has risen to the fore as a critical force for school improvement.