Isotopic Niche Partitioning and Individual Specialization in an Arctic Raptor Guild

Intra- and inter-specific resource partitioning within predator communities is a fundamental component of trophic ecology, and one proposed mechanism for how populations partition resources is through individual niche variation. The Niche Variation Hypothesis (NVH) predicts that interindividual trait variation leads to functional trade-offs in foraging efficiency, resulting in populations comprised of individual dietary specialists. A modified version of the NVH [mNVH] predicts niche specialization is plastic and responsive to fluctuating resource availability. We quantified niche overlap and tested the mNVH within an Arctic raptor guild, focusing on three species that employ different foraging strategies: Golden Eagles (generalists); Gyrfalcons (facultative specialists); and Rough-legged Hawks (specialists). Tundra ecosystems exhibit cyclic populations of arvicoline rodents (lemmings and voles), providing a unique system under which to examine interannual fluctuations in predator resource availability. Using blood δ13C & δ15N values from 189 raptor nestlings on Alaska’s Seward Peninsula (2014–2019), we calculated isotopic niche width and used Bayesian stable isotope mixing models (BSIMMs) to characterize individual specialization and test the mNVH. We observed a high degree of isotopic niche overlap between the three species and variable trophic responses to different stages of the arvicoline rodent cycle. Elevated arvicoline rodent abundance corresponded to reduced niche overlap among species and increased individual specialization in Golden Eagles and Gyrfalcons. Further, Gyrfalcons displayed a positive relationship between individual specialization and population niche width on an interannual basis consistent with the mNVH. Our findings suggest plasticity in niche specialization may reduce intra- and inter-specific resource competition under dynamic ecological conditions.

Generalist populations formed by generalist individuals: a case of study on the feeding habits of a Neotropical stream fish

Aim We described the diet of the generalist stream fish Knodus chapadae and we tested if the environmental conditions are associated with population’s diet and individual specialization. Methods We analyzed the stomach contents of 287 individuals from 29 streams from the Brazilian savanna (Cerrado). Results The instream physical habitat structure, physiochemical conditions, and adjacent land use explained partially the variation in the diet of populations, but not the variation in the individual specialization. Thus, the diet changes observed at populational level were driven by changes in the average composition of the diet of individuals that, in turn, remained generalists along the environmental gradient. Conclusions Our results show that the trophic opportunism described for small characids was also observed in K. chapadae, whose diet shifts according to changes in environmental conditions. Furthermore, the opportunism expressed at the individual level can explain the trophic plasticity observed on the studied species.

Personalkonflikter i kirkens arbeidsmiljø som en ledelsesutfordring

The perception that conflicts are unavoidable and natural derives from paradoxical developments in modern work life, with increasing cooperation, democratization, and individual specialization. This chapter asks: How have workplace conflicts been conceptualized and managed within the Church of Norway in the period 1980–2020? We identify three connected concepts key to conflicts: prevention, understanding, and management. These have been adopted from the general literature and applied in the church context. We analyse how conflicts relate to structural and cultural features within the church. From being implicit and largely left to the involved parties, we describe and discuss implications of how conflicts have become a managerial responsibility, in accordance with the Work Environment Law.

Individual dietary specialization reduces intraspecific competition, rather than feeding activity, in black amur bream (Megalobrama terminalis)

Individual specialization and high plasticity in feeding activity are common in natural populations. However, the role of these two in intraspecific competition is unclear. In this study, the rhythm of feeding activity, dietary composition, niche width, niche overlap, and individual specialization was explored in four different size groups of black amur bream (Megalobrama terminalis), using microscopic identification of foregut contents and stable isotope analysis (δ13C and δ15N) of dorsal muscle. Both methods observed ontogenetic shifts in dietary preference and individual specializations, and revealed that the total niche width of large individuals was greater than small individuals. Mixed linear models indicated that feeding activity was significantly influenced by time (p < 0.0001), and no significant changes among size groups was evident (p = 0.244). Niche overlaps revealed that there was intensive diet competition between different size groups of black amur bream. Individual specialization in small juveniles was likely to be stronger than sub-adult and adult groups. Pearson’s correlation analysis revealed that the individual specialization was positively correlated with mean diet similarity within a group. The results indicated that intraspecific competition is reduced mainly by individual dietary specialization, rather than shift in feeding activity.

Network representations of diversity in scientific teams

One strength of network analysis is its ability to encapsulate social heterogeneity. Here, we leverage that strength to examine another dimension of individual heterogeneity: heterogeneity of skills, knowledge and experience. This skill heterogeneity is difficult to quantify, but is vitally important to outcomes for both individuals and teams. Complicating the matter, skill diversity can be present on multiple levels. Individuals have different kinds of skills, but they also have different degrees of specialization. Skill diversity on a team level may come from individual skill diversity or focused researchers in different areas. Here, we illustrate our network-based method for characterizing skill sets in a context of increasing importance: scientific collaboration. Using data from the field of economics, we create network-based measures of paper scope, individual specialization, coauthor alignment and team skill diversity. We then use those measures to examine the relationship between skill diversity and publication outcomes.