Beyond R0 : demographic models for variability of lifetime reproductive output

© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 6 (2011): e20809, doi:10.1371/journal.pone.0020809.The net reproductive rate measures the expected lifetime reproductive output of an individual, and plays an important role in demography, ecology, evolution, and epidemiology. Well-established methods exist to calculate it from age- or stage-classified demographic data. As an expectation, provides no information on variability; empirical measurements of lifetime reproduction universally show high levels of variability, and often positive skewness among individuals. This is often interpreted as evidence of heterogeneity, and thus of an opportunity for natural selection. However, variability provides evidence of heterogeneity only if it exceeds the level of variability to be expected in a cohort of identical individuals all experiencing the same vital rates. Such comparisons require a way to calculate the statistics of lifetime reproduction from demographic data. Here, a new approach is presented, using the theory of Markov chains with rewards, obtaining all the moments of the distribution of lifetime reproduction. The approach applies to age- or stage-classified models, to constant, periodic, or stochastic environments, and to any kind of reproductive schedule. As examples, I analyze data from six empirical studies, of a variety of animal and plant taxa (nematodes, polychaetes, humans, and several species of perennial plants).Supported by National Science Foundation Grant DEB-0816514 and by a Research Award from the Alexander von Humboldt Foundation

Commitment of cultural minorities in organizations:Effects of leadership and pressure to conform

PURPOSE: In this study, we investigated the commitment of cultural minorities and majorities in organizations. We examined how contextual factors, such as pressure to conform and leadership styles, affect the commitment of minority and majority members. DESIGN/METHODOLOGY/APPROACH: A field study was conducted on 107 employees in a large multinational corporation. FINDINGS: We hypothesize and found that cultural minorities felt more committed to the organization than majority members, thereby challenging the existing theoretical view that cultural minorities will feel less committed. We also found that organizational pressure to conform and effective leadership increased the commitment of minorities. IMPLICATIONS: Our findings indicate that organizational leaders and researchers should not only focus on increasing and maintaining the commitment of minority members, but should also consider how majority members react to cultural socialization and integration processes. The commitment of minority members can be further enhanced by effective leadership. ORIGINALITY/VALUE: In this study, we challenge the existing theoretical view based on similarity attraction theory and relational demography theory, that cultural minorities would feel less committed to the organization. Past research has mainly focused on minority groups, thereby ignoring the reaction of the majority to socialization processes. In this study, we show that cultural minorities can be more committed than majority members in organizations. Therefore, the perceptions of cultural majority members of socialization processes should also be considered in research on cultural diversity and acculturation

Individual variability in the awareness of odors: demographic parameters and odor identification ability

Human chemosensation can be strongly influenced by how much attention people pay to chemosensory stimuli (e.g., Marks and Wheeler in Chem Senses 23:19–29, 1998; Prescott et al. in Chem Senses 29:331–340, 2004). In a recent study, a scale has been devised (i.e., the Odor Awareness Scale; OAS; see Smeets et al. in Chem Senses 33:725–734, 2008) to investigate the level of awareness people have of the available odorants in the environment. Here, we explored whether a variant (Italian version) of the OAS could be used to discriminate between different groups of participants in terms of olfactory abilities (i.e., performance in an odor identification task) and/or personal/demographic characteristics (e.g., gender, age, etc.). Ninety-eight participants underwent this study that was composed of a personal detail questionnaire, the OAS, and a deep investigation of odor identification ability based on a large variety of odor stimuli. During 6 testing sessions, a total of 72 odor stimuli were evaluated: 36 aromas in vapor phase presented in vials and 36 chemical compounds in hydroalcoholic solutions. The results did not indicate any relationships between the participants’ declared awareness of odors and the real performance in the identification test. However, differences in the awareness of odors were found as a function of a number of personal factors such as, for example, gender (with females showing higher scores than males) or age (with younger collecting lower scores than older participants). In conclusion, we could not predict from modified OAS scores the participants’ specific ability to identify odors. Nevertheless, we could extend the scale’s characterization by highlighting different connections between OAS scores and individual parameters