Jesús Piqueras

Demography and modelling of clonal fragments in the pseudoannual plant shape Trientalis europaea L.

The clonal growth pattern and demography of clonal fragments (aggregation of ramets derived from a common parent ramet) in the pseudoannual plant Trientalis europaea were studied in field conditions from 1991 to 1993. During this period the population of clonal fragments declined, with a half-life of 7.4 years. Number and size of the clonal progeny and stolon length were positively related to the size of the mother ramet. Survival rates of ramets and tubers increased with size. The rate of clonal growth was low: after three years, about 70% of the clonal fragments had only one ramet. This suggests that the pseudoannual growth habit in T. europaea is more important as mechanism of perennation than of ramet multiplication.Field data were used in a simulation model of architecture and population dynamics of clonal fragments. About 10% of the clonal fragments survived to the end of the simulation (15 years) and the mean survival was 4.7 years. The model predicted a positive correlation between persistence of the clonal fragment and number of ramets produced. Sensitivity analysis showed that the production of a daughter ramet of at least the same size as the parent ramet was the most important pathway for the survival and the number of ramets of the clonal fragment, whereas the production of secondary ramets had a very small effect. This confirms the interpretation of the pseudoannual life-cycle as a mechanism of ramet replacement in this species. Sensitivity analysis also revealed that changes in survival probabilities of the smallest ramets had the largest impact on clonal fragment dynamics. This reflects the important role of the smallest size class of ramets as a source of new vegetative propagules, maintaining a hierarchy in the size structure of the population.

Student Teachers’ Moment-to-Moment Reasoning and the Development of Discursive Themes – an Analysis of Practical Epistemologies in a Natural History Museum Exhibit

The development of socio-cultural perspectives in education has involved an expansion of the research scope on learning, from being focused primarily on individuals’ cognition, to an emphasis on the role of communication and its historical, situational and cultural features (Lave & Wenger, 1991; Rogoff, 1995; Saljo, 2000; Wertsch, 1991; Wickman, 2004).The philosophical orientation of pragmatism, as developed for research in science education, has further added to this approach by providing ways of handling learning in terms of language use and meaning, and as part of whole activities having purposes (Almqvist & Ostman, 2006; Gyllenpalm, Wickman, & Holmgren, 2010; Hamza & Wickman, 2008; Jakobson & Wickman, 2007; Lidar, Lundqvist, & Ostman, 2006; Lundegard & Wickman, 2007; Wickman, 2006).

Hybridization of Practices in Teacher-Researcher Collaboration.

In this paper we present experiences from a joint collaborative research project which may be described as an encounter between a school science teaching practice and a university science didactics research practice. We provide narratives which demonstrate how the encounter between these two communities of practice interacted to produce hybridization between the two in terms of mutual influences, resulting in the conceptual and practical development of both communities of practice. We argue that what happened in the project suggests one way of reducing the gap between educational research and teaching through the emergence of practices where the roles of teachers and researchers become blurred.