Herbivores differentially limit the seedling growth and sapling recruitment of two dominant rain forest trees

Resource heterogeneity may influence how plants are attacked and respond to consumers in multiple ways. Perhaps a better understanding of how this interaction might limit sapling recruitment in tree populations may be achieved by examining species’ functional responses to herbivores on a continuum of resource availability. Here, we experimentally reduced herbivore pressure on newly established seedlings of two dominant masting trees in 40 canopy gaps, across c. 80 ha of tropical rain forest in central Africa (Korup, Cameroon). Mesh cages were built to protect individual seedlings, and their leaf production and changes in height were followed for 22 months. With more light, herbivores increasingly prevented the less shade-tolerant Microberlinia bisulcata from growing as tall as it could and producing more leaves, indicating an undercompensation. The more shade-tolerant Tetraberlinia bifoliolata was much less affected by herbivores, showing instead near to full compensation for leaf numbers, and a negligible to weak impact of herbivores on its height growth. A stage-matrix model that compared control and caged populations lent evidence for a stronger impact of herbivores on the long-term population dynamics of M. bisulcata than T. bifoliolata. Our results suggest that insect herbivores can contribute to the local coexistence of two abundant tree species at Korup by disproportionately suppressing sapling recruitment of the faster-growing dominant via undercompensation across the light gradient created by canopy disturbances. The functional patterns we have documented here are consistent with current theory, and, because gap formations are integral to forest regeneration, they may be more widely applicable in other tropical forest communities. If so, the interaction between life-history and herbivore impact across light gradients may play a substantial role in tree species coexistence.

Effects of overt self-­talk on team partners’ other-efficacy and performance in a golf putting task

Introduction According to Lent and Lopez’ (2002) tripartite view of efficacy beliefs, members of a team form beliefs about the efficacy of their team partners. This other-efficacy belief can influence individual performance as shown by Dunlop, Beatty, and Beauchamp (2011) in their experimental study using manipulated performance feedback to alter other-efficacy beliefs. Participants holding favorable other-efficacy beliefs outperformed those with lower other--‐efficacy beliefs. Antecedents of such other-efficacy beliefs are amongst others perceptions regarding motivation and psychological factors of the partner (Jackson, Knapp, & Beauchamp, 2008). Overt self-talk could be interpreted as the manifestation of such motivational or psychological factors. In line with this assumption, in an experimental study using dubbed videos of the same segment of a tennis match, Van Raalte, Brewer, Cornelius, and Petitpas (2006) found that players were perceived more favorably (e.g., more concentrated, and of higher ability levels) when shown with dubbed positive self-talk as compared to dubbed negative or no dubbed self--‐talk. Objectives The aim of the study was to examine the possible effects of a confederate’s overt self-talk on participants’ other-efficacy beliefs and performance in a team setting. Method In a laboratory experiment (between-subjects, pre-post-test design, matched by pretest performance) 89 undergraduate students (female = 35, M = 20.81 years, SD = 2.34) participated in a golf putting task together with a confederate (same gender groups). Depending on the experimental condition (positive, negative, or no self-talk), the confederate commented his or her putts according to a self-talk script. Bogus performance feedback assured that the performance of the confederate was held constant. Performance was measured as the distance to the center of the target, other-efficacy by a questionnaire. Results The data collection has just finished and the results of repeated measures analyses of variance will be presented and discussed at the congress. We expect to find higher other-efficacy beliefs and better individual performance in the positive self-talk condition. References Dunlop, W.L., Beatty, D.J., & Beauchamp, M.R. (2011). Examining the influence of other-efficacy and self-efficacy on personal performance. Journal of Sport & Exercise Psychology, 33, 586-593. Jackson, B., Knapp, P., & Beauchamp, M.R. (2008). Origins and consequences of tripartite efficacy beliefs within elite athlete dyads. Journal of Sport and Exercise Psychology, 30, 512-540. Lent, R.W., & Lopez, F.G. (2002). Cognitive ties that bind: A tripartite view of efficacy beliefs in growth--‐promoting relationships. Journal of Social and Clinical Psychology, 21, 256-286. Van Raalte, J.L., Brewer, B.W, Cornelius, A.E., & Petitpas, A.J. (2006). Self-presentational effects of self-talk on perceptions of tennis players. Hellenic Journal of Psychology, 3, 134-149.