In tropical forests, selective logging removes large trees that are often the main contributors to pollination. We studied pollination patterns of the African mahogany, Entandrophragma cylindricum (Sapelli). We investigated two plots in Cameroon corresponding to three tree densities: unlogged forest (Ndama 2002), a mildly logged forest 1 year after logging (Ndama 2003) and a severely logged forest 30 years after logging (Dimako). We used four microsatellite markers to perform paternity analysis. Selfing remained below 2% in all treatments. Pollen flow was mainly long distance but with some proximity effects. Average observed within-plot pollination distances were 338, 266 and 385 m, and pollination by trees outside the plots was 70% (Ndama 2002), 74% (Ndama 2003) and 66% (Dimako). Despite sampling a limited number of seeds from a limited number of mother trees, we obtained seeds sired by 35.6-38.3% of the potential within-plot pollen donors. While trees 20 cm in diameter contributed to pollination, results in Dimako suggest that individual larger trees contribute more to pollination than small ones. This effect was not detected in the other treatments. The results suggest extensive pollen flow in Sapelli. Hence, in Sapelli, the main limiting factor for regeneration after logging may be a reduction in the number of trees capable of producing seeds rather genetic effects due to limits to pollen dispersal.

The idea that tropical forest and savanna are alternative states is crucial to how we manage these biomes and predict their future under global change. Large-scale empirical evidence for alternative stable states is limited, however, and comes mostly from the multimodal distribution of structural aspects of vegetation. These approaches have been criticized, as structure alone cannot separate out wetter savannas from drier forests for example, and there are also technical challenges to mapping vegetation structure in unbiased ways. Here, we develop an alternative approach to delimit the climatic envelope of the two biomes in Africa using tree species lists gathered for a large number of forest and savanna sites distributed across the continent. Our analyses confirm extensive climatic overlap of forest and savanna, supporting the alternative stable states hypothesis for Africa, and this result is corroborated by paleoecological evidence. Further, we find the two biomes to have highly divergent tree species compositions and to represent alternative compositional states. This allowed us to classify tree species as forest vs. savanna specialists, with some generalist species that span both biomes. In conjunction with georeferenced herbarium records, we mapped the forest and savanna distributions across Africa and quantified their environmental limits, which are primarily related to precipitation and seasonality, with a secondary contribution of fire. These results are important for the ongoing efforts to restore African ecosystems, which depend on accurate biome maps to set appropriate targets for the restored states but also provide empirical evidence for broad-scale bistability.

ABSTRACT. In 2014, the Third International Conference on the resilience of social-ecological systems chose the theme "resilience and development: mobilizing for transformation." The conference aimed specifically at fostering an encounter between the experiences and thinking focused on the issue of resilience through a social and ecological system perspective, and the experiences focused on the issue of resilience through a development perspective. In this perspectives piece, we reflect on the outcomes of the meeting and document the differences and similarities between the two perspectives as discussed during the conference, and identify bridging questions designed to guide future interactions. After the conference, we read the documents (abstracts, PowerPoints) that were prepared and left in the conference database by the participants (about 600 contributions), and searched the web for associated items, such as videos, blogs, and tweets from the conference participants. All of these documents were assessed through one lens: what do they say about resilience and development? Once the perspectives were established, we examined different themes that were significantly addressed during the conference. Our analysis paves the way for new collective developments on a set of issues: (1) Who declares/assign/cares for the resilience of what, of whom? (2) What are the models of transformations and how do they combine the respective role of agency and structure? (3) What are the combinations of measurement and assessment processes? (4) At what scale should resilience be studied? Social transformations and scientific approaches are coconstructed. For the last decades, development has been conceived as a modernization process supported by scientific rationality and technical expertise. The definition of a new perspective on development goes with a negotiation on a new scientific approach. Resilience is presently at the center of this negotiation on a new science for development.