Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Ecology Letters 1079-1090 Biodiversity body mass coexistence competition migration neutrality niche space niche-based processes species similarity 2009 fdi:010048177 ENG Ecology Letters 1461-023X ISI:000269742600008 10 10.1111/j.1461-0248.2009.01364.x https://www.documentation.ird.fr/hor/fdi:010048177 https://www.documentation.ird.fr/intranet/publi/2009/09/010048177.pdf 12 Horizon (IRD) Ecological models suggest that high diversity can be generated by purely niche-based, purely neutral or by a mixture of niche-based and neutral ecological processes. Here, we compare the degree to which four contrasting hypotheses for coexistence, ranging from niche-based to neutral, explain species richness along a body mass niche axis. We derive predictions from these hypotheses and confront them with species body-mass patterns in a highly sampled marine phytoplankton community. We find that these patterns are consistent only with a mechanism that combines niche and neutral processes, such as the emergent neutrality mechanism. In this work, we provide the first empirical evidence that a niche-neutral model can explain niche space occupancy pattern in a natural species-rich community. We suggest this class of model may be a useful hypothesis for the generation and maintenance of species diversity in other size-structured communities. 021 ; 082 UR212