Stochastic processes dominate community assembly in cichlid communities in Lake Tanganyika

23 The African Great Lakes are characterized by an extraordinary diversity of endemic cichlid 24 fish species. The cause of this diversity is still largely unknown. Most studies have tried to 25 solve this question by focusing on macro-evolutionary processes, such as speciation. 26 However, the ecological processes determining local cichlid diversity have so far been 27 understudied, even though knowledge on these might be crucial for understanding larger scale 28 biodiversity patterns. 29 Using trait, environmental and abundance data of cichlid fishes along 36 transects, we have 30 studied how differences in local environmental conditions influence cichlid community 31 assembly in the littoral of Lake Tanganyika, Zambia. We investigated changes in average trait 32 values and in trait-based community assembly processes along three key environmental 33 gradients. 34 Species diversity and local abundance decreased with increasing sand cover and diet35 associated traits change with depth. Analyses on within-community trait diversity patterns 36 indicated that cichlid community assembly was mainly driven by stochastic processes, to a 37 smaller extent by processes that limit the similarity among co-existing species and least by 38 filtering processes that limit the range of species traits occuring in an environment. However, 39 the dominance of these different community assembly processes did not change with 40 environmental conditions. 41 Our results suggest that local environmental conditions determine cichlid abundance, while 42 the predominance of stochastic community assembly across all environments explains why 43 the communities with the highest abundances contain most species. 44 45 not peer-reviewed) is the author/funder. All rights reserved. No reuse allowed without permission. The copyright holder for this preprint (which was . http://dx.doi.org/10.1101/039503 doi: bioRxiv preprint first posted online Feb. 12, 2016;