Community assembly in Lake Tanganyika cichlid fish: quantifying the contributions of both niche‐based and neutral processes

Abstract

The cichlid family features some of the most spectacular examples of adaptive radiation. Evolutionary studies have highlighted the importance of both trophic adaptation and sexual selection in cichlid speciation. However, it is poorly understood what processes drive the composition and diversity of local cichlid species assemblages on relatively short, ecological timescales. Here, we investigate the relative importance of niche‐based and neutral processes in determining the composition and diversity of cichlid communities inhabiting various environmental conditions in the littoral zone of Lake Tanganyika, Zambia. We collected data on cichlid abundance, morphometrics, and local environments. We analyzed relationships between mean trait values, community composition, and environmental variation, and used a recently developed modeling technique (STEPCAM) to estimate the contributions of niche‐based and neutral processes to community assembly. Contrary to our expectations, our results show that stochastic processes, and not niche‐based processes, were responsible for the majority of cichlid community assembly. We also found that the relative importance of niche‐based and neutral processes was constant across environments. However, we found significant relationships between environmental variation, community trait means, and community composition. These relationships were caused by niche‐based processes, as they disappeared in simulated, purely neutrally assembled communities. Importantly, these results can potentially reconcile seemingly contrasting findings in the literature about the importance of either niche‐based or neutral‐based processes in community assembly, as we show that significant trait relationships can already be found in nearly (but not completely) neutrally assembled communities; that is, even a small deviation from neutrality can have major effects on community patterns.

On the relative importance of space and environment in farmland bird community assembly

“…But beyond only a preference in habitat type, these three groups tend also to associate species sharing specific traits. Many other studies have also highlighted the relevance of using species traits to explain community assembly patterns [ 54 , 55 ]. Most of the existing literature concern aquatic organisms and tend to show that ecological determinism, and especially the relative influence of environment compared to dispersal, increases with dispersal ability and body size of the organisms under study [ 56 – 59 ].…”

“…In such highly unpredictable and changing landscapes, dispersal seems more important to deal with uncertainty, but can be not sufficient and result in ecological traps as suggested by some previous studies [ 69 , 70 ]. But, more generally, high stochasticity seems more the rule than the exception, a phenomena that also applies to more natural ecosystems [ 54 , 55 ]. This high unexplained variation may also partly result of imperfect detection.…”

Morphological and genetic correlates in the left–right asymmetric scale-eating cichlid fish of Lake Tanganyika

“…Shaded area represents the 96% confidence interval. Muschick, Indermaur & Salzburger, 2012;Janzen et al, 2017). These between-species comparative studies revealed that environmental and ecological differences play a key role in generating morphological diversity and barriers to gene flow potentially attributable to divergent selection, and it might be also the case for P. microlepis within-species populations.…”

Factors that affect the assembly of ground-dwelling beetles at small scales in primary mixed broadleaved-Korean pine forests in north-east China

“…Increasingly, a consensus was formed that both nicheand neutral-processes contribute to community assembly simultaneously (Furniss et al, 2017;Rael et al, 2018). Recently, the debate is focused on which processes (i.e., environmental and spatial processes) are more powerful and how they operate simultaneously (Janzen et al, 2017;Saravia and Momo, 2017).…”