Flooding and hydrologic connectivity modulate community assembly in a dynamic river-floodplain ecosystem

Stefano Larsen ... [et al.]

Larsen Stefano (30%)

Karaus Ute (20%)
Claret Cecile (20%)
Šporka Ferdinand (10%)
Hamerlík Ladislav 1974- (10%) UMBFP09 - Katedra biológie a environmentálnych štúdií
Tockner Klement (10%)

PLOS ONE. Vol. 14, no. 4 (2019), pp. [1-22]. - San Francisco : Public Library of Science, 2019

ekológia - ecology

 

biológia - biology

 

ekosystémy - ecosystems

 

rieky - rivers

 

záplavy

 

hydrológia - hydrology

 

články - journal articles

angličtina

Spojené štáty

Braided river floodplains are highly dynamic ecosystems, where aquatic communities are strongly regulated by the hydrologic regime. So far, however, understanding of how flow variation influences assembly mechanisms remains limited. We collected benthic chironomids and oligochaetes over a year across a lateral connectivity gradient in the semi-natural Tagliamento River (Italy). Four bankfull flood events occurred during the study, allowing the assessment of how flooding and hydrologic connectivity mediate the balance between stochastic and deterministic community assembly. While invertebrate density and richness were positively correlated with connectivity, diversity patterns showed no significant correlation. Species turnover through time increased with decreasing connectivity. Contrary to expectations, hydrologic connectivity did not influence the response of community metrics (e.g. diversity, density) to floods. Invertebrate composition was weakly related to connectivity, but changed predictably in response to floods. Multivariate ordinations showed that faunal composition diverged across the waterbodies during stable periods, reflecting differential species sorting across the lateral gradient, but converged again after floods. Stable hydrological periods allowed communities to assemble deterministically with prevalence of non-random beta-diversity and co-occurrence patterns and larger proportion of compositional variation explained by local abiotic features. These signals of deterministic processes declined after flooding events. This occurred despite no apparent evidence of flood-induced homogenisation of habitat conditions. This study is among the first to examine the annual dynamic of aquatic assemblages across a hydrologic connectivity gradient in a natural floodplain. Results highlight how biodiversity can exhibit complex relations with hydrologic connectivity. However, appraisal of the assembly mechanisms through time indicated that flooding shifted the balance from deterministic species sorting across floodplain habitats, towards stochastic processes related to organisms redistribution and the likely resetting of assembly to earlier stages

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