Local and regional processes determine plant species richness in a river-network metacommunity
2015 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 96, no 2, 381-391 p.Article in journal (Refereed) Published
River systems form dendritic ecological networks that influence the spatial structure of riverine communities. Few empirical studies have evaluated how regional, dispersal-related processes and local habitat factors interact to govern network patterns of species composition. We explore such interactions in a boreal watershed and show that riparian plant species richness increases strongly with drainage size, i.e., with downstream position in the network. Assemblage composition was nested, with new species successively added downstream. These spatial patterns in species composition were related to a combination of local and regional processes. Breadth in local habitat conditions increased downstream in the network, resulting in higher habitat heterogeneity and reduced niche overlap among species, which together with similar trends in disturbance, allows more species to coexist. Riparian edaphic conditions were also increasingly favorable to more species within the regional pool along larger streams, with greater nitrogen availability (manifested as lower C:N) and more rapid mineralization of C and N (as indicated by ratios of stable isotopes) observed with downstream position in the network. The number of species with capacity for water dispersal increased with stream size providing a mechanistic link between plant traits and the downstream accumulation of species as more propagules arrive from upstream sites. Similarity in species composition between sites was related to both geographical and environmental distance. Our results provide the first empirical evidence that position in the river network drives spatial patterns in riparian plant diversity and composition by the joint influence of local (disturbance, habitat conditions, and breadth) and regional (dispersal) forces.
Place, publisher, year, edition, pages
2015. Vol. 96, no 2, 381-391 p.
boreal, connectivity, dispersal, disturbance, hydrochory, riparian, river network, soil conditions, spatial organization, vascular plants
Environmental Sciences Ecology
Research subject biology, Environmental Science; Ecological Botany
IdentifiersURN: urn:nbn:se:umu:diva-100211DOI: 10.1890/14-0552.1ISI: 000350484600010OAI: oai:DiVA.org:umu-100211DiVA: diva2:790777
FunderSwedish Research Council Formas