Species alliances and hidden niche dimensions drive species clustering along a hydric gradient in a semiarid grassland

• Published in: Ecology letters Vol. 25; no. 12; pp. 2651 - 2662
• Main Authors: Martínez‐Blancas, Alejandra, Belaustegui, Ian Xul, Martorell, Carlos
• Format: Journal Article
• Language: English
• Published: Paris Blackwell Publishing Ltd 01.12.2022
• Subjects: Clustering; Coexistence; Competition; emergent neutrality; environmental gradients; Grasslands; hidden niches; hydric stress; indirect facilitation; indirect interactions; Interspecific relationships; Niches; Species; species clumping; species interactions
• ISSN: 1461-023X; 1461-0248
• DOI: 10.1111/ele.14122

Clustering of species with similar niches or traits occurs in communities, but the mechanisms behind this pattern are still unclear. In the emergent neutrality model, species with similar niches and competitive ability self‐organise into clusters. In the hidden‐niche model, unaccounted‐for niche differences stabilise coexistence within clusters. Finally, clustering may occur through alliances of species that facilitate each other. We tested these hypotheses using population‐growth models that consider interspecific interactions parameterised for 35 species using field data. We simulated the expected community dynamics under different species‐interaction scenarios. Interspecific competition was weaker within rather than between clusters, suggesting that differences in unmeasured niche axes stabilise coexistence within clusters. Direct facilitation did not drive clustering. In contrast, indirect facilitation seemingly promoted species alliances in clusters whose members suppressed common competitors in other clusters. Such alliances have been overlooked in the literature on clustering, but may arise easily when within cluster competition is weak. Clustering of species with similar niches or traits occurs in communities, but the mechanisms behind this pattern are still unclear. We found species clusters over a hydrological niche axis. These clusters comprise species that differ in other niche axes and that jointly constrain their common competitors.