Do constrained immigration rates and high beta diversity explain contrasting productivity-diversity patterns measured at different scales?

Connolly, Niall M., and Pearson, Richard G. (2020) Do constrained immigration rates and high beta diversity explain contrasting productivity-diversity patterns measured at different scales? Oecologia, 194 (3). pp. 481-490.

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The relationship between productivity and diversity is controversial because of disparity between unimodal and monotonic patterns, especially when occurring simultaneously at different scales. We used stream-side artificial channels to investigate how the availability of a major resource (leaf litter) affected stream invertebrate abundance and diversity at leaf-pack and whole-channel scales. At the larger scale, invertebrate diversity increased monotonically with increasing litter resource density, whereas at the smaller scale the relationship was hump-shaped, in keeping with reports in the literature. This divergence at higher resource levels suggests that multiple mechanisms may be operating. Our results indicate that consistently high species turnover (beta diversity) caused the monotonic pattern because of a species-area or "sampling effect" in which new species accumulate with increasing number of samples. The hump-shaped pattern was due to constrained immigration because of a "dilution effect" in which a limited number of immigrants is spread out among the increasing number of available patches. We propose that the relationship between productivity or resource availability and alpha diversity is generally hump-shaped and the scale-dependent contrast in the relationship only arises where the species pool is large and beta diversity is high. Differences in beta diversity may, therefore, explain some of the contrasting patterns in the productivity-diversity relationship previously reported.We suggest that continuing immigration by rare taxa is important in sustaining species diversity when productivity is high. The hump-shaped pattern has implications for the impact of anthropogenic ecosystem enrichment on species diversity.

Item ID: 64661
Item Type: Article (Research - C1)
ISSN: 1432-1939
Keywords: Sampling effect, Dilution effect, Monotonic pattern, Humped pattern, Stream assemblage
Copyright Information: © Springer-Verlag GmbH Germany, part of Springer Nature 2020.
Funders: Cooperative Research Centre for Tropical Rainforest Ecology and Management, James Cook University (JCU)
Date Deposited: 21 Oct 2020 07:30
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310304 Freshwater ecology @ 100%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1803 Fresh, ground and surface water systems and management > 180303 Fresh, ground and surface water biodiversity @ 100%
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