Abstract
Context
The habitat amount hypothesis (HAH) posits that local species richness is driven more by the amount of habitat in the surrounding landscape than by local patch size or habitat configuration. Habitat amount and configuration influence patch attributes, however, making it difficult to isolate these relative effects on local richness.
Objectives
We tested the HAH in an experimental system in which the amount (10–80%) and configuration (clumped vs. fragmented) of habitat (red clover) were adjusted independently within individual ‘landscapes’ (256-m2 plots).
Methods
We used generalized linear models and model-selection criteria to evaluate how arthropod richness at two local scales (1 m2 and 4 m2) varied as a function of the amount or fragmentation of habitat and of the size or shape of the local patch.
Results
Local richness was largely independent of the amount or configuration of habitat, as well as patch size or shape. Local richness was best modeled as a constant for all surveys but the first, in which fragmentation alone best explained variation in species richness, followed by patch shape (which is an indirect effect of fragmentation). Habitat amount had an overwhelmingly positive effect on arthropod richness at the landscape scale, however.
Conclusions
The HAH was not supported in this experimental system: local richness was generally unaffected by the amount of habitat in the surrounding landscape, whereas habitat configuration was sometimes important. Given that habitat amount affected landscape-wide richness, it may be that the HAH only applies at the ‘landscape scale’, at least in this system.
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Code availability
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Acknowledgements
We appreciate the thoughtful comments and suggestions provided by two anonymous reviewers of the manuscript. We owe an enormous debt of gratitude to Daniel M. Pavuk, who assisted with establishing and maintaining this experimental system and conducted the arthropod surveys. This paper stems from a partnership between Kansas State University and the University-Level Research Mentorship Program at Manhattan High School. We therefore thank Janet Hanson at MHS for initiating this program and helping to connect high school seniors with prospective university research mentors.
Funding
This research was initially supported by a grant from the National Science Foundation (Grant No. DEB-9610159).
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Both authors contributed to the conceptualization and design of the analysis. Data abstraction and entry were performed by ARP, the code was written by KAW, and both authors conducted the analyses. The manuscript was written by KAW and ARP read and approved the manuscript.
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With, K.A., Payne, A.R. An experimental test of the habitat amount hypothesis reveals little effect of habitat area but transient or indirect effects of fragmentation on local species richness. Landscape Ecol 36, 2505–2517 (2021). https://doi.org/10.1007/s10980-021-01289-5
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DOI: https://doi.org/10.1007/s10980-021-01289-5