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Patchiness in resource distribution mitigates habitat loss: insights from high-shore grazers

Patchiness in resource distribution mitigates habitat loss: insights from high-shore grazers
Patchiness in resource distribution mitigates habitat loss: insights from high-shore grazers
Theory predicts that coarse-grained heterogeneity in the spatial distribution of resources benefits the abundances of exploiter populations that are vulnerable to habitat loss, in contrast to fine-grained habitat fragmentation. This generic principle has never been tested empirically, despite its potential application across scales of exploitation from foraging ranges to metapopulations. We designed a field experiment to measure population responses to the distributional pattern of limiting resources independently of resource richness. Populations of the rocky-shore snail Melarhaphe neritoides were monitored for responses in density to controlled manipulations of the pattern and abundance of refuges. On two shores, one with naturally high snail density and one with naturally low density, snail refuges were made by drilling holes into each of three 0.5-m2 plots in each of two categories of distribution pattern: patchy or even, at each of four richness levels: 4, 16, 36, or 64 holes per plot. We found that snail densities over the subsequent 2 yrs remained higher in patchy than even plots at the low-density shore, and higher in even than patchy plots at the high-density shore. Grazed areas were larger in patchy than even plots at low refuge richness, switching to larger in even than in patchy at high refuge richness. Both scales of pattern-by-richness interaction were explained by density-dependent overlap of foraging ranges around refuges. The novel implication for wildlife management is that vulnerable populations (often species of conservation concern) may benefit from clumping their resources, whereas robust populations (often pest species) may benefit from even distributions

extinction threshold, food-refuge interaction, fragmented landscape, habitat fragmentation, minimum viable metapopulation, resource dispersion
2150-8925
art60-[17pp]
Skov, Martin W.
cd88f083-d45d-4f18-a306-4011ca11b40b
Hawkins, Stephen J.
758fe1c1-30cd-4ed1-bb65-2471dc7c11fa
Volkelt-Igoe, Megan
3b00d0fa-141b-4821-a4ca-8df82bcff8fa
Pike, James
19172e07-5f72-4ad3-a065-a9d72703807e
Thompson, Richard C.
f439ea56-b6dd-48cf-8adb-d9c2ecc6e24d
Doncaster, C. Patrick
0eff2f42-fa0a-4e35-b6ac-475ad3482047
Skov, Martin W.
cd88f083-d45d-4f18-a306-4011ca11b40b
Hawkins, Stephen J.
758fe1c1-30cd-4ed1-bb65-2471dc7c11fa
Volkelt-Igoe, Megan
3b00d0fa-141b-4821-a4ca-8df82bcff8fa
Pike, James
19172e07-5f72-4ad3-a065-a9d72703807e
Thompson, Richard C.
f439ea56-b6dd-48cf-8adb-d9c2ecc6e24d
Doncaster, C. Patrick
0eff2f42-fa0a-4e35-b6ac-475ad3482047

Skov, Martin W., Hawkins, Stephen J., Volkelt-Igoe, Megan, Pike, James, Thompson, Richard C. and Doncaster, C. Patrick (2011) Patchiness in resource distribution mitigates habitat loss: insights from high-shore grazers. Ecosphere, 2 (5), art60-[17pp]. (doi:10.1890/ES11-00017.1).

Record type: Article

Abstract

Theory predicts that coarse-grained heterogeneity in the spatial distribution of resources benefits the abundances of exploiter populations that are vulnerable to habitat loss, in contrast to fine-grained habitat fragmentation. This generic principle has never been tested empirically, despite its potential application across scales of exploitation from foraging ranges to metapopulations. We designed a field experiment to measure population responses to the distributional pattern of limiting resources independently of resource richness. Populations of the rocky-shore snail Melarhaphe neritoides were monitored for responses in density to controlled manipulations of the pattern and abundance of refuges. On two shores, one with naturally high snail density and one with naturally low density, snail refuges were made by drilling holes into each of three 0.5-m2 plots in each of two categories of distribution pattern: patchy or even, at each of four richness levels: 4, 16, 36, or 64 holes per plot. We found that snail densities over the subsequent 2 yrs remained higher in patchy than even plots at the low-density shore, and higher in even than patchy plots at the high-density shore. Grazed areas were larger in patchy than even plots at low refuge richness, switching to larger in even than in patchy at high refuge richness. Both scales of pattern-by-richness interaction were explained by density-dependent overlap of foraging ranges around refuges. The novel implication for wildlife management is that vulnerable populations (often species of conservation concern) may benefit from clumping their resources, whereas robust populations (often pest species) may benefit from even distributions

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Published date: May 2011
Keywords: extinction threshold, food-refuge interaction, fragmented landscape, habitat fragmentation, minimum viable metapopulation, resource dispersion

Identifiers

Local EPrints ID: 189639
URI: http://eprints.soton.ac.uk/id/eprint/189639
ISSN: 2150-8925
PURE UUID: a39daf22-ca9b-4724-8916-d842102a6bf4
ORCID for C. Patrick Doncaster: ORCID iD orcid.org/0000-0001-9406-0693

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Date deposited: 06 Jun 2011 07:36
Last modified: 20 Jul 2019 01:18

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