TY - JOUR
T1 - The arrangement of resources in patchy landscapes
T2 - Effects on distribution, survival, and resource acquisition of chironomids
AU - Silver, Pamela
AU - Cooper, J. Kevin
AU - Palmer, Margaret A.
AU - Davis, Edward J.
N1 - Funding Information:
Acknowledgements This work was supported by NSF grants DEB 9319074 and 9741065 to P.S.B. and DEB 9318060 and 7941101 to M.A.P. Chironomus eggs were generously supplied by E. Greer of the U.S. Fish and Wildlife Service. Thanks to S. Stanko-Mishic and E. Billman for all the TLC they provided the midges in the culture room. Without the help of E. Davis we would not have had our landscapes or instar I larvae when we needed them. R. Baker, L. Belyea, M.G. Butler, S. Collins, B.C. Cowell, G.W. Fairchild, J. Lancaster, C. Vaughn, and several anonymous reviewers provided valuable comments on earlier versions of this paper. Special thanks to C. Osenberg whose patient but critical analysis greatly improved this paper. Contribution no. 1 from The Penn State Behrend Center for Mathematical Biology.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2000
Y1 - 2000
N2 - The spatial arrangement of resources in patchy habitats influences the distribution of individuals and their ability to acquire resources. We used Chironomus riparius, a ubiquitous aquatic insect that uses leaf particles as an important resource, to ask how the dispersion of resource patches influences the distribution and resource acquisition of mobile individuals in patchy landscapes. Two experiments were conducted in replicated laboratory landscapes (38x38 cm) created by arranging sand and leaf patches in a 5x5 grid so that the leaf patches were either aggregated or uniformly dispersed in the grid. One-day-old C. Riparius larvae were introduced into the landscapes in one of three densities (low, medium, high). In experiment 1, we sampled larvae and pupae by coring each patch in each landscape 3, 6, 12, or 24 days after adding larvae. In experiment 2, emerging adults were collected daily for 42 days from each patch in each landscape. In aggregated landscapes, individuals were aggregated in one patch type or the other during a particular developmental stage, but the 'preferred' type changed depending on developmental stage and initial density. Adult emergence was lower by about 30% in all aggregated landscapes. In dispersed landscapes, individuals used both types of patch throughout their life cycles at all initial densities. Thus, patch arrangement influences the distribution of mobile individuals in landscapes, and it influences resource acquisition even when average resource abundance is identical among landscapes. Regardless of patch arrangement, high initial density caused accumulation of early instars in edge patches, 75% mortality of early instars, a 25% increase in development time, and a 60% reduction in adult emergence. Because mortality was extremely high among early-in-star larvae in high-density treatments, we do not have direct evidence that the mechanism by which patch arrangement operates is density dependent. However, the results of our experiments strongly suggest that dispersion of resource patches across a landscape reduces local densities by making non-resource patches available for use, thereby reducing intraspecific competition.
AB - The spatial arrangement of resources in patchy habitats influences the distribution of individuals and their ability to acquire resources. We used Chironomus riparius, a ubiquitous aquatic insect that uses leaf particles as an important resource, to ask how the dispersion of resource patches influences the distribution and resource acquisition of mobile individuals in patchy landscapes. Two experiments were conducted in replicated laboratory landscapes (38x38 cm) created by arranging sand and leaf patches in a 5x5 grid so that the leaf patches were either aggregated or uniformly dispersed in the grid. One-day-old C. Riparius larvae were introduced into the landscapes in one of three densities (low, medium, high). In experiment 1, we sampled larvae and pupae by coring each patch in each landscape 3, 6, 12, or 24 days after adding larvae. In experiment 2, emerging adults were collected daily for 42 days from each patch in each landscape. In aggregated landscapes, individuals were aggregated in one patch type or the other during a particular developmental stage, but the 'preferred' type changed depending on developmental stage and initial density. Adult emergence was lower by about 30% in all aggregated landscapes. In dispersed landscapes, individuals used both types of patch throughout their life cycles at all initial densities. Thus, patch arrangement influences the distribution of mobile individuals in landscapes, and it influences resource acquisition even when average resource abundance is identical among landscapes. Regardless of patch arrangement, high initial density caused accumulation of early instars in edge patches, 75% mortality of early instars, a 25% increase in development time, and a 60% reduction in adult emergence. Because mortality was extremely high among early-in-star larvae in high-density treatments, we do not have direct evidence that the mechanism by which patch arrangement operates is density dependent. However, the results of our experiments strongly suggest that dispersion of resource patches across a landscape reduces local densities by making non-resource patches available for use, thereby reducing intraspecific competition.
UR - http://www.scopus.com/inward/record.url?scp=0033896155&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033896155&partnerID=8YFLogxK
U2 - 10.1007/s004420050009
DO - 10.1007/s004420050009
M3 - Article
AN - SCOPUS:0033896155
SN - 0029-8549
VL - 124
SP - 216
EP - 224
JO - Oecologia
JF - Oecologia
IS - 2
ER -