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Survival benefits select for group living in a social spider despite reproductive costs

Bilde, T.; Coates, K.S.; Birkhofer, Klaus LU ; Bird, T.; Maklakov, Alexei A.; Lubin, Y. and Avilés, L. (2007) In Journal of Evolutionary Biology 20(6). p.2412-2426
Abstract
The evolution of cooperation requires benefits of group living to exceed costs. Hence, some components of fitness are expected to increase with increasing group size, whereas others may decrease because of competition among group members. The social spiders provide an excellent system to investigate the costs and benefits of group living: they occur in groups of various sizes and individuals are relatively short-lived, therefore life history traits and Lifetime Reproductive Success (LRS) can be estimated as a function of group size. Sociality in spiders has originated repeatedly in phylogenetically distant families and appears to be accompanied by a transition to a system of continuous intra-colony mating and extreme inbreeding. The... (More)
The evolution of cooperation requires benefits of group living to exceed costs. Hence, some components of fitness are expected to increase with increasing group size, whereas others may decrease because of competition among group members. The social spiders provide an excellent system to investigate the costs and benefits of group living: they occur in groups of various sizes and individuals are relatively short-lived, therefore life history traits and Lifetime Reproductive Success (LRS) can be estimated as a function of group size. Sociality in spiders has originated repeatedly in phylogenetically distant families and appears to be accompanied by a transition to a system of continuous intra-colony mating and extreme inbreeding. The benefits of group living in such systems should therefore be substantial. We investigated the effect of group size on fitness components of reproduction and survival in the social spider Stegodyphus dumicola in two populations in Namibia. In both populations, the major benefit of group living was improved survival of colonies and late-instar juveniles with increasing colony size. By contrast, female fecundity, female body size and early juvenile survival decreased with increasing group size. Mean individual fitness, estimated as LRS and calculated from five components of reproduction and survival, was maximized for intermediate- to large-sized colonies. Group living in these spiders thus entails a net reproductive cost, presumably because of an increase in intra-colony competition with group size. This cost is traded off against survival benefits at the colony level, which appear to be the major factor favouring group living. In the field, many colonies occur at smaller size than expected from the fitness curve, suggesting ecological or life history constraints on colony persistence which results in a transient population of relatively small colonies. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Stegodyphus dumicola, social spiders, multilevel selection, lifetime reproductive success, fitness components, cooperation
in
Journal of Evolutionary Biology
volume
20
issue
6
pages
2412 - 2426
publisher
John Wiley & Sons
external identifiers
  • scopus:35448944486
ISSN
1420-9101
DOI
10.1111/j.1420-9101.2007.01407.x
language
English
LU publication?
yes
id
57367235-51e6-45b4-bd97-01f73c254ae2 (old id 2440505)
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http://www.scopus.com/inward/record.url?eid=2-s2.0-35448944486&partnerID=40&md5=1a1fc731ecf462e9e4fc933ae478f7c8
date added to LUP
2012-06-20 11:23:42
date last changed
2017-11-12 03:24:56
@article{57367235-51e6-45b4-bd97-01f73c254ae2,
  abstract     = {The evolution of cooperation requires benefits of group living to exceed costs. Hence, some components of fitness are expected to increase with increasing group size, whereas others may decrease because of competition among group members. The social spiders provide an excellent system to investigate the costs and benefits of group living: they occur in groups of various sizes and individuals are relatively short-lived, therefore life history traits and Lifetime Reproductive Success (LRS) can be estimated as a function of group size. Sociality in spiders has originated repeatedly in phylogenetically distant families and appears to be accompanied by a transition to a system of continuous intra-colony mating and extreme inbreeding. The benefits of group living in such systems should therefore be substantial. We investigated the effect of group size on fitness components of reproduction and survival in the social spider Stegodyphus dumicola in two populations in Namibia. In both populations, the major benefit of group living was improved survival of colonies and late-instar juveniles with increasing colony size. By contrast, female fecundity, female body size and early juvenile survival decreased with increasing group size. Mean individual fitness, estimated as LRS and calculated from five components of reproduction and survival, was maximized for intermediate- to large-sized colonies. Group living in these spiders thus entails a net reproductive cost, presumably because of an increase in intra-colony competition with group size. This cost is traded off against survival benefits at the colony level, which appear to be the major factor favouring group living. In the field, many colonies occur at smaller size than expected from the fitness curve, suggesting ecological or life history constraints on colony persistence which results in a transient population of relatively small colonies.},
  author       = {Bilde, T. and Coates, K.S. and Birkhofer, Klaus and Bird, T. and Maklakov, Alexei A. and Lubin, Y. and Avilés, L.},
  issn         = {1420-9101},
  keyword      = {Stegodyphus dumicola,social spiders,multilevel selection,lifetime reproductive success,fitness components,cooperation},
  language     = {eng},
  number       = {6},
  pages        = {2412--2426},
  publisher    = {John Wiley & Sons},
  series       = {Journal of Evolutionary Biology},
  title        = {Survival benefits select for group living in a social spider despite reproductive costs},
  url          = {http://dx.doi.org/10.1111/j.1420-9101.2007.01407.x},
  volume       = {20},
  year         = {2007},
}