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Testing for size-dependent trade-offs of clustering in Nephila clavipes

Testing for size-dependent trade-offs of clustering in Nephila clavipes. Laura Sauvage (CMC ‘14) & Haley Godtfredsen (Scripps ‘ 16). Introduction. Web ecology Prey capture Males Kleptoparasites Predation. Nephila clavipes. Large. Medium. Small.

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Testing for size-dependent trade-offs of clustering in Nephila clavipes

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  1. Testing for size-dependent trade-offs of clustering in Nephila clavipes Laura Sauvage (CMC ‘14) & Haley Godtfredsen (Scripps ‘16)

  2. Introduction Web ecology • Prey capture • Males • Kleptoparasites • Predation

  3. Nephila clavipes Large Medium Small

  4. Another component of web environment: Solitary (built alone) Clustered (attached to other webs)

  5. Theoretical costs and benefits of cluster formation: Cost = competition for food Benefit = less predation risk per spider

  6. Daniella Barraza, 2012 • Cost: Medium spiders caught more prey if solitary than clustered. - No difference for small spiders. • Benefit: Longer web tenure if clustered. - More so for medium than small spiders.

  7. Sauvage & Godtfredsen, 2013 Hypothesis: Costs & benefits of clustering will be size-dependent. Preliminary data- • Frequency of clustering • Variation in web experience based on spider size and clustering

  8. Methods • Firestone Center for Restoration Ecology • Baru, Costa Rica

  9. Initial Measurements (example data)

  10. Monitoring Data (example data)

  11. Measuring costs and benefits of cluster formation: Competition for food: prey capture rate Lower predation risk • Web duration • Leg autotomy • Web condition • Reason for disappearance

  12. Frequencies of….

  13. Frequencies of….

  14. Frequencies of….

  15. Influence of spider size on … NS = not significant + = positive correlation

  16. Influence of spider size on … Influence of clustering on …

  17. Significance • Studying the costs/benefits of living in a group (cluster) • Do these trade-offs differ with spider size?

  18. Preliminary Data Prey capture Predation Spider Size Clustering X X X

  19. To Be Determined • Do size-dependent trade-offs exist in clusters? • Frequency with which spiders of different sizes are clustered or solitary. • Cluster formation • Order of arrival • Effect of size

  20. Acknowledgements Keck Science Department Professor E. Ferree Professor D. McFarlane Greddy Arias-- Firestone Caretaker Pitzer College

  21. Preliminary Results Bigger spiders have bigger webs. n=17 Mean web diameter (mm) n=183 n=138

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