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Size-Dependent Trade-Offs in Nephila Clavipes Clustering

Explore how spider size influences benefits and costs of living in clusters vs. solitary webs. Preliminary results show larger spiders have larger webs. Study conducted by Laura Sauvage (CMC ‘14) & Haley Godtfredsen (Scripps ‘16) in web ecology.

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Size-Dependent Trade-Offs in Nephila Clavipes Clustering

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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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