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

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Presentation on theme: "Testing for size-dependent trade- offs of clustering in Nephila clavipes Laura Sauvage (CMC ‘14) & Haley Godtfredsen (Scripps ‘16)"— Presentation transcript:

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 LargeMediumSmall

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 Spider IDSolitary/ Clustered Date Found ColorNeighbor Females Spider Size (mm) Web Size (m) 1S7/5/2013N/A S7/5/2013N/A C7/5/2013Blue C7/6/2013Green S7/6/2013N/A Initial Measurements (example data)

10 Spider ID DateWeb Condition # Prey# Legs# Neighbor Females 17/15/2013Good08N/A 27/15/2013Good28N/A 37/15/2013Poor071 47/15/2013Good081 57/15/2013Okay17N/A 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 Clustering Clustered: 191 webs (48%) Solitary: 209 webs (52%) Frequencies of….

13 ClusteringLeg Autotomy Clustered: 191 webs (48%)No: 367 webs (94%) Solitary: 209 webs (52%)Yes: 25 webs (6%) Frequencies of….

14 ClusteringLeg AutotomyWeb Fate Clustered: 191 webs (48%)No: 367 webs (94%) Moved: 160 webs (65%) Solitary: 209 webs (52%)Yes: 25 webs (6%) Depredated: 86 webs (35%) Frequencies of….

15 ClusteringPrey Capture Leg Autotomy Spider/Web Fate Spider Size NS + Influence of spider size on … NS = not significant + = positive correlation

16 ClusteringPrey Capture Leg Autotomy Spider/Web Fate Spider Size NS + Influence of spider size on … Influence of clustering on … Prey Capture Leg Autotomy Spider/Web Fate Clustered compared to Solitary NS

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

18 Prey capture Preliminary Data 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 Mean web diameter (mm) Bigger spiders have bigger webs. n=17 n=183 n=138


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