Slide 1

The Impact of Variable Precipitation on Vernal Pond Community Structure and Population Dynamics Ted Hart, Gotelli Lab Slide 2 Overview Background Climate change effects Vernal ponds Methods Experimental design Modeling methods Results Conclusions Future research directions Slide 3 Climate change Slide 4 Slide 5 Vernal Pond Drying Slide 6 Vernal Pond Communities Slide 7 Mean and Variance Mean Water Level Water level Variance Slide 8 Study question How do changes in mean water level and water level variability caused by climate change affect vernal pond invertebrate communities? Slide 9 Overview Background Climate change effects Vernal ponds Methods Experimental design Modeling methods Results Conclusions Future research directions Slide 10 Study Location UVM Jericho Research Forest, Jericho, VT Slide 11 Field Methods The experimental unit 100 (cm) 50 (cm) 34 (cm) Slide 12 Field Methods Surface response design using two variables, mean water level and water level variability. Surface response 7 Levels of Water Variation 7 Levels of Water Fully crossed for 49 tubs Means (cm): 6.6,9.9,13.2, 16.5,19.8, 23.1, 26.4 Coeffecients of Variation (C.V.): 0,.1,.2,.3,.4,.5,.6 ~1.5 m Slide 13 Field Methods Treatments C.V. = Slide 14 Laying out tubs Slide 15 Filling and Seeding Slide 16 The final layout Slide 17 Sampling and filling Slide 18 Pumping a full tub Slide 19 Destruction! Slide 20 Slide 21 Modeling Methods Recall from Bcor 12 some simple population models ExponentialLogistic Slide 22 Modeling Methods Discrete time form Natural log Im non-linear and I taste bad! Regression is easy with me! Slide 23 Modeling Methods Estimated from time series models using Bayesian state-space model Growth rate Density dependence Population variability K (population size) Estimated from destructive sampling Abundance or presence/absence Species Richness PIE Slide 24 Modeling Methods Four candidate models developed based on treatments Slide 25 Modeling Methods Four candidate models developed based on treatments Slide 26 Modeling Methods Models fit using Bayesian regression in R with package MCMCPack 0.9-4 and coda 0.13-1 Best fitting models selected using Bayes Factor Values >1 indicate support for Model 1 Slide 27 Overview Background Climate change effects Vernal ponds Methods Experimental design Modeling methods Results Conclusions Future research directions Slide 28 Results Time-Series Sampling Chironomidae Chaoboridae Culicidae Slide 29 Results Time-Series Sampling Chironomidae Slide 30 Results Time-Series Sampling Chironomidae Slide 31 Results Time-Series Sampling Chironomidae Slide 32 Results Time-Series Sampling Chironomidae Slide 33 Results Time-Series Sampling Chaoboridae Slide 34 Results Time-Series Sampling Chaoboridae Slide 35 Results Time-Series Sampling Chaoboridae Slide 36 Results Time-Series Sampling Chaoboridae Slide 37 Results Time-Series Sampling Culicidae Slide 38 Results Time-Series Sampling Culicidae Slide 39 Results Time-Series Sampling Culicidae Slide 40 Results Destructive Sampling Slide 41 Overview Background Climate change effects Vernal ponds Methods Experimental design Modeling methods Results Conclusions Future research directions Slide 42 What does it all mean? Climate change predictions will alter the mean and variance of water levels in vernal ponds. Taxa respond differently to the same climate variable, changes in mean water level. Changes in population size Changes in density dependence Variance within a pond had only a marginal effect. Community metrics didnt show any response. Slide 43 Thanks! Committee members Nick, Alison, Sara and Brian Undergrad Helpers Cyrus, Chris, Autumn and Erin