The ecological and evolutionary impacts of altered
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This document discusses the ecological and evolutionary impacts of climate change on trophic structures in aquatic communities, specifically utilizing a study of vernal pond food webs. It reveals that increased warming and drought lead to destabilized food web structures, affecting predator abundance and resulting in natural selection changes in species traits. The findings suggest that climate change not only alters community dynamics but also drives evolutionary responses through changes in predator pressures.
The ecological and evolutionary impacts of altered
- 1. The ecological and evolutionary impacts of altered trophic structure due to climate change in aquatic communities Edmund M. Hart and Nicholas J. Gotelli University of Vermont @DistribEcology
- 2. Talk outline • Background on climate change • Study system / Experimental design • How will climate change alter community structure? o How climate change destabilizes trophic structure • Using network analysis o The Evolutionary impacts of climate change in a model organism • Using a common garden experiment
- 3. Climate change Models predict changes in both temperature and precipitation
- 4. Climate change Lavergne et al 2010 Framework for understanding the impacts of climate change on species
- 5. Climate change Decreasing altitude (increasing temperature) Lavergne et al 2010 Woodward et al 2010
- 6. Climate change Chlamydomonas Lavergne et al 2010 Collins and Bell 2004
- 7. Questions 1. How will climate change alter trophic structure in a model system? 2. Will altered trophic structure be an agent of selection?
- 8. Study system
- 9. Study system
- 10. Vernal pond foodweb Detrital / bacterial food source
- 17. Food webs Question: How will climate change alter trophic structure in a model system? Hypothesis: Increased warming and drought severity will create more variable habitat that destabilizes food web structure.
- 18. Food webs Species Link ● ● ● ● ● ● ● ● Each pond has a food web for each week it was sampled. Each was characterized by two metrics links / species (L/S) and the proportion of links that are predators (P)
- 19. Food webs Web dynamics 2.0 ● ● ● ● 1.8 ● ● ● ● ● ● ● 1.6 ● ● 1.4 ● ● ● ● ● ● ● ● L/S 1.2 ● ● ● ● ● 1.0 ● ● ● ● 0.8 ● ● ● ● ● ● ● ● ● ● 0.6 ● ● ● ● ● ● ● ● ● ● 2 4 6 8 10 12 14 Study week ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.20 ● ● ● ● ● ● ● ● ● ● ● ● 0.15 ● ● ● 0.10 ● ● Pt - Pt-1 ● ● 0.05 ● ● ● ● 0.00 ● ● ● ● ● ● ● −0.05 Each pond can be characterized by ● ● ● a time series of network metrics 2 4 6 Study week 8 10 12
- 20. Food webs Web dynamics ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● How can we quantify ● ● ● ● ● the differences between ● ● ● ● ● these two time series? ● ●
- 21. Food webs Web dynamics Use autoregressive model parameters to quantify temporal stability.
- 22. Food webs Web dynamics Quantify the variance of first order difference of a time series.
- 23. Food webs Hierarchical mixed model results for L/S Enhances network stability 0.4 ● ● ● 0.2 0.0 ● ● Effect size ● ● ● −0.2 ● −0.4 0.3 0.4 0.5 0.6 0.7 0.8 Water loss rate Destabilizes network structure Ponds with a smaller water loss rate have the most temporally stable networks.
- 24. Food webs Hierarchical model of stationary variance in P 0.22 ● 0.20 Stationary SD ● ● 0.18 ● ● ● ● 0.16 ● ● 0.14 0.12 0.3 0.4 0.5 0.6 0.7 0.8 Water loss rate Ponds with a smaller water loss rate have lower variability in the proportion of links that are predators
- 25. Food webs Why are dynamics different? Less variable habitats have far fewer larval stage predators.
- 26. Food webs Predator use of stable habitat ● ● ● 2.0 ● ● ● ● ● ● ● 1.8 ● 1.6 ● ● ● ● ● 1.4 ● ● ● ● ● L/S ● ● ● ● ● 1.2 ● ● ● ● 1.0 ● ● ● ● ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● 0.6 ● ● ● ● ● 2 4 6 8 10 12 14 ● ● Study week ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Stable networks have high numbers of larval predators
- 27. Food webs Predator use of unstable habitat 2.0 ● ● ● ● ● ● ● ● ● 1.8 ● ● ● ● ● 1.6 ● ● ● ● ● ● ● ● 1.4 L/S ● ● ● ● ● 1.2 ● ● ● ● 1.0 ● ● ● ● ● ● ● ● 0.8 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 2 4 6 8 10 12 14 Study week ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Unstable networks are used transiently adult predators
- 28. Food webs Conclusions • Water loss rate had a strong effect on trophic structure dynamics. o High water loss rates decreased temporal stability o Increased the variance in the proportion of predators • Changes in dynamics most likely due to changes in larval stage habitat usage o Ponds with unstable web dynamics had few larval predators
- 29. Natural selection Question: Will altered trophic structure be an agent of selection driving evolutionary change? Hypothesis: Leuning 1992 D. pulex has demonstrated rapid microevolutionary responses to predators in laboratory studies. We expect a similar response if climate change alters trophic structure by reducing predators. Spitze 1991
- 30. Natural Selection D. pulex life cycle • Daphnia pulex D. pulex is cyclically parthenogenic producing clonal daughters
- 33. Natural selection Common garden design Mothers A B C Clones A 1 A 2 A 3 B1 B2 B3 C1 C2 C3 D. pulex were collected in September of 2010 and raised in a growth chamber for 3 months prior to the start of the experiment.
- 34. Natural selection Traits measured 1st instar D. pulex Trait Type Method Frequency Measured from Spine length Morphological Every other day photo Measured from Body length Morphological Every other day photo Measured from Total length Morphological Every other day photo 0.568 mm Measured from Head width Morphological Every other day photo Counted live born Clutch size Life-history Every occurrence young Clutch number Life-history Counted live Every occurrence Calculated from Once per 0.203 mm Growth rate Life-history photographs individual Intrinsic Calculated via life Life-history population table analysis of Once per pond growth rate (r) individuals
- 35. Natural selection Trait results Lower values of 1st instar spine length and r were selected for in the most unstable ponds
- 36. Natural selection Trait results
- 37. Natural selection Predators abundance Predator abundance was greatest in the most stable ponds and lowest in the least stable.
- 38. Natural selection Trait correlation with predator abundance R2 = 0.76 R2 = 0.69 Predator abundance was tightly correlated with each trait value. Traits were not correlated with any other covariate
- 39. Natural selection Conclusions • 1st instar tail spine length and r show a genetically based change in trait means. • More variable habitats have lower predator abundance. • Trait response is due to climate change, but mediated through that reduction in predator pressure. • Lab results from earlier selection experiments can be useful in making predictions
- 40. Bringing it all together Habitat variability gradient due to climate change Decrease in food-web stability 2.0 ● 2.0 ● ● 1.8 1.8 ● 1.6 ● 1.6 ● 1.4 ● ● ● ● ● Changes in trophic structure directly 1.4 ● L/S L/S 1.2 1.0 related to climate change cause an 1.2 1.0 ● ● ● indirect evolutionary response. 0.8 ● ● ● ● 0.8 ● 0.6 ● ● ● ● ● ● ● ● 2 4 6 8 10 12 14 2 4 6 8 10 12 14 Study week Study week Decrease in predator abundance
- 41. Acknowledgements Funding from Vermont EPSCoR and the NSF Nick Gotelli • Alison Brody • DonTobi and the Jericho Research Forest • Many undergrad field assistants through the years, especially Cyrus Mallon, Chris Graves, Rachel Brooks, Maria Donaldson,Collin Love, Erin Hayes- Pontius and Jordan Smith. Head field assistant Allie Hart (my dad) Tuesday the dog