1. Context dependent pollinator limitation Carol C. Horvitz 1, Johan Ehrlén 2 and David Matlaga 1 1 University of Miami, Coral Gables, FL 33124 USA 2 Stockholm University, SE-106 91 Stockholm, SWEDEN Evolutionary Ecology of Multispecific Interactions in Changing Environments ATBC 2007, Morelia, Michoacan, MEXICO

2. Issue Supplemental pollination = higher plant fitness?

3. Contexts Demographic, biotic, abiotic variability in the environment Ecological, evolutionary and conservation consequences of pollen limitation e.g. Ashman et al. 2004

4. Candidate currencies for measuring fitness oFitness components oReproduction oSurvival oGrowth oPopulation growth rate oStochastic growth rate

5. Demographic transitions and fitness in a constant world o N(t+1) = A N(t) o A is a population projection matrix o Transitions and contributions between stages, a ij = fitness components o λ = population growth rate

6. o N(t+1) = X(t) N(t) o X(t) is a random variable A 1, A 2, A 3 …A K, K environmental states o Transitions and contributions in each environment, a ijβ o λ S = stochastic growth rate Tuljapurkar 1982, 1990 Demographic transitions and fitness in a variable world

7. In a variable world: sequences, frequencies and new sensitivities o Environmental dynamics o sequences along sample paths o an expected long run stationary distribution o λ s is sensitive to perturbations of means, variances, and transitions in particular environmental states o E δ, E μ, E β and others… o Tuljapurkar et al. 2003 Am Nat o Horvitz et al. 2005 Ecology

8. Lathyrus vernus Long lived perennial forest herb Ranges from central and northern Europe to Siberia Particularly well- studied example http://caliban.mpiz-koeln.mpg.de/~stueber/thome/band3/tafel_135_small.jpg

9. not exactly tropical… Tullgarnsnäset SW of Stockholm 58º6’ N, 17º4’ E Deciduous forest Quercus, Fraxinus, Betula Quercus, Fraxinus, Betula

10. Players Bombus (pollinator) Bruchus (seed predator) Demographic costs of seeds and beetles

11. Field experiment Supplemental pollen increased seed set within the year BUT Next year’s flower production and growth reduced λ was negatively affected Ehrlen and Eriksson 1995, Ecology 69:652-656

12. End of story? NO! o Changing the demographic context can offset costs to λ o In variable environments o the currency for measuring the effects is λ s o frequency and sequence of high pollination years relative to other kinds of years determine outcome

13. Stages seeds seedlings small intermediate large vegetative large flowering dormant rhizome http://www.paghat.com/vetch.html Ehrlen and Eriksson 1995, Ecology 69:652-656

14. Open-pollinated

15. Ehrlen and Eriksson 1995, Ecology 69:652-656 Hand-pollinated

16. Costs to fates of large flowering plants and to λ Shrink Go Dormant Flower Less More seeds Data in Ehrlen and Eriksson 1995, Ecology 69:652-656

17. But 53% of seeds had been lost to beetles (both open and hand pollinated plants) Observed seeds = “Gross Seeds” - Beetles Beetles cost as much as seeds… Observed fates really for “Gross Seeds” Data in Ehrlen and Eriksson 1995, Ecology 69:652-656

18. Elimination of seed predators lessens negative effect on λ Data in Ehrlen and Eriksson 1995, Ecology 69:652-656

19. Demographic context: single constant environment (All simulations that follow use the predator-absent scenario)

20. Higher seed survival can compensate for cost

21. Higher germination can compensate for cost

22. Higher seedling survival can NOT compensate for cost

23. Demographic context: multiple environmental states (All simulations that follow use the predator-absent scenario)

24. 2-state model for variable environment Env at time t Env at time t+1 Probability rules that generate environmental sequences Columns sum to 1 Dot size indicates probability Color coded for environmental state to which the system transitions

25. 2-state IID models Increasing probability of going to a of going to a high pollination year high pollination year

26. Variable environments: Increasing frequency of high pollination year decreases fitness

27. Focus on world with 70% high, 30% low pollination What is the outcome of adding some high germination years among the low pollination years?

28. Now there are three environments Low pollination (as before) High pollination (as before) Low pollination accompanied by High (9x) germination λ = 1.063 λ = 1.055 λ = 1.157

29. 3-state IID models High germination any time

30. 3-state Markov models High germination only after high pollination

31. Variable environments: increasing frequency of high germination years increases fitness Sequence matters

32. Conclusions Changing the demographic context can offset costs to λ In variable environments the currency for measuring the effects is λ s frequency and sequence of high pollination years relative to other kinds of years determine outcome

33. Thanks o Rodolfo and John o 2006-08 NSF OPUS o Uppsala University o Stockholm University