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UBC BLISS talk 2016
- 1. Cascading effects of spatial structure across trophic levels Rachel M. Germain Killam/Biodiversity Postdoctoral Fellow Main collaborators: Natalie Jones, Tess Grainger, Ben Gilbert, Andrew MacDougall
- 2. Community ecologist: species coexistence and metacommunities Schematic modified from Velland 2016 Botany seminar Oct. 11th @12:30pm env gradient
- 3. Collaborators Tess Grainger Natalie Jones Ben Gilbert
- 4. Biological communities rarely exist in isolation ‘metacommunity’ biotic/abiotic environment
- 5. Predictions of island biogeography/metapopulation theories species richness/ site occupancy larger, less isolated patches species richness/ site occupancy smaller, more isolated patches MacArthur & Wilson 1967; Hanski 1994
- 6. Predictions of island biogeography/metapopulation theories species richness/ site occupancy larger, less isolated patches species richness/ site occupancy smaller, more isolated patches MacArthur & Wilson 1967; Hanski 1994
- 7. Spatial constraints likely vary among species sessile vs. motile, dispersal ability, cognitive function → behavior (habitat selection, territory, predator avoidance), body size, matrix sensitivity, etc.
- 8. P C2 C1 C3 Cascading spatial dynamics among trophic levels patch isolation patch size spatial patterns spatial patterns
- 9. Multi-trophic extensions of island biogeography and metacommunity theories Trophic dependency: predators can only establish in patches that already contain their prey • prey must outpace their predators • predator distributions should be a subset of prey distributions • IBT patterns should be stronger at higher trophic levels Holt 2002 EcoRes; Leibold et al. 2004 EcoLett; Harvey & MacDougall 2014 Ecology Assumes that predators: are specialists, are bound to same habitat patches as their prey, and experience the world at the same spatial scales as their prey
- 10. What are the consequences for diversity in systems where spatial constraints differ within and among trophic levels? aspen-understory plants Jones, Germain, et al. 2015 JEcology tall-grass prairie plants Germain et al. 2013 AmNat milkweed insect specialists Grainger, Germain, et al. in review Ecology
- 11. What are the consequences for diversity in systems where spatial constraints differ within and among trophic levels? aspen-understory plants Jones, Germain, et al. 2015 JEcology tall-grass prairie plants Germain et al. 2013 AmNat milkweed insect specialists Grainger, Germain, et al. in review Ecology
- 12. Tall-grass prairie restoration efforts in SW Ontario
- 13. System: tall-grass prairie plant communities
- 14. System: tall-grass prairie plant communities How does risk avoidance behavior by small mammals affect spatial patterns in plant communities? predation risk cognition yes yes no range size
- 15. Predation risk increases with distance from old-field edge pre- prairie more removal less removal old- field Prediction:
- 16. Closed old-field Pre-prairie -30 -10 10 30 50 70 90+ Distance from edge (m) Prop.seedsremoved F1,84 = 150.9, P < 0.0001* Seed removal was strongest in the old-field, and decreased with distance from the edge
- 17. Consequences of small mammals for plant diversity depends on foraging selectivity Cafeteria trial w/ 8 plant species from 3 functional groups B. kalmii H. divaricatus R. blanda
- 18. 0 2 4 6 8 10Seedsremaining Seed species Forb seeds were consumed significantly more than shrub and grass seeds Functional group: F2,23 = 29.97, P < 0.001* Species: F5,23 = 0.35, P = 0.876 Forbs Shrubs Grasses
- 19. P = 0.012*F1,48 = 12.82, P <0.001* β-diversity(Jaccard’sdissimilarity) α-diversity(speciesperplot) α β Distance from edge (m) Distance from edge (m) What does this all mean for plant community distributions?
- 20. What does this all mean for plant community distributions? P = 0.012*F1,48 = 12.82, P <0.001* β-diversity(Jaccard’sdissimilarity) α-diversity(speciesperplot) α β Distance from edge (m) Distance from edge (m)
- 21. oldfield increasing β-diversity decreasing seed predation prairie interior Net effect: emergent patterns in plant diversity that reflect risk environment
- 22. What are the consequences for diversity in systems where spatial constraints differ within and among trophic levels? aspen-understory plants Jones, Germain, et al. 2015 JEcology tall-grass prairie plants Germain et al. 2013 AmNat milkweed insect specialists Grainger, Germain, et al. in review Ecology
- 24. System: milkweed insect specialists habitat use generalist milkweed specialist
- 25. Milkweed specialists differ in susceptibility to predators and dispersal ability Constrained by predation1: yes 1Duffey & Scutter 1972, Zalucki & Kitching 1982, Smith et al. 2008 2Jones & Parella 1986, St Pierre & Hendrix 2003, McCauley et al. 1981 no yes no Constrained by size/isolation2: <100 m >1000 m
- 26. Predictive framework for island biogeography informed by natural history P, S, I S, Inone P Patchoccupancy Patch size/isolation P = predator, S = size, I = isolation Do constraints of patch size/isolation vary among species, and are they altered by predation?
- 27. Field surveys of milkweed patches Patch isolation Patch size (m2) 𝐼𝑖 = 1 − 𝑗≠𝑖 𝑛 𝐴𝑗 𝑒 −𝑑 𝑖𝑗 𝛼 Hanski 1994 TREE Presence/absence data Predator abundances occupancy ~ patch size x patch isolation x predator abundances
- 28. Predictive framework for island biogeography informed by natural history none P N.S. Patch isolation Occupancy P, S, I S, I P = predator, S = size, I = isolation
- 29. Predictive framework for island biogeography informed by natural history none P P = predator, S = size, I = isolation P, S, I S, I
- 30. Predictive framework for island biogeography informed by natural history none P P = predator, S = size, I = isolation P, S, I S, I Zalucki & Kitching 1982a JZoology, Zalucki & Kitching 1982b Oecologia “More eggs were laid per plant on single isolated plants than on plants within a patch” “The trend was for increasing [mortality] with increasing patch size” → predation
- 31. Predictive framework for island biogeography informed by natural history none P P = predator, S = size, I = isolation P, S, I S, I
- 32. Tying it all together… Dispersal-limited species were directly affected by spatial constraints Predation affected palatable species indirectly through interactions with spatial drivers Incorporating predator-avoidance tactics (refuge seeking and crypsis) can help refine predictions
- 33. Biogeographic constraints highly variable among species in this community – but fairly predictable Matrix-dwelling predators can weaken or modify the effects of spatial drivers
- 34. What are the consequences for diversity in systems where spatial constraints differ within and among trophic levels? aspen-understory plants Jones, Germain, et al. 2015 JEcology tall-grass prairie plants Germain et al. 2013 AmNat milkweed insect specialists Grainger, Germain, et al. in review Ecology
- 36. System: Aspen understory plant communities Do effects of stand size and isolation on species distributions vary with dispersal mode? cognition yes no range size
- 37. Field surveys of aspen stands 𝐼𝑖 = 1 − 𝑗≠𝑖 𝑛 𝐴𝑗 𝑒 −𝑑 𝑖𝑗 𝛼 Hanski 1994 TREE Stand characteristics size (m2) isolation stand age Presence/absence data Dispersal mode No aid Wind Animal Aspen stand Adjacent grassland
- 38. Predicted effects of stand size and isolation for different dispersal modes No aid Wind-dispersed Animal-dispersed
- 39. Observed effects of stand size and isolation for different dispersal modes No aid Wind-dispersed Animal-dispersed competition among dispersal modes? ruderal species and disturbance?
- 40. Paired plot design to identify aspen specialists vs. generalists or grassland specialists Quantifying species affinity for aspen stands all species included occurs in aspen stands ≥50% of the time occurs in aspen stands ≥ 66% of the time occurs in aspen stands ≥75% of the time cut-off is not always clear in “diffuse” metacommunities Cook et al. 2002 EcoLett; Leibold et al. 2004 EcoLett metacommunity = species that occur in favourable habitat patches imbedded in a matrix of unfavourable habitat
- 41. The results are insensitive to cut-off, except when all species are included SR ~ stand size Matrix-associated species can obscure metacommunity processes – paired plot design is one day to discount their effects
- 42. IBT patterns are somewhat consistent with our initial predictions, but … There are three complicating factors: • dispersal mode • unexplained inconsistencies • grassland specialists + generalists
- 43. …and so, to summarize… ability to persist in matrix habitat = modifications to biogeographic constraints in insect species that are sensitive to predators greater habitat use by granivores in low risk areas = gradients in ecological filters that dictate plant species distributions habitat selection by animals = non-IBT patterns for animal-dispersed plant species
- 44. “patch area and isolation are surprisingly poor predictors of occupancy for most species” data from 1,015 bird, mammal, reptile, amphibian, and invertebrate population networks metapopulation metacommunity∑ =
- 45. Island biogeography in non-island systems suitable habitat unsuitable habitat
- 46. Island biogeography in non-island systems suitable habitat unsuitable habitat Are patch size and isolation unimportant compared to/in combination with local factors? How do spatial dynamics cascade across trophic levels? How do spatial dynamics change with species additions or losses at different trophic levels? Should conservationists only be focusing on patch size/isolation?
- 47. Acknowledgements Co-authors Natalie Jones Tess Grainger Ben Gilbert Aaron Hall Lynn Baldwin Andrew MacDougall Karl Cottenie Laura Johnson Elizabeth Gillis Webpage: rgermain.wordpress.com Email: rgermain@zoology.ubc.ca Office: BIODIV245
- 48. Monarch caterpillar mortality as a function of stand size
- 49. PCoA testing turnover in proportion of species belong to each dispersal modes