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An examination of the spatial dimensions of pollination facilitation in an arid ecosystem

Proposed thesis project and introduction to major mechanisms of pollination facilitation.

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An examination of the spatial dimensions of pollination facilitation in an arid ecosystem

  1. 1. An examination of the spatial dimensions of pollination facilitation in an arid ecosystem. Jenna Braun Thesis Proposal – 1st Committee Meeting November 16 2016
  2. 2. Positive Interactions
  3. 3. Pollination Facilitation
  4. 4. Mechanisms  Increased size of co-flowering display  Increased diversity of floral display  Pollinator support: Sequential Mutualism/Community Stability  Magnet species
  5. 5. Magnet Hypothesis  Presence of a more attractive species increases pollination of a less attractive species or to a mixed assembly of species  Predicts that the effect is greater than only increasing floral abundance
  6. 6. Shrubs and cacti as magnets
  7. 7. Scale Grain – size of the sampling unit. Can be pixel, focal plant, plot, patch. Extent – total area over which sampling occurs. Data vs. model Do individual interactions matter at larger scales? What is the effect of a magnet species on its neighbours? Neighborhood? Patch? Landscape?
  8. 8. Landscape Neighborhood Plot Plant
  9. 9. A systematic review contrasting pollinator facilitation in desert shrubs and cacti.  Determine support for current hypotheses and identify any research gaps.  Is current literature is reporting scale in a meaningful, replicable way? CH1
  10. 10. Hypothesis: Pollinator facilitation neglects scale but the spatial component of plant-pollinator interactions is an important research gap. CH1
  11. 11. Figure 1: PRISMA diagram (Moher et al, 2009) of workflow for pollination facilitation systematic review. Papers obtained through database searching (Web of Science), Keywords: Pollinat* facilitat* shrub Pollinat* facilitat* cact* Pollinat* competit* shrub Pollinat* competit* cact* (n = 169) ScreeningIncludedEligibilityIdentification Papers obtained from other sources, such as book chapter bibliographies Records after duplicates removed (n = 169) Records screened by abstract (n = ) Records excluded for: Relevance Review, opinion or idea paper Full-text articles assessed for eligibility (n = ) Full-text articles excluded: Not testing facilitation or competition (n = ) Not testing interspecific interactions (n = ) Focal species wind-pollinatedInclude in synthesis (n = ) Extract data: Location Ecosystem Experiment type:(manipulative, mensurative) Hypothesis tested Relative/Absolute Scale Number of scales Scale dependence CH1
  12. 12. A spatially explicit survey of pollination facilitation between Mojave Desert perennials and annuals.  Does the strength of pollination facilitation vary with guild (annual/perennial)?  How does shrub and cacti density and spatial distribution interact to influence pollinator behavior? Kelso DunesUC, Riverside CH2
  13. 13.  All shrubs and cacti will be georeferenced using high- resolution GPS, tagged and identified to species.  Determine a natural replacement series of shrub:cacti CH2
  14. 14. Phenology  Floral surveys every 8 -10 daysFloralAbundance Time Shrubs Annuals Cacti CH2
  15. 15. Seed Collection: Shrubs: 3 * 10cm diameter circle - mean Cacti: 3 per cacti – Will need to weigh Annuals: 3 seed heads * 3 species per paired microsite: Microsite species should match understory CH2
  16. 16. Pollen  As visitation by shared pollinators increases, heterospecific pollen transfer may also increase  A “cost” of pollinator sharing  Can create a pollen transfer network  Hub donors with positive effects on receivers – magnets CH2
  17. 17. Predictions: Cacti will be non-randomly distributed around shrubs Association of shrubs with cacti will be species-specific Hypothesis: Shrubs facilitate cacti through stress-amelioration CH2
  18. 18.  Annuals growing under shrubs or cacti will have greater seed set and pollen deposition than annuals growing in paired open site Hypothesis: Shrubs facilitate cacti and annual plant reproduction by attracting shared pollinators. CH2 Seedset,pollendeposition Open Understory
  19. 19. Hypothesis: Pollination facilitation shows scale-dependence because pollinators make different foraging decisions at different scales Prediction:  Seed set and pollen transfer to understory and open annuals will decrease with increasing distance from cacti or shrubs. CH2
  20. 20. Prediction:  At small scales higher floral densities will lead to increased pollinator visits, pollen deposition and seed set but at larger scales the interaction will change to neutral or negative CH2 Distance
  21. 21. A contrast of local and regional density effects on pollinator facilitation. • How does the density and distribution of shrub-annual complexes (magnets) affect visitation to low and high densities of annuals? CH3
  22. 22. Low High Low High Annual Density Shrub Density 4 replicates (1.5 hours) * 4 treatments * 8 days CH3
  23. 23. PollinatorVisitationRate Low LowHigh High Annual Density Low Shrub Density High Shrub Density CH3