Internal Seminar: Juanita Choo (Science and Technology Group)

Internal Seminar: Juanita Choo (Science and Technology Group). Language: English, no interpretation.

Title:  Life history traits influence the strength of distance- and density-dependence at different life stages of two Amazonian palms

Abstract: 

Natural enemies are known to be important in regulating plant populations and contributing to species coexistence (Janzen–Connell effects). The strength of Janzen–Connell effects (both distance- and density-effects) varies across species, but the life history traits that may mediate such a variation are not well understood. This study examined Janzen–Connell effects across the life stages (seed through adult stages) of two sympatric palm species with distinct phenologies and shade tolerances, two traits that may mediate the strength and timing of Janzen–Connell effects.  

Methods: Populations of two common palm species, Attalea phalerata and Astrocaryum murumuru, were studied in Manu National Park, Peru. Seed predation experiments were conducted to assess Janzen-Connell effects at the seed stage. In the post-seed stages, spatial point pattern analyses of the distributions of individuals and biomass were used to infer the strength of distance- and density-effects.

Results: Seed predation was both negative distance- and density-dependent consistent with the Janzen–Connell effects. However, only seedling recruitment for asynchronously fruiting Attalea phalerata was depressednear adults while recruitment remained high for synchronously fruiting Astrocaryum murumuru, consistent with weak distance-effects. Negative density-effects were strong in the early stages for shade-intolerant Attalea phalerata but weak or absent in shade-tolerant Astrocaryum murumuru. 

Conclusion: Distance- and density-effects varied among the life stages of the two palm species in a manner that corresponded to their contrasting phenology and shade tolerance. Generalizing such connections across many species would provide a route to understanding how trait-mediated Janzen–Connell effects scale up to whole communities of species.

Free pizza and soft drinks will be served following the Internal Seminar: please bring a mug! We hope to see you there!

Sincerely,

Internal Seminar Organizing Committee:

Marylka Yoe Uusisaari

Yasha Neiman

Rob Campbell

Margaret Mars Brisbin

Maéva Techer

Jigyasa Arora

Yuka Suzuki

Andreas Thomasen

Kun-Lung Li