examining coexistence between splachnaceae mosses with individual-based modelling
DESCRIPTION
99th ESA annual meeting talk about my masters work with Splachnaceae mosses coexisting in peatlands in Newfoundland, Canada. Individual-based modelling was used to look at key factors influencing coexistenceTRANSCRIPT
Studying Coexistence Between MossesWith Individual Based Modelling
Presented by Chris HammillFor The ESA Annual Meeting 2014
Road Map
● Where I Work● My Study Organisms● About the Model
- Space- Agents- Interactions
● Analysis● Results● Take Home Messages
Splachnaceae
➢ Globally Distributed
➢ 50% are Coproentomophilous
➢ Coprophily:
Habitat specialists for dung or carrion
➢ Entomophily (Myophily):
A specialized dispersal strategy using flies as spore
dispersal vectors
Meet the Mosses
Splachnum pensylvanicumSplachnum ampullaceum
Splachnum MossesIn Newfoundland Peatlands
➢ Two Species:Splachnum ampullaceum and S. pensylvanicum
➢ Found on moose dung
➢ Grow in pure and mixed populations
➢ Share many fly vectors
➢ Differ in attraction cues
➢ Seem to inhabit the same niche
➢ Two Species:Splachnum ampullaceum and S. pensylvanicum
➢ Found on moose dung
➢ Grow in pure and mixed populations
➢ Share many fly vectors
➢ Differ in attraction cues
➢ Seem to inhabit the same niche
Splachnum MossesIn Newfoundland Peatlands
So: How do they coexist?
The Model
● Spatial Considerations
● Individuals
● Interactions
Space and Substrate
● Circular Peatland
● New substrate deposited on random days
● New substrate deposited at random locations
Arena
The Model
● Spatial Considerations
● Individuals
● Interactions
My Model
My ModelMature Moss
My ModelMature Moss
Fresh Dung
My ModelMature Moss
Fresh Dung
Immature Moss
My Model
My Model
My Model
My Model
My Model
My Model
The Model
● Spatial Considerations
● Individuals
● Interactions
Competition
Competition
➢ Each new year, former dung piles become immature moss
populations
➢ Starting conditions for competition are determined by spore
allotment from dispersal
➢ Moss protonemata compete for space according to
Discrete Lotka-Volterra dynamics
Dispersal
Spore Transfer
Governing Factors
Distance Yield and composition of mature moss Attractiveness of the dung Phenology
(1)
(2)
D
∑D
• Transfer is proportional to moss attractiveness
• Transfer only effective when dung is more attractive than moss
• Transfer is proportional to the attractiveness difference between moss and dung
Influence of Attractiveness
Model Phenologies
Uniform and harmonic functions used to describe percent areal coverage producing sporophyes
Model Construction
● Model Written in Java
● Simulations run for 1000 year
● Year end peatland snap-shots
● 3 – 30 Mb per simulation
● Post processing and summarization done in R
Big Question
Which parameters are most important in permitting coexistence?
Varied Parameters
● Dung deposition rate (Substrate; 10x)
● Geometric growth rate (Competition; 10x)
● Attractiveness (Magnitude Dispersal; 10x)
● Phenology (Timing Dispersal; 5x)
5000 Total Combinations
Analysis
● Ran simulations at predetermined parameter combinations
● Summarized each simulation● Determined the average ratio of
The two species● Create a Random Forest of Regression Trees.● Examine Variable Importance Measures
Random Forest Results
Parameter Importance
Phenology 0.1626
Growth Rate 0.0927
Dung Deposition 0.0818
Attractiveness 0.0737
*R2 = .947
Question Two
What Role Does Dispersal Play in Coexistence?
Question Two
What Role Does Dispersal Play in Coexistence?
● What Role Does Attraction Play● What Role Does Phenology Play
Influence of AttractivenessTim
e C
oexist e
d (y
ears)
Influence of AttractivenessTim
e C
oexist e
d (y
ears)
Influence of AttractivenessContinued
Time C
oexist e
d (y
ears)
Influence of Phenology
Two competitors with identical phenology
Time C
oexist e
d (y
ears)
Influence of Phenology Continued
Two competitors with opposite phenologies
Time C
oexist e
d (y
ears)
Take Home Messages
● Staggered phenologies are sufficient to offset huge competitive differences
● Achieving near optimal attractiveness is important for reducing odds of extinction
Acknowledgements
Drs. Paul Marino, Suzanne Dufour, Amy Hurford, Shawn Leroux, Lourdes Pena-Castillo, and Tom Chapman
Andrew Chaulk, Greg Dickson, Jenna Paul, Olga Trela
And ESA for giving me this opportunity to share my work
Contact
Chris Hammill
Paul Marino
Slides: datamancy.blogspot.ca
Any Questions?