examining coexistence between splachnaceae mosses with individual-based modelling

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

cfhammill@gmail.com

Paul Marino

pmarino@mun.ca

Slides: datamancy.blogspot.ca

Contact

Chris Hammill

cfhammill@gmail.com

Paul Marino

pmarino@mun.ca

Slides: datamancy.blogspot.ca

Any Questions?