The influence of physiological traits on climatic niche
occupancy and competitive ability in the polyploid plant,
Chamerion angustifolium (Onagraceae)
Ken A. Thompson, Brian C. Husband, Hafiz Maherali
University of Guelph, Department of Integrative Biology
Guelph, ON. N1G 2W1
Photo: Brian Husband
What is polyploidy?
• Whole genome multiplication
• Instantaneous “speciation”
• Associated with angiosperm diversification (Albert et al.
2013. Science 6165)
2x
4x
stemcellthailand.org
Amborella trichopoda (wikipedia.org)
Polyploidy Influences Plant Function
• Often increased cell size in polyploids
• Cell size influences organ size
– Influences physiology
2x
4x
2x
stemcellthailand.org
4x
Photo: Brian Husband
Polyploidy and Distribution
• How do physiological differences between
cytotypes influence their geographic distributions?
2x
4x
Photo: Brian Husband
1. Do physiological traits influence the climatic
niche of diploid and polyploid cytotypes?
2. Do physiological traits influence the
competitive abilities of diploid and polyploid
cytotypes?
Study System: Fireweed
• Chamerion angustifolium (Onagraceae)
• Diploid (2n = 2x = 36) and tetraploid (2n = 4x = 72) cytotypes
• Cytotypes occupy largely distinct geographic ranges
Photo: Brian Husband
Cytotype Physiology in Fireweed
• Tetraploids tolerate drought better than diploids, but are more
vulnerable to freezing damage (Maherali et al. 2009. New Phytol. 184)
4x
Cytotype Physiology in Fireweed
• Tetraploids tolerate drought better than diploids, but are more
vulnerable to freezing damage (Maherali et al. 2009. New Phytol. 184)
• Caused by differences in xylem conduit diameter
2x
4x
1. Do physiological traits influence the climatic
niche of diploid and polyploid cytotypes?
2. Do physiological traits influence the
competitive abilities of diploid and polyploid
cytotypes?
• Tetraploid C. angustifolium tolerate drought
– Tetraploid niche will be drier than the diploid niche
• Diploid C. angustifolium resist freezing
– Diploid niche will be colder than tetraploid niche
Characterizing the Climatic Niche
• Extracted climate data with GIS
– 134 C. angustifolium populations
– Pure Diploid, Mixed-Ploidy, Pure Tetraploid
• Univariate climate variable comparisons
Total
Season
Season
Growing
TotalGrowing
Water
DefificDeficit
( mm )(mm)
Moisture
Soil
Tetraploids occupy driest habitats
100
0
-100
-200
-300
A
AB
B
ANOVA F = 5.732
p < 0.01
Mean Minimum Growing
Season Temperature ( °C )
Diploids occupy coldest habitats
8
6
4
2
0
-2
A
A
B
ANOVA F = 31.33
p < 0.001
Physiological traits correlated with
climatic niche
Do physiological traits influence the climatic niche
of diploid and polyploid cytotypes?
• Physiological traits
generate accurate
predictions of cytotype
niches in C. angustifolium
• Biotic interactions also
limit fundamental niche
1. Do physiological traits influence the climatic
niche of diploid and polyploid cytotypes?
2. Do physiological traits influence the
competitive abilities of diploid and
polyploid cytotypes?
• Tetraploids can tolerate drought
– Tetraploids will be better competitors than
diploids in dry soils
Experimental Design
• 864 plants in 180 pots
• 15 competition treatments at 7 densities
Applying Irrigation Treatments
Aboveground Dry Biomass (g)
• Two irrigation treatments
• Well watered and drought treatments independently
controlled
*p < 0.01 ANOVA
*
*
Diploid
Tetraploid
Analysis of Competition Experiment
• Reciprocal-yield model
– Multiple linear regression
1
W𝑑
= b𝑑0 + 𝑏𝑑 N𝑑 + 𝑏𝑡 N𝑡 + N𝑑 N𝑡 + 𝜌𝑖
Intracytotypic
competition competition
Intercytotypic
Reciprocal biomass of an
individual diploid plant
Diploid density
Tetraploid density
Analysis of Competition Experiment
• Reciprocal-yield model
– Multiple linear regression
1
W𝑑
= b𝑑0 + 𝒃𝒅 N𝑑 + 𝒃𝒕 N𝑡 + N𝑑 N𝑡 + 𝜌𝑖
– Test for difference between 𝒃𝒅 and 𝒃𝒕
RECIPROCAL
BIOMASS (g)
RECIPROCAL
BIOMASS (g)
DENSITY OF
DIPLOIDS
DENSITY OF
TETRAPLOIDS
DENSITY OF
DIPLOIDS
DENSITY OF
TETRAPLOIDS
Equal Competitive Abilities
Different Competitive Abilities
𝑏𝑑 = 𝑏𝑡
𝑏𝑑 ≠ 𝑏𝑡
Equal Competitive Abilities in WellWatered Treatment Pots
DIPLOID
RESPONSE
TETRAPLOID
RESPONSE
𝑏𝑑 = 𝑏𝑡
𝑏𝑑 = 𝑏𝑡
Equal Competitive Abilities in Drought
Treatment Pots
DIPLOID
RESPONSE
TETRAPLOID
RESPONSE
𝑏𝑑 = 𝑏𝑡
𝑏𝑑 = 𝑏𝑡
Cytotypes are equally competitive
Do physiological traits influence the competitive
abilities of diploid and polyploid cytotypes?
• No difference in
competitive ability
between cytotypes in
either watering
treatment
• Drought tolerance does
not increase tetraploid
competitive ability
• Physiological traits can be used to predict the
climatic niches of C. angustifolium cytotypes
• Competition for water probably not restricting
cytotype distribution
– Drought could influence earlier life stages
– Competition and temperature?
Thank You!
• Acknowledgements
– Paul Kron—Flow Cytometry
– Mike Mucci—Irrigation System
– NSERC Discovery, Canada Foundation for Innovation, Canada Research
Chair Program grants to BCH and HM
Super Secret Extra Slides
http://clipartist.info/clipart/halloween/plain_ghost-1979px.png
Ploidy Screening
• Used flow cytometry to screen over 300 fruits
Number of Nuclei
– Compare sample DNA content to a known standard
Tomato
(DNA
Standard)
Diploid
(2x)
Tetraploid
(4x)
Fluorescence Area
Principal Components Analysis
• Supports unique climatic niche hypothesis
Principal Component 2
3
MIN TEMP
MEAN TEMP
MAX TEMP
MEAN PREC
MEAN PET
2
1
0
-1
Pure Diploid
Mixed-Ploidy
Pure Tetraploid
-2
-3
-4
-3
-2
-1
0
1
2
Principal Component 1
3
4
Niche Modelling
• Models produce predictions that are similar to the
estimated geographic distributions
Diploid
Niche Modelling
• Models produce predictions that are similar to the
estimated geographic distributions
Tetraploid