The Effects of Geographic Origin on the Growth, Flowering Time and Fitness of an
Annual Legume Beyond its Native Range
Matt Cumming, Susana Wadygmar, and Arthur Weis
Department of Ecology and Evolutionary Biology, University of Toronto
Results – Differences in Flowering Time
Introduction
Species distributions that span large climatic gradients are often composed of populations that are adapted to
native environmental factors, such as the length of the local growing season. These adaptive traits frequently play
a key role in the success (or failure) of a particular population in a novel habitat. Previous studies have
demonstrated that the evolution of earlier flowering can enable a species to establish in territories north of their
current range boundaries, where growing seasons are shorter (Griffith and Watson 2006). If the timing of
flowering onset is critical to successful reproduction in areas where summers are shorter, then populations
previously adapted to environments with similar season lengths should perform better than those adapted to
longer summers when planted beyond their northern range edge. However, flowering too early often results in
less vegetative growth, which translates to less resource availability for seed production. Populations of
Chamaecrista fasciculata, a model legume, display local adaptation in traits such as flowering time along latitudinal
gradients (Etterson and Shaw 2001) making it an ideal candidate to examine how flowering time influences
population success beyond their current distributio,n and to determine if there is a trade off between the onset of
flowering and plant size.
Results – Vegetative Growth and
Reproductive Success
1)
All C. fasciculata populations were found to have unique flowering times
with populations from lower latitudes beginning to flower up to 50 days
later than those from the north (Fig 4.) Generally, the degree of
differences in flowering time between populations is correlated with the
magnitude of the geographic distance between them.
2)
The proportion of individuals that successfully reproduced is accurately
predicted by latitude (Fig 6.). A log linear regression comparing the
proportion of successfully reproducing individuals by population identified
northern populations(MN, PA, IL) as being far more likely to reproduce
when subjected to a shorter growing season than southern populations
(p< 0.001, Fig. 7). Furthermore, in comparing only northern populations,
our regression indicates that the population from furthest north (MN) will
have a higher proportion of individuals reach reproduction than the mid
latitude populations (p<0.05). The extent of reproductive success in a
population follows the same latitudinal cline as does the average onset of
flowering, indicating that flowering time may be a key trait involved in
northern range expansion.
Questions
1 - Do C. fasciculata populations from different latitudes of origin vary in flowering time?
Figure 4. Cumulative date of first flower for each population. All differences
in flowering time were found to be significant by means of Welch's ANOVA
(F(5,244)=220, p<0.0001).
2 - Is the probability of an individual successfully reproducing in a novel environment
predicted by its geographic origin?
3 - Is there a correlation between flowering time and vegetative growth, and how do they
interact to influence reproductive success?
Figure 8. Vegetative biomass and total seed mass are positively
correlated. North Carolina and Virginia are omitted due to negligible
seed mass
Methods
Chamaecrista fasciculata
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
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a frost intolerant prairie annual whose home range spans
from the northeastern United States to the midwest
indeterminate flowering
favours disturbed areas, open fields
Experimental Design
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
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Figure 5. 95% confidence intervals for the average mean difference in
first flower between pairs of populations(Games-Howell post hoc test). All
pairs have significantly different average dates of flowering onset.
Figure 1. Chamaecrista fasciculata in bloom
90 individuals from each of six population were planted in a common garden at the Koffler Science
Reserve at Jokers Hill (KSR) during the spring of 2010 in a 3m diameter hexagonal array with 20cm
spacing between individuals(Fig. 3)
Onset of flowering was recorded for all individuals and fruit were collected for a subset of each populations
Plants were harvested on day of first frost, and were dried and weighed.
Discussion
3)
Vegetative biomass and total seed mass positively covary in two out of the
four populations that successfully reproduced (Fig. 8). In these
populations, larger plants produce more seeds, and it seems logical that
plants that flowered later would be larger in size. However, when looking
at the correlation between flowering time and vegetative biomass, we see
that it is the earlier flowering plants that are the biggest (Fig. 9). We can
see from Fig. 10 that there is no clear interaction between flowering
phenology and plant growth on reproductive output in this species.
Future Directions
Planting density treatments (i.e. conspecific competition manipulation)
will be applied in a factorial design with artificial warming to examine
their interaction with growth, flowering time and fitness in the context of
global warming.
Results – Geographic Origin and
Reproductive Success
Figure 9. Vegetative biomass and the date of first flower are
negatively correlated.
Figure 6 - The proportion of
plants within a population that
successfully reproduced regressed
on the population's latitude of
origin (R2adj=0.91).
We will combine phenotypically distinct genetic backgrounds via
interpopulation crosses to produce a generation with broad continuous
distributions of our traits of interest. This will allow us to hone in on
optimal trait values while also breaking up any existing genetic
associations between traits that may hinder a population's ability to
respond to natural selection.
References and Acknowledgements
Etterson, J. and Shaw, R. (2001) Constraint to Adaptive Evolution in Response
to Global Warming. Science 294, 151-154.
Deviance Residuals
Min
IQ
Median
3Q
Max
-3.6235
-0.9989
-0.2386
1.3833
1.9676
Estimate
STD Err
Z value
Pr(>|z|)
(Intercept)
2.4852
0.0910
27.2990
<2e-16
N vs. S
0.5035
0.0901
6.6990
2.11e-11
NN vs. NS
0.1810
0.0725
2.497
0.0125
Coefficients:
Figure 2. Map of Western United States showing the native
range of C. fasciculata (Red line)and the locations of our six
sampled populations and the common garden site (KSR).
Figure 3. Hexagonal array containing 90
C. fasciculata individuals.
Deviances
Null Deviance:
95.010 on 11 degrees of freedom
Residual Deviance: 35.353 on 9 degrees of freedom
Figure 7. Log linear regression
confirms that there are differences
in reproductive success between
northern and southern populations
as well as between northern and
central populations.
Griffith and Watson (2006) Is Evolution Necessary for Range Expansion?
Manipulating Reproductive Timing of a Weedy Annual Transplanted beyond Its
Range. The American Naturalist 167 2: 153 - 164.
Special Thanks to:
Figure 10. The combined interaction of vegetative growth and
flowering time on seed production. Size of bubble denotes the
magnitude of seed mass produced with respect to the individuals
flowering time and vegetative biomass
Bruce Hall, and Andrew Petrie
All the Undergraduate volunteers
Emily Austen
Dr. Jennifer Ison