3. Leaf diversity
• Leaves are the
organs primarily
responsible for
photosynthesis
• Evolutionary
patterns of leaf
variation are not
well understood
(Jones et al. 2008)
Leaf variation in Pelargonium. Image from Nicotra et al. 2011
3
4. Introduction to Ficus
• Ficus is a large pan-tropical genus with >800
species
• Lot of variation in life history patterns and
ecology, with an equally complex evolutionary
history (Harrison 2005)
• Leaves within the genus exhibit tremendous
diversity
4
5. Hemiepiphytic Ficus
• Many Ficus species have a “hemi-epiphytic” life
style
• Epiphytic stage
associated with
water stress
(Holbrook & Putz
1996, Hao et al.
2010)
Epiphytic and Terrestrial F. concinna, from Hao G.Y., et al. 2010
5
7. Leaf size variation
• Large leaves require more “structure” to hold up
against gravity (Niklas 1999)
– Structure might come in many ways (Westbrook et al.,
2012)
• For large leaves to evolve, ancestors needed to
have leaves with greater structure
7
8. Hypotheses
• HI: Hemiepiphytic figs have evolved to deal
with water stressed environments
– Prediction: Hemiepiphytic figs have smaller leaves
with lower specific leaf area (SLA), even when
grown in common gardens with terrestrial figs
• HII: Large leaves are harder to hold up than
small leaves; thus they need to be tougher
– Prediction: Leaf size ~ Leaf lamina toughness
– Prediction: Leaf size and leaf toughness show
patterns of correlated evolution
8
10. Methods
• Sampling intensity:
– 2 trees/species; 3 leaves/tree
• Leaf traits measurements according to
published protocols (Perez-Harguindeguy et al. 2013)
– Leaf Area, Toughness, and SLA
• Life history data (i.e. epiphytic/terrestrial)
collected from the Flora of China (eFloras 2008)
10
11. F hispida
F fistulosa
F semicordata
●
F sur
F beipeiensis
F auriculata
F oligodon
Phylogenetic
Methods
• Used a published Ficus
phylogeny (Cruaud et al.
●
F racemosa
F tikoua
F villosa
F sarmentosa
F deltoidea
F stenophylla
F ischnopoda
F hirta
F ruficaulis
F tinctoria
F subulata
F cyrtophylla
F henryi
●
2012)
• Thirty species shared
between XTBG Ficus
collection and the
phylogeny
●
●
F concinna
F cyathistipula
●
●
F virens
F religiosa
●
●
●
●
F stricta
●
F maclellandii
F benjamina
●
●
●
F altissima
F annulata
F glaberrima
●
●
●
11
12. Data Analysis
• Testing prediction 1
– T-Tests to compare leaf area and SLA of HE/Ter
• Testing prediction 2
– Test for relationship between Leaf Area and
Toughness
• Testing prediction 3
– Ancestral Trait Reconstruction and Phylogenetically
Independent Contrasts (PICs) of Area and Toughness
in R package phytools (Felsenstein 1985; Revell 2012)
12
13. Results
F hispida
F fistulosa
F semicordata
F sur
F beipeiensis
F auriculata
F oligodon
F racemosa
F tikoua
F villosa
F sarmentosa
F deltoidea
F stenophylla
F ischnopoda
F hirta
F ruficaulis
F tinctoria
F subulata
F cyrtophylla
F henryi
F virens
F religiosa
F concinna
F cyathistipula
F stricta
F maclellandii
F benjamina
F altissima
F annulata
F glaberrima
SLA
Area Toughness
13
14. Results
• Prediction 1 (Hemiepiphytes ~ smaller leaves with low SLA)
Log Area of HE and Terrestrial Ficus species
SLA of HE and epiphytic and terrestrial Ficus specie
SLA variation between Terrestrial Ficus species
250
p=0.40
200
150
SLA
5
100
4
3
Area
log logArea
6
p=0.90
Epi
Ter
Epi
Ter
14
15. Results, cont.
• Prediction 2 (Leaf area ~ Leaf toughness)
Log Area vs. Toughness
5
4
3
log Area (cm^2)
6
p=0.91
200
400
600
800
1000
1200
1400
Toughness (N/m^2)
15
17. Reconstruction of Toughness
Reconstruction of log Area
F hispida
F hispida
F hispida
F hispida
F fistulosa
F fistulosa
F fistulosa
F fistulosa
F semicordata
F semicordata
F semicordata
F semicordata
F sur
F sur
F sur
F sur
F beipeiensis
F beipeiensis
F beipeiensis
F beipeiensis
F auriculata
F auriculata
F auriculata
F auriculata
F oligodon
F oligodon
F oligodon
F oligodon
F racemosa
F racemosa
F racemosa
F racemosa
F tikoua
F tikoua
F tikoua
F tikoua
F villosa
F villosa
F villosa
F villosa
F sarmentosa
F sarmentosa
F sarmentosa
F sarmentosa
F deltoidea
F deltoidea
F deltoidea
F deltoidea
F stenophylla
F stenophylla
F stenophylla
F stenophylla
F ischnopoda
F ischnopoda
F ischnopoda
F ischnopoda
F hirta
F hirta
F hirta
F hirta
F ruficaulis
F ruficaulis
F ruficaulis
F ruficaulis
F tinctoria
F tinctoria
F tinctoria
F tinctoria
F subulata
F subulata
F subulata
F subulata
F cyrtophylla
F cyrtophylla
F cyrtophylla
F cyrtophylla
F henryi
F henryi
F henryi
F henryi
F virens
F virens
F virens
F virens
F religiosa
F religiosa
F religiosa
F religiosa
F concinna
F concinna
F concinna
F concinna
F cyathistipula
F cyathistipula
F cyathistipula
F cyathistipula
F stricta
F stricta
F stricta
F stricta
F maclellandii
F maclellandii
F maclellandii
F maclellandii
F benjamina
F benjamina
F benjamina
F benjamina
F altissima
F altissima
F altissima
F altissima
F annulata
F annulata
F annulata
F annulata
F glaberrima
F glaberrima
F glaberrima
F glaberrima
3.05
trait value
6.787
6.787
2
20 cm3.05trait value 800 cm2
length=0.023
length=0.023
239.572
1374.305
239.572 200 grams trait value 1500
trait value
1374.305
length=0.023
length=0.023
grams
17
18. Results, cont.
• Prediction 3
PICs of Log Area vs. PICs of Toughness
1
0
-1
-2
PICs of log area
2
p = 0.34
p=0.36
-500
0
500
PICs of toughness
1000
18
19. Discussion
• Prediction 1 (Hemiepiphytic figs ~ low leaf area and SLA)
– Not supported
– Environmental factors drive reported leaf variation
(e.g. Holbrook & Putz 1996)
– Hemiepiphytes may have evolved other mechanisms
to deal with water stress
19
20. Discussion
• Prediction 2 (Leaf area ~ lamina toughness)
– Not supported
– Veins and petioles may be sufficient to support large
leaves.
• Prediction 3 (Leaf area ~ lamina toughness across phylogeny)
– Not supported
– Evolution of leaf size and toughness not correlated
across the phylogeny
20
21. Discussion: Limitations
• Sampling intensity may not have accounted for
intraspecific variation in leaf traits
• Unbalanced data set to test Hypothesis I
• Ficus phylogeny is still being developed (e.g. Yao
et al. 2013), and our methods are sensitive to the
phylogeny used
21
22. Future Directions
• The evolutionary history of leaves is not well
understood
• Ficus is an ideal group to study this diversity
– Morphological, distributional, and life history
variation
• Studies based on leaf
morphology, structure, venation, and
architecture (Nicotra et al., 2011)
• Characterize leaf transcriptomes
– Determine molecular basis for variation
22
23. Acknowledgements
• AFEC Instructors and Organizers
– Liu Jing-Xin, Drs. Richard Corlett, Alice Hughes, Kyle
Tomlinson, Uromi Goodale, Eben Goodale, Ferry Slik
– Other XTBG research groups, especially the
Evolutionary Ecology, Plant Ecophysiology, and PlantAnimal Interaction groups, and Pan Bo for helping
with Ficus identification
• XTBG Ficus collection management staff
• Numerous tutorials/guides to comparative
phylogenetics in R
23
24. References
•
•
•
•
•
•
•
•
•
•
•
Cruaud, A., et al. 2012. An extreme case of plant-insect codiversification: figs and figpollinating wasps. Systematic Botany 61(6), 1029-1047
Felsenstein K. 1985. Phylogenetics and the comparative method. American Naturalist
125, 1-15..
Hao, G-Y., et al. 2010. Differentiation in leaf water flux and drought tolerance traits in
hemiepiphytic and non-hemiepiphytic Ficus tree species. Functional Ecology 24(4), 731740
Harrison, R.D. 2005. Figs and the diversity of tropical rainforests. BioScience
55(12), 1053-1064.
Holbrook, N.M., and Putz, F.E. 1996. From epiphyte to tree: differences in leaf structure
and leaf water relations associated with the transition in growth form in eight species of
hemiepiphytes. Plant, Cell and Environment 19, 631-642.
Jones, C.S., et al. 2008. Leaf shape evolution in the South African genus Pelargonium
L’He’R. (Geraniaceae). Evolution 63-2, 479-497
Niklas, K.J. A mechanical perspective on foliage leaf form and function. New Phytologist
143, 19-31.
Nicotra, A.B., et al. The evolution and functional significance of leaf shape in the
Angiosperms. Functional Plant Biology 38, 535-552
Revell, L.J. phytools: an R package for phylogenetic comparative biology (and other
things). Methods in Ecology and Evolution 3(2), 217-223.
Westbrook, J.W. et al. 2011. What makes a leaf tough? Patterns of correlated evolution
between leaf toughness traits and demographic rates among 197 shade tolerant woody
species in a Neotropical forest. The American Naturalist 177(6), 800-811.
Yao, X., et al. Exon-Primed Intron-Crossing (EPIC) Markers for Evolutionary Studies of
Ficus and Other Taxa in the Fig Family (Moraceae). Appications in Plant Science 1(10). 24
25. 3
1
2
4
5
1. South China Agricultural University
3,5. Xishuangbanna Tropical Botanical Garden
25
2. University of Science, Vietnam National University 4. University of Minnesota
Good afternoon everyone! We will talk to you today about Leaf variation in Ficus, with an evolutionary perspective
Here’s our outline: YaoXin will introduce leaf diversity and Ficus, I, Si-Jin, will present our hypothesis, Huyen will tell you what we did, Wu Wei Huan will tell you what we found, and Gao Lao will discuss our findings.
Leaves are the organs primarily responsible for all photosynthesis. However, they often exhibit remarkable diversity. For example, this picture shows the diversity of leaves in the South African genus Pelargonium. The patterns of this diversity are not well understood
Ficus is a large pantropical genus, which has more than 800 species.There is a lot of diversity in Ficus, but today, we will focus on two aspects: Life history diversity, and leaf diversity
Our first focus is life history diversity in Ficus. A lot of Figs are hemi-epiphytic; in fact, the hemi epiphytic life style is thought to have evolved four times in this genus.Individuals of hemiepiphytes star their lives on tree branches, as shown in this picture. Many studies have shown that during this stage, hemiepiphytic figs often experience a lot of water stress, because their roots are not in the ground.Eventually, the roots take hold in the ground, and the water stresses may be different.
Leaves in Ficus are very diverse: this picture shows a set of leaves collected within XTBG. We can see variation in size, shape, morphology, and texture. Today, we will focus on leaf size.
Thinking about leaf size, we might expect that because big leaves are heavier, they require more structure to hold up. Structure can come in many ways, including vein structure and lamina toughness. Today, we will focus on lamina toughness of large leaves. We can also expect that for a species to evolve large leaves, the ancestral individuals also needed to have tough leaves.
So, based on what Yao Xin has introduced about Ficus, we can have two hypotheses. First, we can expect hemiepiphytes to have evolved to deal with water stressed environments. This hypothesis leads to a prediction that hemiepiphytes will have lower leaves with lower SLA, even when grown in common gardens with terrestrial figs. We can also hypothesize that because large leaves are harder to hold up, they will be tougher. We can test this by describing the relationship between leaf size and toughness. We also expect patterns of correlated evolution between these two traits.
Our study was conducted in Xishuangbanna Tropical Botanical Garden, Fig Collection , grow under same environmental conditions common garden setting
For 3 prediction Reconstructed Ancestral trait of LA and toughness and use Phylogenetically Independent Contrasts to examined the co-evolution between them
These are our raw results, which show the variation of SLA, area,and toughness. The variation in area is huge, but SLA and toughness have less variation.
Here, we show the results of our test of prediction 1. We did not find significant difference in the leaf area and SLA of hemiepiphytic and terrestrial figs.
Here, we show the results of our test of prediction 2. Leaf size and lamina toughness do not show any significant relationship
Here, we show the results of our test of Prediction 3. This figure shows the estimates of area and toughness across the phylogeny. A dark blue color indicates that leaves are smaller or weaker; red indicate larger or stronger leaves. These two boxes seem to suggest that the patterns of trait evolution are not exactly similar.To statistically test whether the patterns of leaf area evolution and toughness are related, we calculated the PICs of leaf area and toughness. PICs are related to the rate of trait evolution across the phylogeny.If the patterns of leaf area change and toughness change are related, we will expect a significant relationship between the PICs of leaf area and the PICs of toughness.
Here is the graph of Area PICs and Toughness PICs. We did not find any significant relationship.
Our first prediction, that hemiepiphytic figs have smaller leaves with lower SLA compared to terrestrial figs, was not supported. This is in contrast to many other studies that have found this relationship; however, our study was uniquely conducted in a common garden setting. This suggests that environmental factors are driving the differences observed in nature. Although hemiepiphytes do not appear to be biologically predisposed to having leaves adapted for stress, they may have evolved other mechanisms to cope with water stress. For example, xylem water conductivity, and veins architecture may be different between hemiepiphytes and terresrials.
Our second prediction, that larger leaves need to be stronger to be held up against gravity, was not supported. It is possible that the large leaves are held up primarily to the architecture of their veins and petioles, which were not considered in our study.We also found no support for our third prediction that leaf size and toughness have undergone correlated evolution. This makes sense in light of prediction 2, because the two traits are not correlated at the tips of the phylogeny, so they are unlikely to be correlated in their evoutionary histories. Before we propose some directions for future research, we would like to acknowledge some limitations of our study.
First off, our sampling intensity might not have accounted for intraspecific variation in the measured leaf traits, so we may not have approximated the true species means. Second, our test of Hypothesis I was unbalanced, as we had only 8 hemiepiphytic and 22 epiphytic fig species.And finally, all of our tests that involved using the phylogeny were limited because the Ficus phylogeny is not completely resolved. Our methods are sensitive to the toplogy and branch lengths of the tree, so they may change with any major change in the ficus phylogeny.
And now, we would like to offer some potential avenues of research. First off, because leaves are the organs that harvest all light energy into chemical energy, we think that it is very worthwhile to study their evolutionary patterns, which are not currently well understood.