Investigating Symbiosis in Carnivorous Pitcher Plants

Investigating Symbiosis
in Carnivorous Pitcher Plants
Leonora Bittleston
Pierce and Pringle Labs
Organismic and Evolutionary Biology
Harvard University
Roadmap for the evening
1.  Evolution of carnivorous plants
2.  Symbiosis in pitcher plants
My research here 3.  Convergence in pitcher plant communities
4.  Carnivorous plants and global change
What is a carnivorous plant?
Images: N. Elhardt,Veledan via Wikimedia commons, BBC,Vincent et al. (2011), Proc Roy Soc B., L. Bittleston
What is a carnivorous plant?
Images: N. Elhardt,Veledan via Wikimedia commons, BBC,Vincent et al. (2011), Proc Roy Soc B., L. Bittleston
What is a carnivorous plant?
Images: N. Elhardt,Veledan via Wikimedia commons, BBC,Vincent et al. (2011), Proc Roy Soc B., L. Bittleston
What is a carnivorous plant?
•  Traps prey
•  Makes digestive enzymes
•  Gets nutrients from prey
Images: T. Shafee, G. Robson via Wikimedia commons
Plant nutrients
•  Plants get energy and basic building blocks
from sunlight and CO2
•  Still need nitrogen, phosphorus, potassium
to grow Images: Cjp24, G. Robson via Wikimedia commons
Where do you find carnivorous plants?
•  On all continents except Antartica, in
places with:
Poor soils
é water
é sunlight
Images: open clip art via Wikimedia commons
Where do you find carnivorous plants?
Images: G. Robson & open clip art via Wikimedia commons
Venus flytrap
1769: John Ellis
wrote to Carl Linnaeus
“…against the order
of nature as willed by
God”
Image: The Hunt Institute via Wikimedia Commons
Charles Darwin
Insectivorous Plants,1875
Image: public domain
Convergent evolution
The independent evolution of similar features
in species from different lineages
Convergent evolution
Images: Pearson via Wikimedia commons
Carnivory in plants
Has evolved separately at least 5 times!
…and the pitcher plant form has evolved
3 different times!
Images: L. Bittleston; D. Barthel, S. Peulen, & M. Manske via Wikimedia commons
Carnivorous Pitcher Plants
Sarraceniaceae
N. and S. America
Nepenthaceae
Southeast Asia
Images: L. Bittleston; D. Barthel via Wikimedia commons
Cephalotaceae
Australia
Summary for Part I
•  Carnivorous plants get nutrients from prey
•  Grow in wet, sunny, low-nutrient places
•  Studied even before Darwin’s time
•  Plants evolved carnivory at least 5 times
•  Pitcher plants evolved 3 separate times
Questions?
Photos: L. Bittleston
Roadmap for the evening
1.  Evolution of carnivorous plants
2.  Symbiosis in pitcher plants
3.  Convergence in pitcher plant communities
4.  Carnivorous plants and global change
Evolution
•  Brutal process of competition
•  Also: large evolutionary advances can happen
when organisms cooperate Images: L. Bittleston; D. Barthel via Wikimedia commons
Symbiosis
•  Commonly: positive interactions
•  Originally: prolonged close interactions
sym = ‘together’ + bios = ‘life’
•  Now most scientists use second meaning:
could be positive, negative, or neutral
Some pitcher plants have positive relationships with animals
Images: L. Bittleston; Greenwood et al (2011) & Bazille et al (2012) PLoS ONE, H. Breuer via Wikimedia commons
Nepenthes
community
Gall midge
Mosquito larva
Other
organisms?
Mite
Scuttle fly larva
?
Bacteria and
fungal yeasts
Images: M. Lim, L. Strominger and L. Bittleston
Insect prey (mostly ants) and debris
Images: Adlassnig, et al. (2011) Annals of Botany, NIDDK Image Library, NIH
What organisms live in Nepenthes pitcher plants?
What organisms live in Nepenthes pitcher plants?
Image: L. Bittleston
• 
• 
• 
• 
• 
Collect fluid in sterile tubes
Measure volume and pH Add preservative
Count insects
Extract DNA
Image: K. Gilbert
DNA sequencing of the whole community
•  One drop of pitcher water has thousands
of species of bacteria
•  Snippets of DNA allow us to find out what
is there
Image: M. Ströck via Wikimedia commons
What organisms live in Nepenthes pitcher plants?
•  Most species have not been described yet
–  Bacteria: mostly ones that like acidic conditions
–  Fungi: mostly yeasts
–  Aquatic insects: mostly mosquitoes, mites, flies
–  Algae, insect parasites and others
Images: L. Bittleston
Symbiosis in pitcher plants
•  Are the organisms inside helping or harming the
plants?
Image: L. Bittleston
Summary for Part 2
• 
Evolution happens through cooperation as well as
competition
• 
Symbiosis: prolonged close interactions (positive,
negative or neutral)
• 
A food web, or community, lives in pitcher plants
• 
Most of the organisms are unknown
• 
…and we still don’t know what they are doing
Questions?
Intermission
Images: L. Bittleston
Roadmap for the evening
1.  Evolution of carnivorous plants
2.  Symbiosis in pitcher plants
3.  Convergence in pitcher plant communities
4.  Carnivorous plants and global change
Convergent evolution
Convergent interactions?
Images: Pearson, via Wikimedia commons
Convergent interactions
This interaction has evolved separately at least 14 times! Bittleston, Pierce, Ellison & Pringle, 2014 (in preparation).
Convergent interactions
Sarracenia
Images: L. Bittleston
Nepenthes
Convergent interactions
Protozoa
& rotifers
Protozoa
& rotifers
Fungi & bacteria
Fungi & bacteria
Sarracenia
Images: L. Bittleston
Nepenthes
Sarracenia
N. America
Images: L. Bittleston
Nepenthes
Southeast Asia
Bacterial communities from pitcher plants on opposite sides of
the world are more similar than those from surroundings
Images: clip art, Hansen via Wikimedia commons; L. Bittleston
Mosquito larvae in pitcher plants
Sarracenia
1.00
Proportion of pitchers with W. smithii
0.90
0.80
0.70
Nepenthes
0.60
0.50
0.40
0.30
Controls
0.20
0.10
10
5
6
12
Sp bog
Sp pot
Nb
Na
10
10
0.00
Tube Tube + p
The main pitcher plant yeast is found
inside the pitcher plant mosquito
Images: L. Bittleston
Conclusions
•  Pitcher plant communities may be convergent, just like the
pitchers
•  This may extend to other systems where similar
pressures cause similar organisms to interact with each
other
Summary for Part 3
• 
Convergent evolution can apply to species interactions • 
Bacterial communities in pitcher plants are more similar
than those from the surroundings
• 
Local pitcher plant mosquitoes colonize foreign pitcher
plants
• 
Communities may follow the convergence of their hosts
Roadmap for the evening
1.  Evolution of carnivorous plants
2.  Symbiosis in pitcher plants
3.  Convergence in pitcher plant communities
4.  Carnivorous plants and global change
Global change
Reactive nitrogen released into air and soil
Images: public domain, Cjp24 via Wikimedia commons Nitrogen is increasing
Too much nitrogen is bad
Pitchers stop forming
Carnivorous plants
lose their advantage
in their habitats
Images: Ellison and Gotelli (2002) PNAS
Habitat destruction
Images: L. Bittleston, clip art
Conservation
Images: L. Bittleston; N. Elhardt,Veledan via Wikimedia commons Thank you!
SITN would like to acknowledge the following
organizations for their generous support.
Harvard Medical School
Office of Communications and External Relations
Division of Medical Sciences
The Harvard Graduate School of Arts and Sciences (GSAS)
The Harvard Graduate Student Council (GSC)
The Harvard Biomedical Graduate Students Organization (BGSO)
The Harvard/MIT COOP