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 Nepenthaceae Cephalotaceae N. and S. America Southeast Asia Australia
Images: L. Bittleston; D. Barthel via Wikimedia commons 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
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 Nepenthes
Images: L. Bittleston Convergent interactions
Protozoa Protozoa & rotifers & rotifers Fungi & bacteria Fungi & bacteria
Sarracenia Nepenthes
Images: L. Bittleston Sarracenia Nepenthes N. America Southeast Asia
Images: L. Bittleston 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
0.90
0.80 smithii 0.70 W. W. Nepenthes 0.60
0.50
0.40
0.30
0.20 Controls Proportion of pitchers with with of pitchers Proportion 0.10 10 5 6 12 10 10 0.00 Sp bog Sp pot Nb Na 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