Plant pathogens and tropical tree diversity
Lead Research Organisation:
University of Oxford
Department Name: Zoology
Abstract
At least half of all the earth's species of plants and animals live in tropical forests, and there is considerable interest in the ecological processes maintaining this extraordinary diversity. Explaining the high diversity of tropical trees is a particular challenge, because most plant species use very similar resources: just one or a few highly competitive species might be expected to dominate the forest, rather than the hundreds of species per hectare that are often observed. If we can explain the high diversity of tropical trees, then the high diversity of other taxa in tropical forests may follow. Recently, evidence has been growing that high plant diversity in tropical forests arises because of strong density-dependent seed and seedling mortality. In other words, seeds and seedlings are more likely to die when close to their parent tree and close to other seedlings of the same species. This puts locally rare plant species at an advantage, preventing any one species from reaching high abundance. It is widely suspected that fungus-like plant pathogens are responsible for seedling density-dependence. However, the evidence for their role in maintaining high plant diversity in tropical forests is largely circumstantial, and their effects on the wider structure of tropical forest communities have not been explored fully . We will test the hypothesis that plant pathogens maintain high plant diversity at our study site in Belize, Central America. We will address five key outstanding questions: (i) How widespread is pathogen mediated density-dependence? For pathogens to play an important structuring role in tropical forest communities, their effects must be widespread. Exclusion experiments using selective fungicides will reveal whether pathogens are driving density-dependent mortality. (ii) Are pathogens specialist or generalist? Density dependence is expected to have the strongest diversity-enhancing role when natural enemies show high host specificity. Molecular and experimental approaches will be used to assess the specificity of pathogen species and strains isolated from seedlings of individual tropical tree species. (iii) Do pathogens mediate indirect interactions among plant species? We will assess the extent to which pathogens are shared between pairs of plant species, and investigate the community-wide impacts of shared parasitism. (v) How do pathogens affect the relationship between host density and mortality? We will determine whether the the relationship between density and mortality is of a form likely to promote plant diversity, and we will determine the relative importance of density and distance from parent tree in influencing mortality. (iv) Does mortality from pathogens increase diversity? We will carry out the first experimental test of the hypothesis that pathogens promote plant diversity by comparing the diversity of the seed rain with the diversity of new seedlings in fungicide-treated and untreated plots.
Publications
Bagchi R
(2010)
Testing the Janzen-Connell mechanism: pathogens cause overcompensating density dependence in a tropical tree.
in Ecology letters
Bagchi R
(2014)
Pathogens and insect herbivores drive rainforest plant diversity and composition.
in Nature
Lawson C
(2012)
Dung Beetles Reduce Clustering of Tropical Tree Seedlings
in Biotropica
Lewis O
(2008)
Insect seed predators and environmental change
in Journal of Applied Ecology
Swinfield T
(2012)
Consequences of changing rainfall for fungal pathogen-induced mortality in tropical tree seedlings.
in Ecology and evolution
Description | We found that pathogenic fungi and insect herbivores play a role in maintaining and structuring tropical plant diversity. |
Exploitation Route | Our work has implications for forest restoration. To restore diverse ecosystems like rainforests, simply planting trees may not be enough - conservationists may need to restore soil fungi and other microbes too. If the mechanisms we identify are sensitive to changes in the climate then our results also suggest that anthropogenic climate change may have hitherto unexpected consequences for the diversity of plants and the organisms that depend on them. These possibilities warrant further investigation. |
Sectors | Agriculture Food and Drink Environment |
URL | http://www.ox.ac.uk/research/research-impact/discovering-rainforest-%E2%80%98diversity-police%E2%80%99 |
Description | Follow-up funding bid - cross-gradient fungal specificity |
Organisation | Smithsonian Institution |
Department | Smithsonian Tropical Research Institute |
Country | Panama |
Sector | Academic/University |
PI Contribution | Collaborative funding application for follow-up project to NSF-DEB/NERC. Research design and preparation of funding application. |
Collaborator Contribution | Research design and preparation of funding application. |
Impact | None as yet |
Start Year | 2015 |
Description | Follow-up funding bid - cross-gradient fungal specificity |
Organisation | University of California, Santa Cruz |
Department | Department of Environmental Studies |
Country | United States |
Sector | Academic/University |
PI Contribution | Collaborative funding application for follow-up project to NSF-DEB/NERC. Research design and preparation of funding application. |
Collaborator Contribution | Research design and preparation of funding application. |
Impact | None as yet |
Start Year | 2015 |
Description | Follow-up funding bid - cross-gradient fungal specificity |
Organisation | University of Connecticut |
Department | Department of Ecology and Evolutionary Biology |
Country | United States |
Sector | Academic/University |
PI Contribution | Collaborative funding application for follow-up project to NSF-DEB/NERC. Research design and preparation of funding application. |
Collaborator Contribution | Research design and preparation of funding application. |
Impact | None as yet |
Start Year | 2015 |
Description | Ilmington School visit and talk 2019 |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | Owen Lewis gave a 30 minute talk and Q&A about tropical rainforests, climate change, deforestation and biodiversity with 55 Key Stage 2 children and their teachers at Ilmington Primary School, Warwickshire. |
Year(s) Of Engagement Activity | 2019 |
Description | Invited Plenary Talk at Gordon Conference on Plant-Herbivore Interactions |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Owen Lewis gave an invited plenary talk at the Plant-Herbivore Interaction Gordon Research Conference in Ventura, California (February 24 - March 1, 2019) on 'Plant-insect food webs in tropical forests'. |
Year(s) Of Engagement Activity | 2019 |
URL | https://www.grc.org/plant-herbivore-interaction-conference/2019/ |
Description | Invited Plenary Talk, European Conference of Tropical Ecology, Brussels 6-10 February 2017 |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other audiences |
Results and Impact | Plenary talk, focusing on the results from three NERC-funded research projects. |
Year(s) Of Engagement Activity | 2017 |
Description | Invited seminar, Liverpool University |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Postgraduate students |
Results and Impact | Invited seminar on tropical forests at the University of Liverpool, 14th February 2019. |
Year(s) Of Engagement Activity | 2019 |