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The impact of deforestation on an obligate ant/plant farming symbiosis

  • Full or part time
  • Application Deadline
    Friday, January 10, 2020
  • Competition Funded PhD Project (Students Worldwide)
    Competition Funded PhD Project (Students Worldwide)

Project Description

We are seeking a highly motivated PhD student to join this exciting project on the macroevolution of mutualisms. Students with background including computer science, applied mathematics and environmental science are encouraged to apply in addition to those from pure biological sciences. The scope of the project can be modified in function of the students interests and skills.
Background Deforestation driven by land conversion to agriculture is a major threat to both global biodiversity and our target of CO2 emissions. Research on the impact of deforestation has been mostly carried out with a focus on species in isolation. However, species are embedded in complex networks of species interactions, which could accelerate or slow down the impact of deforestation. How species interactions are affected by deforestation is poorly known, yet it is essential to implement effective conservation policies. Models suggest that co-extinction is the most common form of species loss, thus suggesting that obligate species interactions will be the first to go extinct [1-3]. The present project proposes to tackle this by investigating the impact of deforestation on the obligate farming mutualism involving ants farming plants in Fiji. This obligate interaction involves an ant species (Philidris nagasau) that cultivates epiphytic plants (Squamellaria) on Fiji [4, 5]. Recent research has shown that the ants mediate environmental conditions to increase the yield of their plant crops. In particular, they plant Squamellaria crops in high light environments on the canopy [6]. Because deforestation affects drastically light levels, we now want to investigate its consequences on the mutualism. Does deforestation affect the farming behaviour of ants? How are ant and plant colony structures impacted? Is there a nitrogen limitation in the system, and if so, is it pushing the mutualism to the edge? Can we detect fast evolutionary changes in 30 years of deforestation? These are the kind of questions that we want to answer. This project will thus advance our understanding of obligate mutualisms, and our analyses will allow to trace the impact of human activity on complex multi-species behaviours, with the ultimate goal to implement new conservation policies in one of the world’s biodiversity hotspot.

Aims The student will conduct extensive fieldwork on the Fijian island of Taveuni, where deforestation has been under way for three decades and its pace is well-documented. The student will perform high-resolution mapping of the mutualism across the Fijian island of Taveuni, explore various aspects of its functioning in non-logged (protected) versus logged areas using field observations and experiments and collect samples for DNA analysis. The farming behaviour will be evaluated by fine-scale mapping of colonies in logged vs. non-logged forests, and a number of manipulative assays (e.g. cafeteria-type experiments) to assess seed preference and planting sites selection in logged vs. non-logged forest will be performed. Nitrogen levels will be compared in plants and ant colonies across the logging gradient using isotope-ratio mass spectrometry (IR-MS); photosynthetic efficiency and plant stress will be measured across the gradient using non-destructive spectroscopic approaches; transcriptomics and population genomics will compare key traits across the logging gradient to test the hypothesis that decades of logging have resulted in fast evolutionary change in the symbiosis – notably with regards to nitrogen cycling.

Methodology This project will use (i) field-based GIS monitoring, (ii) spatial modelling, (iii) field experiments, (iv) genomics (transcriptomics and targeted-gene sequencing [hybrid capture]) to seek changes in key farming traits linked to deforestation in the past decades.

Timetable of Activities Year 1: Complete the field-based GIS monitoring and field observations and experiments. Year 2: Build the spatial models from the field data and measure various parameters and traits of the symbiotic system. Start genomic analyses using samples collected in Year 1. Year 3: Finish genomic analyses and write up thesis.

Novelty Rainforest is destroyed at an unprecedented rate, imperilling both biodiversity and climate change. The impact of rainforest destruction has mostly been studied in the lens of species in isolation, yet species are embedded in complex networks of species interactions. Models predict that obligate interactions should be the first to go extinct, but how they are impacted by human activity such as deforestation is unknown. This project thus addresses a major gap in the literature, with high potential for direct socio-economic impact. As a result, I anticipate that this will result in several high-profile publications.
Student Training The student will receive training in (1) field monitoring, data collection and field experiment design; (2) spatial modelling using GIS software and R; (3) genomic analyses (transcriptome assembly and analysis; population genomics).

Funding Notes

Funded by a Chinese Council Scholarship, this project is in competition with others for funding. . Success will depend on the quality of applications received, relative to those for competing projects. Potential applicants should contact the supervisor (), with a CV and covering letter, detailing your reasons for applying for the project.


1. Koh et al. 2004. Science 305: 1632-1634. 2 Dunn et al. 2009. Proceedings B 276: 3037-3045. 3 Chomicki et al. 2019. TREE 34: 698-711. 4. Chomicki G. & Renner S.S. (2016). Nature Plants 2: 16181. 5. Chomicki G. & Renner S.S. (2017). PNAS 114: 3951-3956. 6 Chomicki G. et al. PNAS (In revision).

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