Candidacy exams

Archive of questions asked by Dr. Bahlai for PhD Candidacy exams

Student 1

Student specializes in biogeochemistry, nutrient cycing, microbiology and functional ecology. Bahlai was the examiner in population and community ecology, and functional ecology. Student was assigned 6 papers and a textbook chapter on biodiversity and function

Written exam questions

1. Discuss the links between ecosystem service and ecosystem function. How does biodiversity influence service and function? Provide an illustrative example that distinguishes between these terms and related processes in an ecosystem that is familiar to you. Illustrate your answer with a conceptual diagram.

2. In your assigned readings, we’ve focused on the work of a single scientist, Dr. Elena Bennett, as a way to illustrate how a scientist’s research program can arise around a set of related questions. What is/are the core question(s) driving Dr. Bennett’s research program? For each of the six papers I assigned you, outline the paper’s main questions/objectives, its core findings or conclusions, and discuss how this fits into Dr. Bennett’s core research direction. Do you think Dr. Bennett’s core research program has changed over time? Why or why not?

3. Despite being one of the most prominent thinkers on the concepts of biodiversity drivers of ecosystem function and ecosystem service of our time, Dr. Elena Bennett of McGill University does not yet have a Wikipedia page. Given what you know now about the field and Dr. Bennett’s work, write a brief Wikipedia article. You can use this article, on prominent Kent State epidemiologist Tara Smith, as a template or as inspiration: https://en.wikipedia.org/wiki/Tara_Smith_(scientist)

Update: A wikipedia page for Dr. Bennett was created by another user a couple months after this exam in September 2019- guess this was on a few people's minds!

Oral Exam Questions

1. Some authors treat ecosystem services and functions as very different things, and others use the terms almost interchangably. What do you think? As you did your readings, did you notice any patterns in how different authors used the terminology?

2. I thought it was interesting that you used sandstone filtering pollutants out of water as an example of a provisioning function. As an organismal person, I usually think of biotic examples first. So this got me thinking- are abiotic processes ecosystem functions, or would you classify them as geochemical processes? or are they both? Is there a difference?

3. You mentioned that ecosystem functions 'maintain quality and viability ' of an ecosystem and I want to dig into that a bit- what do you mean by 'quality'? What about 'viability'? Are there processes and functions that can undermine quality and viability?

4. As a followup to my first question, can you think of other examples where differences in geography or dicipline have led scientists to come up with multiple definitions for the same terminology? What about multiple terms for very similar concepts?

5. What are the ecosystem functions and services that you study in your work? Are any of them synergistic? Are there tradeoffs between any of the ecosystem services within your study system?

6. Say you had unlimited resources- time, money, technology- how would that change your research plan? And once you're done your study, given all this knowledge and power- what would you manipulate in your system to restore it to its ideal function?

Student 2

Student specializes in ecosystem services, insect functional ecology, biodiversity and habitat structure. Student elected to do a 'proposal style' candidacy exam and wrote a proposal based on NSF's (now defunct) DDIG guidelines. Proposal examined landscape and environmental drivers of dispersal patterns of two different groups of pollinating insects in small cities. These questions were asked during the oral defense of this proposal

1. Why study small cities? From both an ecological and human perspective?

2. If NSF decided to fund this project but cut out the budget for all the materials, what would you do? Are there different (lower tech, cheaper?) experimental techniques you could use?

3. Why is dispersal important? Why not just study resident organisms?

4. Say you find a positive relationship with impervious surface and number of syrphids in Bowling Green, but a negative relationship in Kent. What does this mean? What would you do to reconcile the two apparently opposing patterns?

5. Do you think cities are important for conservation of rare species? What about ecosystem services? Are there tradeoffs between rare species conservation and ecosystem services?

6. What is a disturbance? What is the intermediate disturbance hypothesis?

7. Why do you think syrphids might respond less negatively to disturbance than bees?

8. Why are species with lower dispersal ability more vulnerable in fragmented habitats?

9. What scale will you measure NDVI and impervious surface at? Why not another scale?

10. I know there’s a space limitation, but I’d like to see the collection methods for measuring dispersal developed more. How far away would you go? How many sites would you collect from? How would you consider directionality in the model? How would you calibrate- so say flying a certain distance makes the protein ‘wear off’ more- is there a way of quantifying the marking or is it presence/absence?

11. Why would specialists have lower dispersal ability?

12. Does the presence of insect DNA on a flower measure the flower’s attractiveness? How would you measure attractiveness?

Student 3

Student specializes in trophic interactions, grazing mammals, foraging theory and habitat structure. Student elected to do a 'proposal style' candidacy exam and wrote a proposal based on NSF's (now defunct) DDIG guidelines. Proposal examined sompetitive interactions between bighorn sheep and mountaing goats under changing ranges in the Rocky Mountains. These questions were asked during the oral defense of this proposal

1. You used the terms introduced, non-native, and invader. What do each of these terms mean? Are these terms interchangeable?

2. What affects niche partitioning? How do you decide which traits are associated with niche partitioning, and which traits are simply natural variation? Is there a way to test this?

3. You focused a lot on the competition aspects of invasion- so the impacts of a new species on a functionally similar species occupying that niche. What other effects might a new species have in the environment?

4. What is an optimal habitat?

5. Where do you expect competition to occur between these two species? Why? Would measuring the reproductive success of females and the mortality of young get at each of these factors? What other fitness measures might be affected? If you had more money and time, what other things would you measure?

6. There was a bit of hand-waving in the broader impacts that I’d like to see developed- who are the local cultures that hunt these animals? How will your work help them?

7. Would mountain goat range expansion have happened without human activities?

8. This is sort of a bigger philosophical question. At one point you wrote: “I shall also analyze if competition is in fact a mechanism through which mountain goats are negatively affecting bighorn-sheep populations.” So what do you mean by “a mechanism?” how strong does an effect need to be for it to count? What if there are other things going on?

9. Can you explain your conceptual figure more? What predictions are you making?

10. You used the phrase “Threat of competition”- what does that mean? How does it differ from “competition”? Could you design an experiment to discern between competition and the threat of competition?

11. So let’s talk a bit about population viability analysis- you mention that this family of approaches generally requires ‘precise variables that are species specific’- how much variation is tolerable? How do you decide what information to include in a model like this? Say you had two values from the literature- let’s say it’s fecundity per female. One study of 1200 individuals found 3+/-4 offspring per female, another study of 13 individuals found 4+/-0.2 offspring per female. Which value would you use in your model? How would using each change your model’s predictions?

12. You mention numerous benefits of using long-term data to characterize natural variation in the community. What about space-for-time substitutions? Can you use spatial variation to get the information you need?

13. Why will you resample your data for your G-test on behavioral interactions?

14. What kind of music will be playing when you jump out of your helicopter to wrestle a mountain goat?

15. So this is a big project. With a big budget. What approach would you take if NSF said YES, do it, but we can only give you $10,000? Would you blow it all on one helicopter ride?

16. You’ll consider undergraduates from all backgrounds as field assistants, but will you make any specific efforts to recruit under-represented minorities? How?

Student 4

Student specializes in distribution, abundance, phenology and natural history of odonates, the dragonflies and damselflies. For their classic style exam, I focuses on quantiative ecology and biodiversity data science. I provided eight papers in issues adjacent to their direct research areas and for the student's written assignment, they wrote in-depth reflections of each. The questioning focussed on probing some of the statements made in these reflections, integrating some of the new information with current events

1. The Beck paper discussed spatial biases in species distribution data in the GBIF database. Where does GBIF data come from? Why do you think they focused on one butterfly species? Do you think they would have had a different result if they used another taxon? What taxa do you think are most likely to lead to different conclusions?

2. I’m currently working with some colleagues on the distribution of ladybeetle species in Ohio over the last century. We’re using all the Ohio-geolocated data from museums in Ohio and adjacent states. What biases should I be looking for? Can you make any predictions about the distribution of the raw data? What sort of corrections should I think about when trying to map the relative distribution of these ladybeetle species?

3. In the Termaat paper, they found that dragonfly species generally increased, rather than decreased their ranges over the last 30 years. Let’s talk about that in the context of the (Hutchinsonian) niche concept- did the niche of these dragonflies change? What about the minority of species that conserved their range- did their niches change? How does the concept of species range differ from the concept of a species’ niche?

4. You noted in your answer to the Richter paper prompt that the phenology of their focal dragonfly taxa seemed to respond to both photoperiod and temperature cues. What biological reason might a species’ phenology respond to photoperiod? What about temperature? How would you design an experiment to tease out the relative importance of these two cues? What would you need to do that work? I liked your comment about egg-overwintering vs niad-overwintering odonates- do you have any predictions about how taxa employing each of those life history strategies might respond?

5. The Reutter paper explored habitat suitability for three European mice species using museum specimens. My main question here is how did their approach differ for this vertebrate problem compared to the invertebrate distribution models you’re more focused on? You also had an interesting question about how the timescales of the museum data used affect the outcome- can you explain this a bit more? Why might this be a factor to consider?

6. The Araujo (2006) and Dormann (2018) papers are conceptually very similar- but Dormann was written 12 years later and doesn’t, in fact, cite the Araujo paper. Was this an oversight? Should Dormann have cited Arajuo?

7. About 10 years ago the concept of including biotic interactions in species distribution models really started hitting the literature hard. Why was that? So, for example, the Wisz article was one of the big position pieces that came out on this subject. What do they mean by “biotic interaction” and why are they important? I personally became aware of the ‘biotic interaction’ issue when a bioclimatic envelope model paper came out that warned of potential future distributions of soybean aphid in the Canadian prairies. Can you speculate about what made me skeptical about that paper?

8. Your question for the authors on the Wisz paper pointed to the intensive data needs for incorporating biotic interaction in species distribution modelling. But what role do you think systemic expertise plays in this? Basically- what role do domain experts play in the development of these models? What roles do modellers play?

9. The Flenner paper explored the idea of community change in terms of environmental drivers, and your question to the authors was excellent. Do you think their approach to their analysis was appropriate? Should Anisopterans be modeled differently, with regards to scale and specific variables, than zygopterans? Why or why not?

10. I just want to talk about the Araujo and Naimi preprint. Wow, eh? But also, are there biological reasons why their results might be at best, hasty?