Hypothesis Generation Notes (Please read before Lecture on Aug. 23 rd ) I. There are three main approaches to the study of ecology.

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1 Field Ecology 2016 Dr. Burford Reiskind Hypothesis Generation Notes (Please read before Lecture on Aug. 23 rd ) I. There are three main approaches to the study of ecology. The bulk of what we will do in this course is A and C, but we will use a type of model to help us define our study. The three areas are loosely categorized as the following: A. Observational, descriptive studies, Natural history studies a. As we said on the first day this was the mainstay of ecological studies in the past. b. Goal is to gain a general knowledge about an ecological process, a disease progression, etc. etc. c. Typically we use inductive reasoning, building support for our conclusions as the example we used in class about cells in plants and animals d. Observational studies are just as important today as in the past. In some cases this is all we can do to understand ecological processes, because some systems or processes cannot be experimentally manipulated, as they occur at scales that are large or we cannot replicate. Observational studies often are the best way to gain ecological understanding. e. Observational studies are also important, because they help us better understand the natural systems and provide a context for further investigation of what might be driving the patterns we study. They help inform future experimental studies. f. One of the big issues is these observational studies are often correlative studies. Therefore, while it might support associations, the cause may still be elusive. This is why ecologists get really warm and fuzzy about the experimental approach. g. Examples of observational studies species descriptions, behavioral observations, biological surveys, population genetic structure, the list goes on and many, if not all, of the studies we will do in the class will be observational studies. B. Modeling a. We will talk more about this later in the course, but understanding population dynamics (think back to Bio 360) and life- history strategies, population genetic patterns, species range movements, population viability analyses, mark- and- recapture are all examples of ecological modeling studies. C. Experimental Manipulation (in the field, in the lab, small- scale and large scale) a. Experimenter controls one or at most a few variables 1

2 If the experiment is set up correctly and one factor is varied, responses in the dependent variable can be attributed to the manipulated variable. b. Powerful approach for establishing causality c. Often there are treatments, and we have to make sure that we randomly assign treatments to each replicate. We will talk more about this when we talk about experimental and sample design in the following weeks. d. We conduct manipulative experiments at a variety of scales, microcosms, mesocosms, and out in the field. II. How to we pick a question for an observational or experimental study? A. General Considerations: a. First, can it be answered by the scientific method? Remember we can only test natural phenomenon. For example, lightning is produced by Zeus when he is in a super bad mood or that Spiderman is more powerful than Superman are questions we just can t answer, even if we believe they are true! My vote is with Spidey! b. Is it too broad? Is it too specific? Examples of too broad: what is sunlight; do plants require water to grow; what is gravity; is there a difference between forest types Initially, especially when we haven t had much time to make observations or are not well versed in the system, we generate very broad questions like those above. It takes a little while to get to what I call the Goldilocks Hypothesis, neither too broad nor too narrow! Occasionally we are too specific to reasonably measure or to generalize. For example, if we think back to a question about a dead fern in your dorm room and water and plant growth, you could hypothesize that ½ a cup of water every other day is required for the plant in your dorm room. You would test that, but not a range of amounts of water, and you would only be testing the plant in your room. We will talk more about this example in class. c. Goldilocks Hypotheses. Neither too broad nor too specific. Following from above better questions are: Is sunlight required for germination of a seed? How does gravity affect plant growth and are there differences in support structures throughout the plant that are related to differences in gravitational forces (top to bottom)? Is there a difference in spider density in different forest types? 2

3 d. Avoid being a jackrabbit or a perfectionist A perfectionist is never happy with their questions; you have to try a few bad ones to get to the best one. Don t be scared to dive in. Jackrabbits never follow anything through, they hop around to question after question, lots of great questions, but they just don t settle. Try to be somewhere between these two extremes. e. What are you interested in? Plants? Animals? Processes? Etc. etc. Make sure you pick a topic you re actually interested in. This seems obvious, but sometimes it s hard to know what is interesting. Think a little bit about what you ll be doing and where you ll be if you study this question, process, or species. Is it in a location that works for you? Often times studies that don t sound interesting, turn out to be fascinating, so don t overthink this too much. g. Is it feasible to answer the question? Can you actually answer this question in the time allotted? If it requires observing a species over multiple seasons, probably not a good question for this course. If it requires a large geographic area to sample, it is likely not feasible. In most cases this is going to be a limitation to your independent research. B. The process of picking a question a. All well- thought out questions start with observations As we have already talked about, as we did with the treehole exercise, and will do throughout the course, a little time spent making observations will help produce well- thought out questions. The basis of ecological studies is patterns of change over space and time, i.e. variation. If there is no variation observed it is difficult to propose an explanation. This is what you want to observe. Generate a list of observation and potential questions in your Field Notebook e. Research previous studies addressing this question (if at all); talk to researchers working on this or similar questions or in a similar system. This helps you identify potential areas that haven t been addressed already, helps you find your angles on the overall question or what your specific interest is. You can always talk to your instructors too, they may know people or literature that would be helpful. Asking questions helps you get to the best questions. f. Think about underlying mechanisms and make a list We will work through examples in class as well, but we have already made a short list of mechanisms responsible for species diversity and abundance in the treehole observational study. 3

4 Ask questions such as how variable is the trait, and is there a spatial or temporal pattern to this variation? What factors correlate with the variation that you observed? You want to have a list of potential mechanisms that you can narrow down to address one or a couple of these mechanisms, which will help direct the sampling you need to do to address those questions. g. Given the above how would you test these mechanisms that are causing the observed natural phenomenon? This takes a little more thinking. Back to the dead fern in your dorm room, can you make a list of potential factors that may have killed that fern based on things you know the fern may need to survive. III. Defining variables and building a hypothesis model (direct and indirect effects) in ecology. In this course we will use the independent and dependent variables in the formal hypothesis and models A. Independent variables Is the variable that influences other variables, often this(these) is(are) the one(s) that the scientist is changing in an experimental study. There are many examples of independent variables that we will talk about. Going back the fern in your dorm example, an independent variable could be water. B. Dependent variables Is the variable that is influenced (=response variable) by the independent variable. Variance in the independent variable influences variation in the dependent variable. In the plant example, the dependent variable(s) would be growth or survival. C. Controls These are the variables that could influence the outcome of the test if not kept constant or if not accounted for. In previous courses and here, there are many examples of controls. For example, in a predator exclusion experiment, we need to deal with a cage effects. In this example, we would put a cage out that allowed organisms to go in and out as our control plot. D. Relationships between the variables Direct effects the variable has a direct effect on another variable Indirect effects the variable has an indirect effect on another variable. This is often via influence on another variable that directly affects the variable of interest. E. Using models to show the variables We will use models to visualize the variables and relationships between the variables. The goal is to produce a model that provides a simple, but realistic, visualization of the hypothesis. Model of the fern experiment: 4

5 Water (independent) + Direct effect Plant growth (dependent) + Direct effect Sunlight (independent) F. The symbolic hypothesis Another approach that is very helpful and helps organize how you ll refine your hypothesis into the components you want to test. This is something that you might want to put into your proposal (along with the model above). Here s an example: You observe a greater number of male professors in your biology department. You wonder whether there is a statistically significant greater number of men than women. Your hypothesis: there are a significantly greater number of males than females in a biology department. Your null hypothesis is there is no difference in the number of females than males. If this hypothesis is true you predict that there will be a greater number of men that walk by a classroom door than females over a 5- hour period in the department. Given the above, here is how to represent this symbolically: H0: # men = # women H1: # men > # women IV. Defining the universe of interest what is the spatial and temporal scale of your question of interest. Defining the scale determines sampling design and your ability to make inferences. A. Space Local, regional. Continental, global B. Time Now, seasonal, annual, interannual, decadal, millennial C. Once you decide on the scale you can then make sure you take samples that represent this scale. For example if you want to know the species diversity and abundances of the Yates Mill Pond, you would need to think about how many samples you need to capture that information. How about if you were going to look at fish diversity and abundances from the NE to the SE of North America. How many ponds would you sample in each region? We will talk more about this as we talk about experimental and sampling design. V. Hypothesis to predictions Make sure your hypothesis is in present tense and incorporates your independent and dependent variables 5

6 If, then statements help you get from your hypothesis to your predictions. IF this hypothesis is true, THEN I predict the following will happen. Note the first part is in present tense and the second part after THEN is in future tense. 6