The aim of these exercises is to help you make the link between verbal descriptions of sample collection and the appropriate linear model for analysis.
Below you will find brief descriptions of several research studies. For each study, you should be able to answer the following questions:
1. What is the biological question? Think about the plausible cause-effect relationship between variables.
2. What is/are the response variable(s)?
3. What is the predictor variable?
4. Write a linear model for this data set
5. What link function would you use?
6. What estimation method would you use?
Le Boeuf et al. (2000) examined the foraging behaviour of northern elephant seals (Mirounga angustirostris) that breed along the west coast of Mexico and the USA. They attached platform satellite transmitter terminals (PTTs) to 22 male seals and recorded, for each seal, the distance (km) to its main feeding area offshore and the amount of time (duration in days) it spent at the feeding area.
Relationships between species richness and habitat area has long been of interest to ecologists. Peake and Quinn (1993) investigated the relationship between the number of individuals and number of species of invertebrates living in amongst clumps of mussels on a rocky intertidal shore and the area of those mussel clumps.
Vosteen, Gershenzon, and Kunert (2016) examined patterns of production of honeydew by different races of pea aphids (Acyrthosiphon pisum) and how that attracts ovipositioning hoverflies (Episyrphus balteatus) to create enemy-free space for the aphids. They measured honeydew production (mg) over 24 hours by three races of aphids (representing the native hosts they were collected from: Triflolium, Pisum, Medicago races) on plants of their native hosts and also the universal host plant Vicia faba in a climate chamber. There were six combinations of aphid race and host (native vs universal) plant that Vosteen et al (2016) treated as a single factor.
Binning, Roche, and Layton (2013) studied the effect of ectoparasitic isopods (*Anilocra nemipteri*) on the swimming ability of a tropical species of bream (*Scolopsis bilineatus*). They collected 18 unparasitized and 20 parasitized fish from Lizard Island on the Great Barrier Reef and created four treatment groups in the laboratory: eight unparasitized fish, 10 parasitized fish, 10 parasitized fish that had the parasites removed, and ten unparasitized fish that had model parasites made of plastic added. They recorded the swimming speed (body lengths per second) and oxygen consumption (mgO~2~ per kg per hour) of each fish, in a respirometer.
Dai et al. (2020) examined the relationships between above ground (AGB) and below ground (BGB) plant biomass from 80 sites across four types of grassland (temperate grassland, desert grassland, alpine meadow, meadow steppe) in a region of China.
One of the consequences of inbreeding in animal populations is that it is thought to increase the susceptibility of individuals to disease. To assess this Townsend et al. (2018) did genetic analysis of 178 crows found across California, and assessed their level of homozygosity (homozygosity by locus - HL), a measure of how inbred they were (higher levels of HL = more inbred). They also took blood samples from the same crows to check for the presence of avian malaria (Plasmodium), a common disease.
Senadheera et al. (2012) tested whether vitamin B6 affects fatty acid metabolism in cultured Rainbow trout, as part of a research program optimising the feeding of these fish. Fish were fed one of four experimental diets and the diets only differed in the amount of B6. Treatments were applied to tanks containing 20 small fish, with three tanks per treatment. For each tank, they determined mean fatty acid metabolism, adjusted for fish biomass, as nmol g-1 d-1.
Note: not open source, and need to get data if any further exploration is used
Quolls are carnivorous marsupials of Australia. In southeastern Australia they live in dense forests and are endangered. A recent environmental concern has been raised about the risks from PFAS (Per- and Polyfluoroalkyl Substances). PFAS is a group of compounds widely used in firefighting, and they can be present around rural airports, firefighting training facilities, etc, which may be near quoll habitat. We wish to understand the risk posed by PFAS and we will visit sites with a wide range of PFAS concentrations. It’s been suggested that PFAS affects reproductive performance, so we will sample quolls during their reproductive season. Our target species, spot-tailed quolls, have litters of up to 6, carried in a simple pouch. Data collection involves collecting individual female quolls, counting their young, and taking a soil sample to estimate PFAS levels.