For today, our fine teams presented their proposal drafts to the class and received feedback. As Louie pointed out, it can be somewhat unnerving to have our work so heavily scrutinized. In the end, however, it is in the best interest of improving our research. So naturally, the class was quick to objectively (and constructively) tear each of the proposals to pieces in hopes that they could be re-forged into truly bad-ass project proposals.
… FOR SCIENCE!!!
Following are copies of the proposal drafts (In italics) and subsequent feedback notes:
1) Substrate-borne Vibrational Disturbance of Arthropod Communities
Many insects are sensitive to substrate-borne vibrations. As many insects cannot “hear”, many will often use vibrations from the substrate to detect prey or predators. If such cues were to be disrupted, it could result in significant costs to a given insect. This raises the question: how do insect communities respond to vibrational disturbances? One might expect that more sensitive arthropods would vacate in search of less disturbed habitat, which could lead to a significantly changed community structure in areas near the disturbance source. Both vibrational disturbances from human sources such as passing cars near roadways, construction sites, and power generators, and those from other sources such as vertebrate burrowing, would all be applicable to our experiment. If these effects are profound enough they could have significant implications on food webs and other community level ecological functions.
How does persistent disturbance from substrate borne vibrations affect community composition (abundance and diversity) of arthropods in leaf litter systems?
We suspect that the diversity and abundance of arthropod communities increases when they are farther away from a disturbance source.
Recording: First we would sample vibrational sounds from commonly occurring disturbance sources (Highways, Generators, Vertebrate Burrowing Behavior (Whichever we decide)). We could accomplish this using Piezo Electric Disks and a recording device.
Set-Up: We would set up circular sampling rings (with a radius of 4 meters). The disturbance source (subwoofer or Cement vibrator rod in the soil) will be placed dead center. The perimeter of the ring will be lined with chicken wire and the area will be covered with a net that is permeable to arthropods but will prevent leaf litter from being blown away. The rings will be planted with equal amounts of a homogenous mixture of leaf litter (from live leaves (e.g. from Coast Live Oak) that are frozen for sterilization). Rings will be spaced far from one another with sound/vibration dampening barriers in between them.
Treatments: After a Colonization period, the 3 Treatments will be implemented (High Magnitude, Low Magnitude, and Control) with at least five replicates per treatment (15 rings total at minimum)
Sampling: leaf litter sampling will be conducted at key points during the implementation period (e.g. after 1 day, 5 days, and 10 days). Samples of 1ft^2 Quadrats will be collected along a 4m transect that reaches from the vibrational source to the edge of the ring. These samples will be taken at 1 meter, 2 meters, and 3 meters away from the vibrational source. Arthropods will be extracted from the samples in lab using a Berlesse Funnel (or Winkler Bags).
We would expect biodiversity and abundance to be lower in samples that are close to the disturbance source and progressively increase with distance away from the disturbance.
- It could be important to look into mechanisms at the individual level that might ultimately result in a shift in community structure.
- An 8m diameter ring is quite a huge area for a single replicate to cover. It may be best to condense the size of each replicate.
- How will we know if recordings we take are reliable?
- How will we analyze the data? More specifically what kind of figures will we use?
- How expensive is the equipment we would need? Or how might we go about acquiring it?
2) Spiders and Light Pollution
Introduction Larger Implications:
Effects of urban light pollution on predator-prey interactions could lead to trophic cascades and destabilization.
Questions & Hypothesis
Hypothesis: Urban lighting effects predator-prey interactions & densities among P. Princeps & C. Carnea.
1. Feeding Pilot Experiment: (In a lab setting) One spider caged and given a fixed surplus of Green Lacewing. After one week, we will record how many Lacewing the spider ate and use that number to establish a rough “maximum” feeding rate. We will base future prey starting allotments based on this number.
2. Enclosure design: We plan for our enclosures to be made of aluminum flashing, circular, and two feet in diameter. Our flashing will be 16 inches tall, with the bottom 4″ buried to ensure a degree of exclusion. The remaining flashing will rise 12″ above the ground, and will be drummed with fine mesh across the top to ensure lacewings cannot escape. Each enclosure will be capped with a semi-transparent, perforated cone. This cone will allow transmission of daylight into the enclosure, but will act to exclude other night-time light sources. The cone will be removed during day-time sampling. We will have a total of 45 replicate enclosures. 15 LED-lit enclosures, 15 sodium lit, and 15 day-light (control). These will be arranged in a grid pattern, 3×15, with barriers between each of the three rows to prevent light inter-pollution.
It will appear something light this:
LED LED LED LED LED LED LED LED LED LED LED LED LED LED LED
So. So. So. So. So. So. So. So. So. So. So. So. So. So. So.
DL. DL. DL. DL. DL. DL. DL. DL. DL. DL. DL. DL. DL. DL. DL.
Where LED implies LED lighting, So. implies Sodium lighting, and DL. implies daylight only.
3. Besides having a number of enclosures, we will also be repeating the entire experiment (recycling all 45 enclosures) after all lacewings have expired (either by predation, or by lifespan). This way we can collect many replicate data sets across a variety of seasonal changes.
Our sampling will involve two methods. First, starting and ending counts will be taken on both predator and prey densities at the beginning and end of each experiment’s period respectively. Second, twice-weekly visual sampling will take place on each enclosure. During visual sampling, the cone will be removed, and researchers will visually count how many spiders they see, and how many Lacewings. Final counts will be attained by “BugVac-ing” each enclosure.
Expected Results & Outcomes
We expect to see a correlation in our data between LED lighting and the effects of P. Princeps on C. Carnea. Specifically, we expect that LED lighting will exhibit more of an effect than Sodium lighting, and that both will effect predator prey interactions more than the control.
- There was concern over the accuracy and reliability of data taken via visual sampling.
- It could be problematic to set all the treatment types in a row. Instead it would be best to intersperse each treatment across a field site. However, this would also entail installing more light barriers.
- How will we account for the fact that lacewings are attracted to lights and will likely be flying around at the top of the enclosure at night.
3) Galls and Ecosystem Engineers
Physical ecosystem engineers physically alter biotic or abiotic material, often by creating or modifying habitat. This can then directly or indirectly affect the availability of resources to other organisms in the community. Physical engineering has both negative and positive effects on species richness and abundances and the scale of these effects vary greatly depending on the system and the engineer (Jones et al. 1997). One study has shown that goldenrod bunch gall midges are ecosystem engineers (Crawford et al. 2007), though none have looked at oak galls created by cynipid wasps. We want to see if cynipid wasps function as ecosystem engineers and what affect oak galls have on the rest of the insect community.
How do oak galls (as novel shelters) affect insect community structure on oaks?
Insect communities on oaks with galls will have higher species richness than those without galls.
First we would examine the local insect community composition of each sites before starting the experiment. Varies of methods will be used depending on the situation.
Active collecting: portable suction devices, pooter, sweepnet, visual observation. Passive collecting: colored pan traps, light traps, Malaise traps, pitfall traps, emergence traps, sticky traps, or suction traps.
Then we would divide the site into 5 treatments, and remove pre-existing insect galls completely in 4 treatments. For the 4 treatments where galls were removed we would attach prepared sterilized galls to branches at different heights. Each gall will be recorded by its size and position (Diameter, height of branch, tree number). And each of these 4 treatments will have a different density of galls attached. Also galls will be laid on ground under each tree to mimic old galls that fell off of branches.
Each week insect behavior will be observed visually until community composition seems stable. Then another complete examination of community structure will be conducted with similar ways at the beginning of the experiment except all galls will be recollected and checked for changes. Result will be based on comparison with the controlled treatment with no disturbance.
Expected results and outcomes:
We believe that the presence of galls will increase species richness withing the insect communities on oak trees.
Spiders are sometimes secondary users of oak galls (Wheeler and Longino 1988). If predatory spiders become secondary users in this study, we would expect to see a negative effect on the most abundant herbivore (prey) species in the community and an increase in species diversity.
- It was suggested that each treatment be blocked within single trees. This way we can avoid dealing with differential health/traits/conditions of trees in the study. This will also simplify the number of trees needed for the experiment. However, there is some concern for how treatments within a tree might interact with one another.
- One Logistical Concern was the amount of tree climbing that would be required to survey for invertebrates (although some among us seemed rather enthusiastic about such endeavors).
- It is unclear just how sampling techniques could be used to take an accurate “snapshot” of each system.
- We might need to add fake galls as a control.
- What would a figure look like for depicting community structure in the different treatments?
4) Aggregative behaviors in Pipevine swallowtails larvae in different density treatment with exposure to predators
Introduction Many studies have been done in order to understand the adaptive strategies of aggregative feeding in pipevine swallowtail, Battus philenor. However, this study will investigate the role of the threat of predation on pipevine swallowtail larvae and its effect on feeding behaviors and plant consumption. We aim to simulate predation risks in order to determine the extent of how predators influence prey behavior.
Question and Hypothesis Do the aggregative feeding behaviors of pipevine swallowtail larvae change in response to the threat of predation?
Hypothesis: At larger densities the risk of predation promotes increased feeding and herbivory.
Methods For this experiment we will set up 66 square plots 0.5 meters by 0.5 meters containing a pipevine plant and a specified number of larvae (1, 5, 10, 15, 20 or 25). Predators will be excluded through the use of screens that cover each plot and the organisms in them. For each density of larvae there will be 10 replicates as well as a one control where predation is not mimicked.
Pipevine swallowtail larvae will be collected from the UC Davis Arboretum or Stebbins Cold Canyon. Approximately 836 individual pipevine swallowtail eggs will need to be collected. Once collected the clutches will be placed in plastic containers and labeled. All eggs that comprise one clutch will be kept in one container together. Clutches will be kept in incubators where the temperature can be controlled to synchronize hatching. The 66 pipevine plants needed will be purchased (or hopefully donated) by the UC Davis Arboretum.
Once eggs have hatched, the plots will be set up. Larvae will be selected for each plot by a random number generator. Individuals from same clutch will not be placed in the same plot together to control for the possible effects of genetic relatedness. After being placed in the plot, the larvae will be given a day to acclimate.
Predation will be mimicked using forceps to agitate the caterpillars. Each of the caterpillars will be pinched for 15 second intervals twice a day, once in the morning and once in the afternoon. All individuals in each plot will be subjected to mimicked predation. The effects of simulated predation will be monitored by recording the consumption rates of each plant by counting the number of leaves left after each feeding session.
Alternative Methods We can also expose each density of pipevine swallowtail larvae with a parasitic ichneumon wasp in order to simulate predation. This will require capturing many ichneumon wasps and keeping them alive for the duration of the experiment. We would also tailor each cage cover to have a wasp holder in order for the wasp to release its pheromones yet not be able to parasitize the larvae.
Things Left to Address What happens when the larvae eat the entire plant? How long will it take for them to eat an entire plant?
Expected Results and Outcomes We expect that caterpillar at higher densities with constant predation will consume more plant material in a shorter amount of time than caterpillars at low densities.
- As mentioned in the proposal, what would occur if caterpillars consumed the entire plant?
- Louie suggested the possibility of introducing predators with snipped ovipositors
- In order to distinguish the effects of density on herbivory and the effects of predator simulations, it was suggested that the project be run as a 2 factor experiment (Density X Predation)
- Would we be able to collect enough Pipevine Swallowtails for this experiment?
5) Mites and Metapopulations
Introduction: Many studies have been done with metapopulation and mites with predator-prey interactions; however, not many studies have studied the effects the phytophagous mites in the absence of the predaceous mites and have determined the ideal ratio of mites in a system for an optimal predator-prey cycle.
Question: What is the optimal ratio at which predaceous and phytophagous mites co-exist, and what effect does the absence of predaceous mites have on the phytophagous mites?
Hypothesis: The optimal ratio at which predaceous and phytophagous mites co-exist is around 100 phytophagous mites to 20 predaceous mites. In addition, the absence of predaceous mites will have a positive effect on the phytophagous mites.
Methods: First, we will grow 33 Lima Bean Plants in our Lab to ensure that no other organisms will be on the plants.
While the plants are growing in our lab, we will find and capture 3300 phytophagous mites and 1650 predaceous mites with aspirators.
When the Lima Beans have matured, we will transfer them to the student farm field with a proper netting around each plot.
Finally, we will put the mites into each plot. We will have 11 different treatments with 3 replicates each.
- 100 phyto mites – 0 pred mite
- 100 phyto mites – 10 pred mites
- 100 phyto mites – 20 pred mites
- 100 phyto mites – 30 pred mites
- 100 phyto mites – 40 pred mites
- 100 phyto mites – 50 pred mites
- 100 phyto mites – 60 pred mites
- 100 phyto mites – 70 pred mites
- 100 phyto mites – 80 pred mites
- 100 phyto mites – 90 pred mites
- 100 phyto mites – 100 pred mites
1100 mites phyto mites x 3 = 3300 phyto mites
550 mites pred x 3 = 1650 predaceous mites
We will observe each community using portable microscopes in combination with magnifying glasses brought to the field. We will use tally counters in order to keep track of the number of each species still visible in the plot. For the first two weeks, we should check the plots every day since the greatest amount of change should take place. Then, as the populations level out, we can check every other day or twice a week.
Things Left to Address: How to efficiently count mites? A better way to efficiently collect mites? Time sensitive observations (can all be eaten in one night before we can even look at them)? Still have the issue of proper netting (thinking tights stretched over pvc pipes shaped into a cube)?
Expected Results: The optimal ratio should be around 100 phytophagous to 10 or 20 predaceous mites. Having more than 30 predaceous mites would allow them to eat all the phytophagous mites, which would drive both species to extinction since the predaceous mites will have nothing else to feed on. That is the point at which you could use the predatory mites as pesticides. Under 30 pred mites, the predaceous will eat the phytophagous mites but there will be less competition between the predaceous mites and less predation on the phytophagous mites; therefore, the phytophagous mites will have enough time to respond. A predator-prey cycle will begin and the prey population begins to increase while the predator population is still decreasing and the prey population decreases while the predator population is still increasing.
- How will we observe and process thousands of mites (As mentioned in the proposal)?
- The figures produced would essentially model predator-prey population cycles. The concern is whether this information would be novel. This proposal could benefit from taking on a new direction or adding some other element into the question (e.g. to see how predator-prey cycles might be affected by other factors?).
So there we have it folks! After an intensive mauling of proposals, it is time for the teams to regroup and rebuild! Its gonna be okay.
Before breaking off, we discussed plans for next class period… On Tuesday we will be driving to visit some field sites. Namely, we would like to visit the oak grove sites, areas along putah creek, and possibly revisit the student farms. This day will serve as a reality check. We will go to these sites to try to envision our projects taking place.
In the interest of keeping our budget healthy, we’ve decided to carpool rather than rent university vans. Wenbo, Nuray, and Robyn have volunteered to drive! They will park at the loading doc (There is 30 minute parking at the loading doc). We will meet and quickly de-brief in the lab and then be on our merry way.
ASSIGNMENTS FOR TUESDAY!
We will revamp our proposals. This time we have a rather generous 1200 word limit. Lots of detail is encouraged. It would also be beneficial to include diagrams of the experimental design and include example figures for data in the expected results section. To gain a sense a feasibility, we should also include a budget to account for the costs of all the equipment we would need to buy. HAVE AT IT!
Sign up for it here. This will allow us to park on campus for occasions when we need to get out to the field. We’ll need to pick up passes at TAPS.