Discussion Points – Dec. 2nd Huffaker (1958) & Ong et al (2018)
· Overall thoughts on each paper – what people liked, disliked, didn’t understand
· Contrasting the classic paper & the modern
o similarities and differences
o how Ong built on & expanded Huffaker’s work
· Connection between these experiments and previous mathematical/theoretical studies (e.g. Lotka-Volterra) regarding cyclic predator-prey dynamics in nature
o Conclusions & applying concepts to management decisions, the impact of monoculture, etc.
o Comparison between Huffaker’s conclusions vs. Gause’s experiments which demonstrated predator-prey species eventually reaching extinction
· Thoughts on Ong et al’s distinction between stable & effective biological controls
· Thoughts on Huffaker’s methods of introducing aids in dispersal and barriers/impediments to dispersal
· Differences in how Huffaker & Ong et al created spatial heterogeneity in their experimental set-up
· Ong et al’s conclusions regarding two biological control agents (ladybird beetles & an entomopathogenic fungus) compared to Huffaker’s experiment using only one predator species
· At the time of Huffaker’s publication, it was a “much debated question” as to whether the “predator-prey relation is inherently self-annihilative.”
o Is this still a debated question in ecology?
o Are there examples of the “self-annihilative” predator-prey dynamics in modern natural systems?
· Why is the lynx-hare example is more used commonly than Huffaker’s data (specifically Figure 18) as the “textbook example” for predator-prey oscillations?
I wasn't sure how many of these questions to address in my post, so I just discussed the ones that I was thinking about most intently as I read the articles - hope that's okay!
ReplyDeleteOverall Thoughts (pros and cons of both papers):
The meticulousness of the Huffaker mite paper was impressive, and I really appreciated his candidness in discussing how certain techniques that were employed failed – this is rarely discussed in papers today! I did wonder how he accounted for population reductions of both predators and prey that occurred when oranges were removed from the study. He mentioned that efforts were made to not remove oranges that had a substantial number of mites, but what if those that were removed had the most fecund females, or a higher proportion of females, so as to skew the population growth within a given “universe” thereafter? I also wish Huffaker would have discussed the life history of the predator and prey mites in much more detail (especially before the conclusion!), as these would have had a major effect on population growth. I really enjoyed Ong et al.’s introduction to the theoretical frameworks that have been proposed to describe predator-prey dynamics over the last several decades. I felt like I would have benefitted from the authors including a simple diagram of their experimental design, as well as a more useful description of why they chose to use lattice models as opposed to other time-stepping modeling approaches. I appreciated the data they showed to explain their results in Figures 1 and 2, but they were both very busy and not well-labeled (they needed a legend!). The conceptual model was useful and provided a nice takeaway, but again not very aesthetically pleasing.
Ong et al’s distinction between stable & effective biological controls:
I had never heard the term “autonomous biological control” to describe stability in populations of natural enemies, and it was interesting to hear their take on what stability means in this context. I thought their distinction between two types of biological control was fairly intuitive, the main takeaway being that the presence of natural enemies will stabilize pest populations around an equilibrium lower than what is expected in the absence of predators (thus sustaining predator populations and avoiding “annihilation”.
Ong et al’s conclusions regarding two biological control agents (ladybird beetles & an entomopathogenic fungus) compared to Huffaker’s experiment using only one predator species:
I thought Ong et al’s inclusion of an additional biological control was a useful extension on Huffaker’s single-predator experiments, and mimicked situations that often occur both in agricultural and forested systems. It was really neat to see replicates of the two-agent experiment carried out in a controlled environment to test the interaction of the two biological controls, which can be very hard to attribute when there are numerous other confounding factors present in a more complex environment.
I am not sure if we are supposed to leave comments or not, but I will leave one passing thought I had: with both papers, migration was the key to escape the pressures of heavy predation. What can be said, then, about a limited ability to migrate? I am thinking most specifically about island communities. If there is no place to go, does that mean extinction?
ReplyDeleteI enjoyed these two papers, especially the older one. Although a bit long, it was nice to see the author think critically about the extent to which the laboratory results could be extended to the field, and how to design the experiment so that results could apply in other contexts. The new paper was a nice follow-up: it summarized the Huffaker paper and the context in which it was written and described interesting new results.
ReplyDeleteI like the Huffaker’s paper, especially the detailed experimental design, including the trials and errors in the method part. Before reading this paper, I cannot imagine setting a microcosm using an orange.
ReplyDeleteMy main questions are about the companion paper. The effective biological controls make sense to me. But what’s the difference between stable non-effective biological control and leaving the pest alone? Overall, I like the way they use corridors of different sizes to simulate different dispersal capacity. I don’t like the way the authors explain the theories and the findings. To me, they tend to bring out some terms without defining them. For example, what is “nonlinear trait-mediated effect”? Some other questions&concerns: 1. I do not work on pest control and I guess I was lost in the introduction where the authors explained how the 2 alternative mechanisms worked when more than 2 natural enemies encountered (page 3). What is the difference between spatial heterogeneity and spatial clustering? How could there be more refuges due to more enemies? Why less refuges means more outbreaks (does this mean localized outbreaks)? 2. Pathogenic fungi as a natural enemy and “compete” with the animal predator. Fungi work in a completely different way than animal predators. At least, since fungi spread by spores and hyphae (plus infectants), I don’t think those “spatial refugee” would efficiently work on fungi. 3. Figure 1 and 2 should have a legend for those different colors.
Is it still debated if “predator-prey relation is inherently self-annihilative.”?
ReplyDeleteI don’t think this is a debated question in ecology anymore. As Huffaker pointed out, the answer to this question is scale dependent and spatial heterogeneity can reduce predator or prey extirpation. Some examples of predators driving prey extinct would be introduction of novel predators (rats, cats, snakes) on islands.
I really the liked Ong et al. paper’s combination of microcosm and modeling. I think their finding that high-connectivity can facilitate “complementarity” (spatial/temporal niche partitioning) among control agents was cool. However, I do have some reservations about the findings. Their model doesn’t include beetle or fungal abundances so their projections about the aphids don’t really account for the dynamics of the beetle or fungal pathogen which may be important. They just summarize the effects of the beetle or fungus as their effect on aphid growth rates and dispersal. This simplification makes sense, especially for estimating parameters, but I think the changes in aphid traits would depend on the density/prevalence of the enemies. Yuguo’s point about fungal transmission made me wonder how important their infection method (spraying all aphids with infected solution) was to their results, since it is unclear to me aphids would be exposed like this is real settings.
- David
I really liked the older paper. I found the experimental design inspired and resourceful. I also really liked how they mentioned the different things they tried to get it to work. One thing I have discovered is that a lot of science is troubleshooting. Including the trials and errors not only humanizes the experiment, but helps those who may attempt to replicate and improve upon it.
ReplyDeleteI think the lynx and hare graph is used more because it does show repeated cycles, unlike many of Huffaker's, but it is also a natural experiment, done on an island. Some people (obvoisly not myself) question the validity of findings done in a microcosm.
-Miranda
My thoughts:
ReplyDeleteThe older paper had extensively outlined methods and an amazing experimental design. The lengths they went to in order to imitate habitat heterogeneity were admirable.
Ong et al. was a cool follow-up to Huffaker, adding an extra competitive element into the mix. I wished that Ong et al. had used more intuitive figures like Huffaker.
In response to why this is not used compared to the lynx-hare system: in addition to Miranda's point, I think mites are much less charismatic than mammals. This paper also focused heavily on the effects of habitat heterogeneity on dispersal, which I think makes this a less straight-forward example of predator-prey oscillation.