Parks 1948 & White et al. 2019

Use this to make comments on the reading for Monday November 25, 2019.

Kettlewell, 1955; Nosil et al., 2018

Papers: 

Kettlewell HBD. 1955. Selection experiments on industrial melanism in the Lepidoptera. Heredity 9: 323–342.

Nosil P, Villoutreix R, de Carvalho CF, Farkas TE, Soria-Carrasco V, Feder JL, Crespi BJ, Gompert Z. 2018. Natural selection and the predictability of evolution in Timemastick insects. Science 359: 765–770.

Blogpost: Yuguo Yang

Author background:

Henry Bernard Davis Kettlewell was a British geneticist who worked on Lepidoptera (moth and butterfly). He was a researcher in Department of Zoology in Oxford University who conducted the classic study about natural selection – the influence of industrial melanism on peppered moth coloration.

Patrik Nosil is a independent research fellow in University of Sheffield, UK. His research is mainly about evolutionary processes that drives speciation. 

Kettlewell 1955

The peppered moth (Biston betularia) has 3 phenotypes: 1.typical, which is white color with black dots. 2.carbonaria, which is a melanistic type with completely black color. 3. insularia, which is a less complete melanism – dark color with white scales. The purpose of this study was to figure out whether the different colored moths can take advantages (i.e. “cryptic”) from the background color and whether these moths were eaten by the predators selectively due to their visibility. 

To study the conspicuousness of moth on there background, different moths were judged by walking away from them until the moths became invisible. The results showed that the crypsis of moths from human eyes were highly dependent on whether the moths’ color matched the background. To test whether the moths were taken by predators differently due to the camouflage, an aviary experiment was conducted using 2 great tits (Parus major) in a cage. As a result, moths on incorrect background had higher chance to be eaten.

Then the author conducted a release-recapture study in an industrially smoked area where the proportion of birch (all moths protected) to oak (dark moths protected) was less than 1:10. 27.5% carbonaria, 13% typical, and 17.4% insularia males were recaptured after releasing. In addition, local population had 85.03% carbonaria, 10.14% typical, and 4.83 insularia. From the author’s observation, although the detection of conspicuous moth would make other moths nearby at a disadvantage due to the active searching of predators, there still were a evidence that predators had biased predation due to crypsis. 

Nosil et al. 2018

The aim of this paper was to study the predictability of evolution in walking stick insects (Timema cristinae). T. cristinae has 3 morphs: 1. striped green that is cryptic on the leaves of Adenostoma fasciculatum, 2. unstriped green that is cryptic on the leaves of Ceanothus spinosus, 3. melanistic form that is cryptic on the stems of both plants above. The morphs are controlled by 3 alleles where green is dominant to melanistic, and unstriped is dominant to striped. 

The authors used sequences from 3 datasets to quantify the changes in allele frequency overtime. The result showed that Mel-stripe (the loci controlling body color and strip) had the highest temporal allele frequency change in all the datasets, which was far beyond what can be explained by dispersal. The authors thus attributed this change to selection.

Predictability of evolution was quantified using autoregressive moving average models (ARMA). The model analysis indicated that the temporal change in color-morph frequency (green vs. melanistic) can be only moderately predicted because complex and contradictory factors were driving it, whereas the temporal change in pattern-morph frequency were highly predictable possibly due to negative frequency-dependent selection (NFDS). Then the authors conducted a transplant experiment to verify the NFDS. 1000 insects (green striped and green unstriped) were transplanted into 20 A. fasciculatumwith either 4:1 or 1:4 ratio. Partly congruent with the hypothesis, the striped morph had strong selection preference when the initial proportion was low. 

My thoughts

The kettlewell’s moth paper is one of the most famous study in intro-biology textbook. I like the flow of the paper as well as the step-by-step experimental design. The aviary experiment after human visual experiment is reasonable but the sample size was small, and I think it would be better if more than one bird species are tested. Overall, this paper provided solid results of evolution driven by selection. I especially like how the author justified the conclusion by refuting the potential alternative explanations such as biased recapture, different lifespan, migration, etc. The companion paper studied another insect species that had similar types of morph as peppered moth. This paper is highly compacted and I am not familiar with the model in the paper, but I find it interesting that temporal change of color morph is driven by counteracting sources. It will be great if a field study can be conducted to address the relative effect of those selection sources.

  

Brooks and Dodson 1965, Barneche et al. 2018, & Andersen et al. 2019

Papers:

Brooks, J. L. and S.I. Dodson. 1965. Body Size, and Composition of Plankton. Science, New       Series, 150(3692): 28-35.

Barneche, D.R., D. R. Robertson, C.R. White, and D.J. Marshall. 2018. Fish reproductive-energy            output increases disproportionately with body size. Science 360, 642–645. 

Andersen, K.H., N.S. Jacobsen, and D. van Denderen. 2019. Limited impact of big fish mothers for population replenishment. Canadian Journal of Fisheries and Aquatic Science 76:347–349. 

Blog Author: Lyndsie Wszola

John Langdon Brooks

Brooks was an evolutionary ecologist who primarily focused on freshwater systems. Throughout his research career, which included undergraduate and graduate education at Yale with G.E. Hutchinson, he focused on ecological and evolutionary interactions between freshwater fauna including fish and plankton. Later in his career, he became a program officer and later director of the division of environmental biology at NSF. 

Diego Barneche

Barneche is an independent research fellow and lecturer at the Unviersity of Exeter who focuses mainly on marine systems. He is a quantitative ecologist who seeks to use mathematical, statistical, and theoretical models to answer basic science questions and inform management. 

Ken H. Andersen

Anderson is a professor of theoretical marine ecology at the Technical University of Denmark. His work focuses on theoretical and applied models of fish evolution, ecology, behavior, and exploitation. The unifying factor in his work is a focus on size and trait-based modeling. 

Brooks and Dodson:

The Brooks and Dodson paper asks what effect the addition of a planktivorous fish, the alewife, has on the community composition and size distribution of the zooplankton in a freshwater lake in Connecticut. They begin with the observation that lakes with naturally populations of the extremely invasive alewife lacked large species of zooplankton. They then establish a natural experiment in which they compared plankton size and community composition form Crystal Lake, which naturally lacks alewife, before and after alewife introduction. They found a marked shift in the community composition and size distribution of zooplankton in the lake towards smaller species. They explained this finding by hypothesizing that the alewife, a planktivorous fish, should prefer larger prey because they are more energetically efficient. They then hypothesize that an alewife preference for larger prey should eliminate those large prey from the food web, releasing competition for smaller zooplankton and causing the observed shift in community composition and size distribution. Essentially, though they don’t use these words, they are claiming to observe a trophic cascade via competition, something which is widespread and powerful in aquatic systems. 

Barneche et al.

Barneche et al. begin by identifying the classically held assumption that fish reproductive output scales linearly with body size. This assumption informs many stock and harvest models that are used for both basic science and management. Barneche at al. propose that this assumption is fundamentally incorrect and can lead to harmful mismanagement. Using a large meta-analysis, they demonstrate that fish reproductive output actually increases hyper-geometrically with fish body size.  This means, in essence, that one very large fish should have a much higher reproductive output than two smaller fish whose body mass adds up to the same size. Barneche et al. extrapolate this finding to suggest that typical harvest models are vastly underestimating the contribution of large females to fish stocks. They further more suggest, somewhat dramatically, that forces such as warming and over-exploitation, which are driving down fish body size, will have a powerful negative effect on the ability of fish populations to sustain themselves. 

Andersen et al.

Andersen at al. wrote their short communication in response to the Barneche et al. article. They counter the claims in the Barneche piece by making two arguments: 

1.    Barneche et al. over-estimated the relationship between body size and reproductive output.

2.    Stock replenishment  does not depend solely on reproductive output.

Andersen et al. pursue the first argument by adding some realism to the Barneche model. They make the point that most small individuals are not reproducing, and that including them in models is therefore disingenuous (that is actually debatable). They continue by saying that very large individuals are also very rare, and that they cannot therefore be extremely important to populations (again, there is very good evidence that this was not always true). Andersen et al then replot the dramatic figure from the Barneche et al. paper with what they propose is a more reasonable fit and show that there is a much less significant difference between linear and hyper-geometric assumptions when replotted. Finally, they add more realism to the discussion by saying that reproductive output is not the sole determinant of stock dynamics. Young fish experience density-dependent mortality and few eggs survive to adulthood, so there is often a tenuous relationship between total egg production and recruitment. They conclude by emphasizing that the Barneche et al. paper is responding to an urgent need, but that adding biological realism raises questions between the theoretical work and application.

My thoughts

The Brooks and Dodson paper is an interesting early work on trophic cascades, even though they don’t use those words to describe the dynamics. It is an elegant natural experiment, but I thought they made some very significant assumptions, especially that alewife were actively visually searching for their prey, and that the decline of large zooplankton led directly to a boom in small zooplankton. In a modern context, I would want much clearer mechanistic links between each step in their reasoning process. 

I really enjoyed the Barneche paper and the Andersen response. Barneche et al. make impressive strides from theoretical work to data mining to management implications. However, I agree with Andersen et al. that the Barneche paper overstates some of its findings and doesn’t adequately address the complexity of aquatic ecosystems. I found the point about density dependence particularly compelling. As someone who seeks to do this kind of work, the discussion between these two authors emphasizes the perils of trying to build workflows that go from theory to data to practice. It’s incredibly difficult to build models that are scientifically interesting, ecologically sound, and practically implementable. In my experience, the only way to actually do this is to have a diverse author team that includes mathematical modeling experts, theoreticians, field biologists and managers. In other words, I would be very interested to read a paper written by both sets of authors together. I’m very curious what others think about these two papers and whether you are more swayed by one argument or the other.

MacArthur 1958 & Remold et al. 2011

MacArthur, R.H., “Population Ecology of Some Warblers of Northeastern Coniferous Forests.” Ecology, Vol. 39 No. 4 (Oct 1958), p. 599-618).

Remold, S.K., Brown, C.K., Farris, J.E., Hundley, T.C., Perpich, J.A., Purdy, M.E., “Differential Habitat Use and Niche Partitioning byPseudomonas Species in Human Homes.” Microbial Ecology, Vol 62 (2011), p. 505-517. 

 Blog Author: Crystal Uminski

Robert H. MacArthur (1930-1972)was an American ecologist. In this course, we previously read MacArthur’s work “On optimal use of a patchy environment” (1966). MacArthur completed the work for the warbler paper for his Ph.D. thesis. Upon the time of the paper’s publication in 1958, MacArthur had just started as a professor at the University of Pennsylvania. MacArthur was later a professor at Princeton University.

Susanna Remold is an associate professor in the biology department at the University of Louisville. Her research focus is on the distribution and phenotypic variability of the Pseudomonasbacteria found in human homes. 

MacArthur (1958)

MacArthur observed that there were five species of warblers with similar food sources (insects) living in the same habitat (mature boreal forests). The focus of MacArthur’s paper was to determine how these five species with seemingly overlapping niches were able to coexist. MacArthur also aimed to figure out the limiting factors on the five warbler populations. 

MacArthur’s study was divided into four parts:

Part 1) Density dependent events that regulate warbler populations
Part 2) General ecology of warblers (feeding behaviors, nest positions, territoriality, clutch sizes)
Part 3) Seasonal ecology of warblers (habitat, feeding behaviors)
Part 4) Warbler abundance 

MacArthur conducted his observations of the warbler species between 1956 and 1957. His methods were sometimes a bit questionable. The data about feeding zones was determined by counting seconds manually (“thousand and one, thousand and two,…”) or with a seemingly faulty stopwatch. He also relied heavily upon museum specimens for data about clutch sizes and provided a rationalization about how the “prized” warbler nests “do not reflect any bias,” which is claim that seems a bit dubious. 

His observations and data collection led to the following conclusions for each of the four parts of his study: 

Part 1) MacArthur determined that the warbler populations were primarily regulated by density dependent events. He drew this conclusion by examining data about changes in warbler populations. Each species tended to decrease following an increase and to increase following a decrease. This non-random pattern cannot be attributed to density-independent population regulation, so there must be density dependent factors regulating the warbler populations. 

Part 2) MacArthur divided the arboreal warbler habitat into regions defined by the height and area of the branch and observed how many seconds warblers tended to spend in each region during feeding. Figures 2 – 6 show the feeding positions of the different warbler species. While there was some overlap in the feeding regions between species, each species tended to have distinct preferred feeding regions. MacArthur also observed the feeding behavior of the warblers and noted differences in the species behaviors. He also noted that the nest positions of the warbler species tended to reflect their preferred feeding zones. MacArthur observed territoriality in the warblers and determined that there was greater intraspecific territoriality within a species than interspecific territoriality between species. An examination of clutch sizes and data about the occurrence of budworm outbreaks led MacArthur to conclude that the bay breasted warbler had greater clutch sizes during the years with outbreaks. 

Part 3) The distribution of warblers in winter was generally inconclusive. The five species show the amount of overlapping of winter range that would be expected on a random basis. The general aspects of observed warbler behavior are nearly the same in the summer and winter. 

Part 4) The composition of the warbler populations in different plots is summarized in Figure 10. The Cape May warbler population is mostly dependent on volume of food, but the other species of warblers have populations that are relatively proportional to the volume of foliage in their feeding zones. 

Remold (2011)

The Remold study was conducted to determine if the actual habitat use by Pseudomonas species was as broad as the fundamental niche. The habitat examined in the study was surfaces and structures in human homes. The paper also addressed the degree to which the realized niches of Pseudomonas species overlapped. 

Twenty households were sampled in the study, and within each household, between 25 and 96 samples were collected. Sampled surfaces and structures included human skin, animal foot pads, garbage bins, shower drains, and the soil of houseplants (a more complete list in Table 1). The samples were plated on Pseudomonas-isolating agar and incubated. The species of Pseudomonas in each viable sample was recorded. 

Pseudomonas species were recovered from and were categorized as being from a vertebrate (internal), vertebrate (skin), surfaces, water, drain, soil, or garbage. Some of the Pseudomonas species displayed specificity to certain environments. P. delhiensis showed specificity to the soil of house plants, while P. oryzihabitans was unique to outdoor soil. P. aeruginosa was most commonly in the drains in bathroom sinks, while P. plecoglossicida was more frequently isolated from the drains in tubs and showers. The different Pseudomonas species differed in their distribution among sites, which provides evidence that the realized niches of Pseudomonas are narrower than their fundamental niches.

Thoughts

The MacArthur study is the textbook example of niche partitioning, so it is fascinating to go back and see the original document. It is also a bit horrifying to think about how poorly this paper is interpreted in introductory biology classes. I remember seeing one iteration of the warbler diagram in which all five species of warbler were represented on one tree where each species had a very definitive feeding zone that excluded all the other birds. After seeing MacArthur’s original figures, the actual “partitioning” of the tree spaces is much less clear cut. For example, four of the five species use the T2 zone and three of the five use the M3 zone. I also thought that some of MacArthur’s methods were a bit fuzzy, but I do have to consider the technological limitations of the 1950s. It is also a bit amusing to consider that the main conclusions about the warbler feeding zones were based on just over 4 hours of recorded observation (though MacArthur did acknowledge that the warblers were often difficult to see in the densest areas of foliage). I liked the Remold paper because it covered the ecology of bacteria (which is something that we have not spent all too much time discussing in class yet). The paper was from 2011, so in the time since the original publication, given the fast rate at bacterial reproduction (and consequently evolution), I am curious to know if the houses in the study were re-sampled, would the same species be present in the same distributions and abundances? 

Davis 1969 & Calder and Shuman 2019

Author

Stella Uiterwaal

Citations

Calder, W.J., Shuman, B., 2019. Detecting past changes in vegetation resilience in the context of a changing climate. Biology Letters 15, 20180768. https://doi.org/10.1098/rsbl.2018.0768

Davis, M.B., 1969. Climatic Changes in Southern Connecticut Recorded by Pollen Deposition at Rogers Lake. Ecology 50, 409–422. https://doi.org/10.2307/1933891

Author Background

Margaret B. Davis – the first (and only) woman in our textbook. She used fossils to study how historic changes in climate influenced communities. She taught at several universities and served as the president of the Ecological Society of America from 1987 to 1988. 

W. John Calder is quantitative paleoecologist who studies links between wildfires, climate, and microbes. He is a postdoc in Alex Buerkle’s lab in Wyoming (the same lab as one of last week’s authors!).

Classic Paper

Fossil pollen in sediment provides a detailed, continuous record of past vegetation. This paper used changes in fossil pollen concentration and deposition rates at Rogers Lake in Connecticut to study vegetation around the lake in the last 14,000 years. To collect pollen, the author and a partner took several cores from which samples were taken for pollen analysis. Ages were determined by radiocarbon dating. Pollen was identified by size and morphology. The author finds evidence for tundra-like vegetation and then a transition to woodlands of various compositions (spruce, oak, fir). She also finds evidence for fir, larch, birch, alder, and pine trees. Around 8,000 years ago, white pine becomes dominant and other plants (like ferns) increase. This is likely due to a shift in climate in the region. After this period, vegetation becomes characteristic of prairie. In the last few centuries, pollen records reflect vegetation changes due to European settlers. The author also describes finding evidence for the introduction of new tree species such as chestnut and hickory in the last few thousand years. She attributes these sudden onsets of new species to migration from glacial refuges. In addition to confirming what other studies have concluded, this paper provides evidence of vegetation transitions that were previously not well understood.

Modern Paper

The authors of this paper studied resilience in palaeoecological records by looking at changes in vegetation in response to wildfires. To do this, they collected pollen and oxygen data from Rogers Lake and Summit Lake, both in the US. They also used previously constructed vegetation and wildfire history information. Wildfire data was obtained by looking for macroscopic charcoal deposits, indicative of high-severity wildifires within 1 to 3 km of a lake. To determine resilience, they used a linear model relating oxygen to conifer pollen percent to generate predicted vegetation values to which they compared observed values. Resistance is then the difference between the predicted value post-disturbance and the actual value. 

Within their period of interest, they found that pollen levels declined and remained low at the Rogers Lake site. About 50% of the variance in pollen levels at this site could be explained by oxygen. At Summit Lake, they also found a decline in pollen over the last 2500 years, also due to oxygen levels. A century of high-frequency wildfires resulted in a noticeable decline in pollen levels, and the conifers never fully recovered from this disturbance. The authors also note that there was a lower response of conifers to climate post-wildfires. The authors conclude that climate was ultimately responsible for the reduction of conifers, but wildfires altered the vegetation-climate equilibrium.

My thoughts

I am impressed and intrigued by the methods used in both papers. I know very little about paleoecology, and it was neat to learn that pollen can be used to reconstruct vegetation composition around lakes. I also like that Rogers Lake was being used for these kinds of studies in the 1960s and is still being used for the same type of research today. A clear limitation of this method is the age of the lake. I wonder if there are older lakes around the world where similar work could be done.

Davidson and Andrewartha 1948 & Harrison et al. 2015

Citations:

Davidson, J., & Andrewartha, H. G. (1948). The influence of rainfall, evaporation and atmospheric temperature on fluctuations in the size of a natural population of Thrips imaginis(Thysanoptera). The Journal of Animal Ecology, 200-222.

Harrison, J. G., Shapiro, A. M., Espeset, A. E., Nice, C. C., Jahner, J. P., & Forister, M. L. (2015). Species with more volatile population dynamics are differentially impacted by weather. Biology letters, 11(2), 20140792.

Blog author: Miranda Salsbery

Author Background:

Prof. J. Davidson was head of the Department of Entomology, Waite Agricultural Research Institute, and a professor of entomology in the University of Adelaide. Dr Davidson actually passed away and this paper was published posthumously. 

 Dr. Josh G. Harrison works on interactions between hosts and symbionts and the ensuing evolutionary consequences for both interactors, focusing in microbial communities and uses lab and field experimentation with large-scale surveys of natural variation using data-intensive methods. He is currently a post-doc in Alex Buerkle's lab at the University of Wyoming. This was his first publication. 

Davidson & Andrewartha (1948)

The main goal of this paper was to investigate density-independent factors that control populations, focusing primarily on how temperature and rainfall correlates with adult thrip population estimates. 

From 1932-1946, adult thrips were counted in 10-20 roses daily (expect for Sundays and holidays) thought the spring and summer in the garden at the Waite Institute in Adelaide, Australia. Weather measurements were taken from a meteorological station close by. The authors performed a series of regressions to determine which weather condition correlated with daily and annual population changes in the thrips. They also tested several dependent variables, including the logarithum of the geometric mean daily counts for 15, 30, and 60 days before maximum daily counts as well as the logarithm of the geometric mean for October and November.  

For changes in population density day to day, maximum temperature was found to the three times as important as rainfall in influencing the number of thrips in the roses. When looking a population year to year, 78% of the variance of the population could be related to environmental factors. The most important of which was the total thermal units (maximum daily temperature minus 48 divided by 2) accumulated between the inferred start date of development for the host plant (the ‘break’ of the season) and August 31^st. Thus, maximum density for the population was largely determined by weather during the proceeding autumn. The author also observed a potential rhythm in the annual maximum density of the population, with a pattern of progressive increase for three to four years followed by a rapid decline for a year, then a progressive increase and so on.  

The real goal of this paper was to show that density-independent factor, like weather, can explain population fluctuations. The author found little evidence to support the idea that competition or other density-dependent factors played a role in determining population density in this system. 

Harrison et al. 2015

Rather than looking at how weather affects a single species, these authors looked to see, and found, that species with high population volatility (population that commonly fluctuate as opposed to remaining stable) are impacted more by certain weather events such as El Nino. They used a large long-term population dynamic dataset of co-occurring butterfly populations and a Bayesian framework. Changes in precipitation had very dissimilar responses between volatile and stable species, most likely by affecting the host plants. Temperature is more complex as it affects more aspect of species ecology such as behavior. This paper is interesting in that it shows species with similar dynamics may respond to climate change similarly.  

My thoughts:

For starters, the thrip paper had way too many tables (23). It also wasn’t written in the most understandable way but more like a stream of consciousness. The variables were confusing.  I do find it very interesting that they look multiple dependent variable as well as independent variable. We don’t do that very often anymore. I also think this paper is really important today as it laid out the initial evidence that the environment can affect populations, which as now grown into a large portion of climate change ecology, which the Harrison paper builds on. I though both papers were a bit short and speculative on ecological explanations for why they saw the patterns they did, especially in the 2015 paper. Even though it was a short a paper, I would have liked to see a more in-depth explanations for their results. 

Porter et al. 1969 & Deutsch et al. 2007

Citations:

Porter, W.P. and Gates, D.M. 1969. Thermodynamic equilibria of animals with environment. Ecological Monographs 39: 227-244.

Deutsch, C.A., et al. 2007. Impacts of climate warming on terrestrial ectotherms across latitude. PNAS 105 (18): 6668-6672.

Blog author: David Nguyen

Author backgrounds:

Porter is currently a professor in the Dept. of Integrative Biology at the University of Wisconsin – Madison where he has continued studying how animal body size and shape influences energetics, behavior, ecology and evolution.

Deutsch is a professor in the School of Oceanography at the University of Washington where he studies the impact of climatic variability on the biodiversity and adaption of terrestrial ectotherms.

Porter and Gates 1969

The premise of Porter and Gates (1969) is that animals must be in energetic equilibrium with their environments to survive. This means that the energy input that an animal receives must equal the amount of energy lost by an animal over a sufficiently long-time scale. If this was assertion was untrue, animals would exhibit trends in cooling or heating over time which has not been observed. Hence, quantifying the set of environmental conditions in which an animal can maintain energetic equilibrium would help us define the fundamental niche of animals.

Porter and Gates (PG) developed mathematical and physical models to quantify how animals gain and lose energy, since modeling is more feasible than attempting to quantify this experimentally over regions in climate space. In their models, PG considered four environmental variables: radiation, air temperature, wind and humidity. Together, these variables constitute the “climate space” animals will experience. The climate space will impact three modeled animal characteristics: body temperature, rate of moisture loss, and metabolic rate. 

The climate space that an animal can survive in can be calculated given information on the body temperature ranges of an animal, metabolic rate, water loss, absorptivity (of radiation), diameter and thickness of insulation. PG demonstrate this analysis for a variety of ecto/endothermic animals of varying body size and insulation. In this way, the fundamental climatic niche of an animal can be estimated without having to experimentally assess animal survival across the entire range of climatic conditions we are interested in.

Deustch et al. 2007

Deustch et al. use data on ectotherm performance varies with temperature to make projections about how climate change will impact fitness. In their main analysis, they use experimental data population growth rate over different temperatures to compute thermal performance curves for insects across a wide latitudinal range. From the thermal performance curves and climate projections for 2100 they find that insects in low latitudes (tropics) will experience decreases in population growth rate while insects in higher latitudes will experience increase in population growth rate. These results are explained by their findings that the “warming tolerance,” the difference between the current temperature and maximum tolerable temperature is smaller for low-latitude vs higher latitude insects, which means that low-latitude insects are more sensitive to changes in temperature. Furthermore, the “thermal safety margin,” the difference between the optimal and current temperature for insect population growth is smaller for low-latitude species than higher-latitude species. This means that increased temperature will decrease the performance of low-latitude species whereas it will enhance the performance of higher-latitude species, since the thermal optima of higher-latitude species tends to be higher than current temperatures.

My thoughts

These papers both focus on how animal performance varies depends on abiotic factors. Porter and Gates seemed to be more focused on the basic task of defining and quantifying the fundamental climate niche of animals, whereas Deutsch et al. were more focused on applying what we now know about thermal performance to make forecasts about the impact of climate change. To me the most interesting aspects of these papers were their integration of existing or (somewhat) easily measurable physiological data with models to make predictions about niche requirements and performance. I think this approach highlights how models and data can be used to more mechanistic and, hopefully, more accurate predictions.