News Feature: Getting the world’s fastest cat to breed with speed | PNAS
(originally posted 16 Dec 2019)
Good evening all,
We've made it a point several times during class this term to highlight how behavioral knowledge could be applied to conservation efforts. Here's a link to a recent (and lengthy) discussion of how captive breeding in cheetahs has been enhanced by applying more-naturalistic methods than simply pairing together single males and females. It's quite striking the lengths to which breeders have gone in order to improve the success rate of their breeding programs!
https://www.pnas.org/content/116/50/24911
Dr. Nealen
(originally posted 16 Dec 2019)
Good evening all,
We've made it a point several times during class this term to highlight how behavioral knowledge could be applied to conservation efforts. Here's a link to a recent (and lengthy) discussion of how captive breeding in cheetahs has been enhanced by applying more-naturalistic methods than simply pairing together single males and females. It's quite striking the lengths to which breeders have gone in order to improve the success rate of their breeding programs!
https://www.pnas.org/content/116/50/24911
Dr. Nealen
New insights into genetic basis of bird migration | Penn State University
(originally posted 12 Dec 2019)
Good morning all,
Hot off of the presses - new information on the genetic basis of avian migratory behavior, a topic we have considered in class. Here, researchers believe that they have identified a single gene on one of the avian sex chromosomes that is linked to specific migratory targeting in warbler species of conservation concern. Interestingly, this avian gene is related to a human gene thought to be associated with movement.
This is a good example of the current state of much of the study between genetics and behavior. Through large-scale genomic analyses, it is possible to identify associations (correlations) between individual gene variants and particular aspects of behavior, but there is much to be learned "in the middle" - how does any one gene, and its gene product, mechanistically contribute to behavior? Or is the association identified in first-order analyses spurious, or non-causal? There is plenty of room for further work, as these researchers note.
https://news.psu.edu/story/585429/2019/08/28/research/new-insights-genetic-basis-bird-migration?utm_source=newswire&utm_medium=email&utm_content=12-12-2019&utm_campaign=research newswire
Good luck with all of your remaining exams -
Dr. Nealen
(originally posted 12 Dec 2019)
Good morning all,
Hot off of the presses - new information on the genetic basis of avian migratory behavior, a topic we have considered in class. Here, researchers believe that they have identified a single gene on one of the avian sex chromosomes that is linked to specific migratory targeting in warbler species of conservation concern. Interestingly, this avian gene is related to a human gene thought to be associated with movement.
This is a good example of the current state of much of the study between genetics and behavior. Through large-scale genomic analyses, it is possible to identify associations (correlations) between individual gene variants and particular aspects of behavior, but there is much to be learned "in the middle" - how does any one gene, and its gene product, mechanistically contribute to behavior? Or is the association identified in first-order analyses spurious, or non-causal? There is plenty of room for further work, as these researchers note.
https://news.psu.edu/story/585429/2019/08/28/research/new-insights-genetic-basis-bird-migration?utm_source=newswire&utm_medium=email&utm_content=12-12-2019&utm_campaign=research newswire
Good luck with all of your remaining exams -
Dr. Nealen
A Population of Billions May Have Contributed to This Bird’s Extinction - The New York Times
(originally posted 03 Dec 2019)
Hi folks,
As part of our discussions of sociality for Thursday, we'll need this short reading. It suggests that passenger pigeons, which once numbered in the billions, were driven to extinction over the course of a few decades in part because their large population size made them more at risk from extinction than if they had existed in smaller populations. This argument is directly counter to what we normally think of, in terms of how population size relates to extinction risk.
https://www.nytimes.com/2017/11/16/science/passenger-pigeons-extinction.html
The article references a piece of original scientific literature, linked here:
https://science.sciencemag.org/content/358/6365/951
Dr. Nealen
(originally posted 03 Dec 2019)
Hi folks,
As part of our discussions of sociality for Thursday, we'll need this short reading. It suggests that passenger pigeons, which once numbered in the billions, were driven to extinction over the course of a few decades in part because their large population size made them more at risk from extinction than if they had existed in smaller populations. This argument is directly counter to what we normally think of, in terms of how population size relates to extinction risk.
https://www.nytimes.com/2017/11/16/science/passenger-pigeons-extinction.html
The article references a piece of original scientific literature, linked here:
https://science.sciencemag.org/content/358/6365/951
Dr. Nealen
Evolution of sexual cooperation from sexual conflict | PNAS
(originally posted 21 Nov 2019)
Good morning all,
As I noted on Tuesday, we will not meet for lecture today. We have only one textbook chapter remaining, which we will save for our first meeting after the Thanksgiving break.
Instead of lecture today, I'll offer you a reading instead, one that encompasses several of our recent topics. In recent classes, we have considered the degree of cooperation and conflict between reproductive partners, as well as the signaling that occurs to influence each other. When sexual investment is strongly different between the sexes, we expect that sexual selection can drive exaggerated displays, enhance female 'choosiness' of mates, and promote unequal reproductive tactics. But, curiously, sexual displays also are common within pair-bonded species, in which males and females have equal (or nearly equal) roles and should be in cooperative agreement over parental investment, rather than in conflict. An explanation for this paradox has been lacking.
A very recent paper sheds some light on this problem, and present a mathematical model which supports the idea that inter-sexual signaling displays which originate to exploit a sensory bias in the signal receiver can evolve into a cooperative exchange, suggesting that sexual conflict can morph into sexual cooperation. This has significant implications for parental investment and care, as we've noted that the degree of sexual conflict is one of the primary drivers of sexual dimorphism in parental investment.
https://www.pnas.org/content/116/46/23225.abstract?etoc
This paper was published in the Proceedings of the National Academy of Science (PNAS), our national body of 'science experts'. Election to the Academy is reserved for the top thinkers in one's field, and is a prestigious badge of honor. Their Proceedings journal publishes papers submitted by Academy members, as well as those that Academy members recommend for publication.
If you access this link from an IUP campus computer, you can obtain access to the full article and its associated material, through IUP library subscription. If you try to access the article from off-campus, you will be blocked. I've attached the PDF of the article, just in case.
The math of the authors' model is well beyond us. If we accept their model as being sound, it suggests that, instead of females being 'lured' into over-investment in their offspring by male displays, females instead evolve to require (or at least benefit from) the male display in terms of stimulating female condition/motivation to a level of investment which is optimal for the female (but less than that which is maximally optimal for the male). This causes males to remain invested in the pair-bond and their role in parental investment, and reinforces the pair-bond between mating partners. In a sense, the females are now requiring the males to remain present, remain attentive, and to offer displays, in order to ensure that their female partner is providing enough investment of her own.
As do many science journal, PNAS occasionally offers peer commentary on papers which are especially important, or especially difficult (this one is perhaps both). The associated commentary on this paper (link below, PDF attached), describes this result in the context of dove mating pairs, for which male stimulation of female reproductive condition is a well-understood and very necessary component to the reproductive cycle. Interestingly, as the commentary notes, the capitulation of this male-female exchange may ultimately be female self-stimulation of reproductive condition, a result which has been suggested to occur in doves. That may be the current evolutionary end-point to this exchange, but it also has the potential to serve as a type of an "escape clause", which males may now be selected to exploit. It would be interesting to see how much variation exists in this end-point, and whether males can benefit from females which perform more of their own reproductive stimulation.
https://www.pnas.org/content/116/46/22899?etoc=
I hope that you find this article interesting - it represent a nice, theoretical treatment of a difficult (= interesting) problem, and should set the stage for experimental work to come.
I hope that you all have an excellent Thanksgiving break - please be safe, rest, relax, eat, and enjoy. See you early in December for our last chapter.
Sincerely,
Dr. Nealen
(originally posted 21 Nov 2019)
Good morning all,
As I noted on Tuesday, we will not meet for lecture today. We have only one textbook chapter remaining, which we will save for our first meeting after the Thanksgiving break.
Instead of lecture today, I'll offer you a reading instead, one that encompasses several of our recent topics. In recent classes, we have considered the degree of cooperation and conflict between reproductive partners, as well as the signaling that occurs to influence each other. When sexual investment is strongly different between the sexes, we expect that sexual selection can drive exaggerated displays, enhance female 'choosiness' of mates, and promote unequal reproductive tactics. But, curiously, sexual displays also are common within pair-bonded species, in which males and females have equal (or nearly equal) roles and should be in cooperative agreement over parental investment, rather than in conflict. An explanation for this paradox has been lacking.
A very recent paper sheds some light on this problem, and present a mathematical model which supports the idea that inter-sexual signaling displays which originate to exploit a sensory bias in the signal receiver can evolve into a cooperative exchange, suggesting that sexual conflict can morph into sexual cooperation. This has significant implications for parental investment and care, as we've noted that the degree of sexual conflict is one of the primary drivers of sexual dimorphism in parental investment.
https://www.pnas.org/content/116/46/23225.abstract?etoc
This paper was published in the Proceedings of the National Academy of Science (PNAS), our national body of 'science experts'. Election to the Academy is reserved for the top thinkers in one's field, and is a prestigious badge of honor. Their Proceedings journal publishes papers submitted by Academy members, as well as those that Academy members recommend for publication.
If you access this link from an IUP campus computer, you can obtain access to the full article and its associated material, through IUP library subscription. If you try to access the article from off-campus, you will be blocked. I've attached the PDF of the article, just in case.
The math of the authors' model is well beyond us. If we accept their model as being sound, it suggests that, instead of females being 'lured' into over-investment in their offspring by male displays, females instead evolve to require (or at least benefit from) the male display in terms of stimulating female condition/motivation to a level of investment which is optimal for the female (but less than that which is maximally optimal for the male). This causes males to remain invested in the pair-bond and their role in parental investment, and reinforces the pair-bond between mating partners. In a sense, the females are now requiring the males to remain present, remain attentive, and to offer displays, in order to ensure that their female partner is providing enough investment of her own.
As do many science journal, PNAS occasionally offers peer commentary on papers which are especially important, or especially difficult (this one is perhaps both). The associated commentary on this paper (link below, PDF attached), describes this result in the context of dove mating pairs, for which male stimulation of female reproductive condition is a well-understood and very necessary component to the reproductive cycle. Interestingly, as the commentary notes, the capitulation of this male-female exchange may ultimately be female self-stimulation of reproductive condition, a result which has been suggested to occur in doves. That may be the current evolutionary end-point to this exchange, but it also has the potential to serve as a type of an "escape clause", which males may now be selected to exploit. It would be interesting to see how much variation exists in this end-point, and whether males can benefit from females which perform more of their own reproductive stimulation.
https://www.pnas.org/content/116/46/22899?etoc=
I hope that you find this article interesting - it represent a nice, theoretical treatment of a difficult (= interesting) problem, and should set the stage for experimental work to come.
I hope that you all have an excellent Thanksgiving break - please be safe, rest, relax, eat, and enjoy. See you early in December for our last chapter.
Sincerely,
Dr. Nealen
Dog genes and behavior, revisited
(originally posted 24 Oct 2019)
Hi folks,
As I mentioned in lecture on Tuesday, we are caught-up with our lecture material and will not meet for lecture on Thursday. Instead, I am offering a reading (attached) that I had described earlier, along with some explanation of one of the more important points described in this study.
Last weekend, I sent to our class description (below) of a recent publication examining behavioral-genetic associations in domestic dogs. I hadn't yet seen the original research when I wrote to you last weekend, but forwarded a news report about it that came from the home institution of the senior author on the study. I described in my message to you that some of the behavioral-genetic associations the authors reported were as high as 0.7, near to the limit of those ever reported for narrow-sense heritabilities of behavior.
Over the weekend, I requested a copy of the actual research paper from its senior author, and, upon seeing it, wanted to offer some interpretation.
Early in the term, in chapter 03, we discussed trait variation within species, and we noted (using the canine example) that artificial selection has created an abnormally high amount of trait variation within the single species of domestic dog Canis lupus familiaris.
In our next lecture (Chapter 04), we discussed behavioral genetics and narrow-sense estimates of heritability, describing the upper limit of such associations as around 0.7. We saw in that same chapter (as well as in later chapters, including Chapter 10) some estimates of narrow-sense behavioral-genetic heritability estimates that all were < 0.3, which is typical.
In this new report, the authors report behavioral-genetic associations that are much higher than those typically reported. How can this be? It stems from the artificial (and unusually large) degree of trait variation within this domestic species.
Typically, when one examines associations between traits within a natural (e.g., not artificially-selected) species, we expect some small, defined range of trait values, with correlation (association) between traits of some relatively low magnitude. Here in my Figure 1, I show the trait values and the within-species bivariate trait association for two (hypothetical) different species, such as a fox and a wolf. Within either species, there is some defined range of values for trait X (such as body length) and some defined range of values for trait Y (such as body mass). In my hypothetical example, these traits are correlated somewhat weakly within species A, and uncorrelated within species B. Notice that the two species do not overlap in trait values - a small wolf is always larger than than a large fox.
If domestic dogs were a natural species, chances are good that their trait values would fall somewhere in between these two species, perhaps closer to the 'wolf' end of the spectrum. Nonetheless, they would be expected to occupy only a small potion of the overall trait ranges.
Now, consider what the authors have done in their analysis. They have considered all domestic dog breeds to be of the same species, a fact that is technically true but which ignores the other fact that their range of trait values is anything but normal. They have analyzed behavioral-genetic associations across breeds within this single species, but here the individual breeds represent much more trait variation than natural species might, as size variation across domestic dog breeds is much greater than size variation across canine species in the wild. When associations are evaluated across multiple species (such as in my hypothetical Figure 2), the associations are often of higher magnitude. In the current study, analysis across the very artificially-distributed dog breeds behaves in the same way, resulting in behavioral-genetic associations much higher that those reported within single, natural species. 13/14 of their within-breed estimates (their Figure 1) are <0.3, just as one would expect.
This study is quite interesting, and represent the application of some very modern techniques (canine SNP chip, anyone?) to this interesting question of the heritability of behaviors. It also serves as a very useful reminder of
- the power of artificial selection - modern dog breeds are estimated to have been developed only over the last 300-500 years. For a natural species to evolve as much trait variation in this short time is unheard of.
- the danger of reliance upon secondary news sources - the original news story that I sent to you accurately describes the gist of this research study, and highlights the very strong associations found. But, it also leaves out enough detail that it is not possible to immediately assess why the associations are of such magnitude.
- the importance of proper modeling of evolutionary constraint - as shown in my hypothetical example Figure 2, trait associations across species can be artificially inflated if simple, linear techniques are used instead of methods that account for shared evolutionary history, such as independent contrasts analysis or nested ANOVA. The authors do have a phylogenetic model for their dog breeds; I am not schooled well-enough in the jargon of their analytical models to know if they have fully controlled for relatedness. Whether they have, or have not, these types of broad comparisons should always be examined with an eye for that type of concern.
- the imperfection of any one study - this is a research report describing one body of work on this topic, and I'm certain we could find other, similar/related studies. Is this study perfect? Certainly not. Is it still interesting, and useful? Absolutely. Any one research study can only advance our understanding incrementally. It's too easy, and too common, to dismiss work outright for containing flaws - it's more important to ask, given such flaws, is there anything that we can learn? The latter approach is more fruitful, and provides a much better return on one's investment of time and effort. Here, the traits with the highest across-breed heritabilities are trainability, aggression, and attachment - exactly those traits we might expect to have been key in the artificial selection/shaping of the human-dog relationship. It's a nice confirmation that these are strongly heritable, in ways that have translated into very powerful differences among breeds.
I've spent perhaps too much time dissecting some of these points, but I do so because they put some of our lecture material into sharp relief. Textbook examples are often too carefully culled to represent cutting-edge investigation; it's both fun as well as useful to see where current researchers in these areas actually are working.
Have a great rest of the week - see you on Tuesday for Chapter 11.
Sincerely,
Dr. Nealen
(originally posted 24 Oct 2019)
Hi folks,
As I mentioned in lecture on Tuesday, we are caught-up with our lecture material and will not meet for lecture on Thursday. Instead, I am offering a reading (attached) that I had described earlier, along with some explanation of one of the more important points described in this study.
Last weekend, I sent to our class description (below) of a recent publication examining behavioral-genetic associations in domestic dogs. I hadn't yet seen the original research when I wrote to you last weekend, but forwarded a news report about it that came from the home institution of the senior author on the study. I described in my message to you that some of the behavioral-genetic associations the authors reported were as high as 0.7, near to the limit of those ever reported for narrow-sense heritabilities of behavior.
Over the weekend, I requested a copy of the actual research paper from its senior author, and, upon seeing it, wanted to offer some interpretation.
Early in the term, in chapter 03, we discussed trait variation within species, and we noted (using the canine example) that artificial selection has created an abnormally high amount of trait variation within the single species of domestic dog Canis lupus familiaris.
In our next lecture (Chapter 04), we discussed behavioral genetics and narrow-sense estimates of heritability, describing the upper limit of such associations as around 0.7. We saw in that same chapter (as well as in later chapters, including Chapter 10) some estimates of narrow-sense behavioral-genetic heritability estimates that all were < 0.3, which is typical.
In this new report, the authors report behavioral-genetic associations that are much higher than those typically reported. How can this be? It stems from the artificial (and unusually large) degree of trait variation within this domestic species.
Typically, when one examines associations between traits within a natural (e.g., not artificially-selected) species, we expect some small, defined range of trait values, with correlation (association) between traits of some relatively low magnitude. Here in my Figure 1, I show the trait values and the within-species bivariate trait association for two (hypothetical) different species, such as a fox and a wolf. Within either species, there is some defined range of values for trait X (such as body length) and some defined range of values for trait Y (such as body mass). In my hypothetical example, these traits are correlated somewhat weakly within species A, and uncorrelated within species B. Notice that the two species do not overlap in trait values - a small wolf is always larger than than a large fox.
If domestic dogs were a natural species, chances are good that their trait values would fall somewhere in between these two species, perhaps closer to the 'wolf' end of the spectrum. Nonetheless, they would be expected to occupy only a small potion of the overall trait ranges.
Now, consider what the authors have done in their analysis. They have considered all domestic dog breeds to be of the same species, a fact that is technically true but which ignores the other fact that their range of trait values is anything but normal. They have analyzed behavioral-genetic associations across breeds within this single species, but here the individual breeds represent much more trait variation than natural species might, as size variation across domestic dog breeds is much greater than size variation across canine species in the wild. When associations are evaluated across multiple species (such as in my hypothetical Figure 2), the associations are often of higher magnitude. In the current study, analysis across the very artificially-distributed dog breeds behaves in the same way, resulting in behavioral-genetic associations much higher that those reported within single, natural species. 13/14 of their within-breed estimates (their Figure 1) are <0.3, just as one would expect.
This study is quite interesting, and represent the application of some very modern techniques (canine SNP chip, anyone?) to this interesting question of the heritability of behaviors. It also serves as a very useful reminder of
- the power of artificial selection - modern dog breeds are estimated to have been developed only over the last 300-500 years. For a natural species to evolve as much trait variation in this short time is unheard of.
- the danger of reliance upon secondary news sources - the original news story that I sent to you accurately describes the gist of this research study, and highlights the very strong associations found. But, it also leaves out enough detail that it is not possible to immediately assess why the associations are of such magnitude.
- the importance of proper modeling of evolutionary constraint - as shown in my hypothetical example Figure 2, trait associations across species can be artificially inflated if simple, linear techniques are used instead of methods that account for shared evolutionary history, such as independent contrasts analysis or nested ANOVA. The authors do have a phylogenetic model for their dog breeds; I am not schooled well-enough in the jargon of their analytical models to know if they have fully controlled for relatedness. Whether they have, or have not, these types of broad comparisons should always be examined with an eye for that type of concern.
- the imperfection of any one study - this is a research report describing one body of work on this topic, and I'm certain we could find other, similar/related studies. Is this study perfect? Certainly not. Is it still interesting, and useful? Absolutely. Any one research study can only advance our understanding incrementally. It's too easy, and too common, to dismiss work outright for containing flaws - it's more important to ask, given such flaws, is there anything that we can learn? The latter approach is more fruitful, and provides a much better return on one's investment of time and effort. Here, the traits with the highest across-breed heritabilities are trainability, aggression, and attachment - exactly those traits we might expect to have been key in the artificial selection/shaping of the human-dog relationship. It's a nice confirmation that these are strongly heritable, in ways that have translated into very powerful differences among breeds.
I've spent perhaps too much time dissecting some of these points, but I do so because they put some of our lecture material into sharp relief. Textbook examples are often too carefully culled to represent cutting-edge investigation; it's both fun as well as useful to see where current researchers in these areas actually are working.
Have a great rest of the week - see you on Tuesday for Chapter 11.
Sincerely,
Dr. Nealen
Genes play a role in dog breed differences in behavior | Penn Today
(originally posted 20 Oct 2019)
Good morning all,
At several points this term, we have discussed the genetics of behavior, including both the ability of single genes to influence behavior, as well as the heritability of individual behaviors and how traits can potentially be mapped onto phylogenetic histories. In the recent behavioral news is a report of a study that used large databases on dog behavior and genetics to look for behavioral traits that were associated with consistent genetic features. The researchers found >100 potential sites in the genome that were strongly associated with dog breed characteristics, including train-ability, aggression, excitability, and others.
One of the strengths of the method used here was that the researchers restricted themselves to a subset of the data pertaining to purebred dogs. This has the advantage of eliminating cross-breed variation which could dilute the strength of the genetic signals they were trying to detect. Dogs also are an advantageous species for a study like this, because they are popular, have long been bred in relatively pure lines, and have been artificially selected for a range of behavioral characteristics.
Some of the associations reported are quite strong, with heritability estimates as high as 60-70%. Those are very high values, near the limit reported for animal behavior-genetic comparisons. It's also surprising, in that, while this study has several strengths in its design, it also has one specific weakness: the researchers did not have genetic and behavioral information from the same individual animals, but instead were relying on databases (and breed averages) assessed across different individuals. That suggests that some of the associations, if tested within individual subjects, could be even stronger.
https://penntoday.upenn.edu/news/genes-play-role-dog-breed-differences-behavior
The human-dog relationship is a long one, and our artificial selection of dogs has been enormously powerful - when you think about all of the different dog breeds in the world, from Danes to dachshunds, Newfoundlands to chihuahuas, they all are the same species. That is testament to an enormous phenotypic plasticity (reaction norm) within their development. I'm going to request a copy of the original research article that this news report references, if anyone would like to see it - I'll bet it is interesting reading. Perhaps it will shed some light on my dog's (a rescue Rottweiler) behavior...
Have a great rest of the weekend - see you on Tuesday.
Dr. Nealen
(originally posted 20 Oct 2019)
Good morning all,
At several points this term, we have discussed the genetics of behavior, including both the ability of single genes to influence behavior, as well as the heritability of individual behaviors and how traits can potentially be mapped onto phylogenetic histories. In the recent behavioral news is a report of a study that used large databases on dog behavior and genetics to look for behavioral traits that were associated with consistent genetic features. The researchers found >100 potential sites in the genome that were strongly associated with dog breed characteristics, including train-ability, aggression, excitability, and others.
One of the strengths of the method used here was that the researchers restricted themselves to a subset of the data pertaining to purebred dogs. This has the advantage of eliminating cross-breed variation which could dilute the strength of the genetic signals they were trying to detect. Dogs also are an advantageous species for a study like this, because they are popular, have long been bred in relatively pure lines, and have been artificially selected for a range of behavioral characteristics.
Some of the associations reported are quite strong, with heritability estimates as high as 60-70%. Those are very high values, near the limit reported for animal behavior-genetic comparisons. It's also surprising, in that, while this study has several strengths in its design, it also has one specific weakness: the researchers did not have genetic and behavioral information from the same individual animals, but instead were relying on databases (and breed averages) assessed across different individuals. That suggests that some of the associations, if tested within individual subjects, could be even stronger.
https://penntoday.upenn.edu/news/genes-play-role-dog-breed-differences-behavior
The human-dog relationship is a long one, and our artificial selection of dogs has been enormously powerful - when you think about all of the different dog breeds in the world, from Danes to dachshunds, Newfoundlands to chihuahuas, they all are the same species. That is testament to an enormous phenotypic plasticity (reaction norm) within their development. I'm going to request a copy of the original research article that this news report references, if anyone would like to see it - I'll bet it is interesting reading. Perhaps it will shed some light on my dog's (a rescue Rottweiler) behavior...
Have a great rest of the weekend - see you on Tuesday.
Dr. Nealen
These Butterflies Evolved to Eat Poison. How Could That Have Happened? - The New York Times
(originally posted 12 Oct 2019)
Good morning,
We've considered recently the concept of aposematism, the display of warning coloration to indicate to potential predators that one is unpalatable or otherwise unsuitable as a prey item. As we have seen, there are many implications to this type of signaling, including the costs involved, the degree to which it is effective, and its potential to be mimicked (and thus rendered potentially less effective) by palatable species.
The issue of aposematic costs is one that has been considered for some time, particularly the metabolic costs of producing warning coloration as well as the predation cost of being conspicuous. In addition to these are the metabolic costs of actually being unpalatable, and in no system has this been better explored than in monarch butterflies, conspicuous in both larval and adult forms, as well as highly unpalatable in each for the glycosidic compounds they acquire and sequester from milkweed plants (their near-exclusive forage). These compounds are highly toxic disruptors of Na+ channels, and being able to ingest and store them has required some evolutionary tinkering.
In the recent science news is consideration of this phenomenon, with some genetic work that explains the evolution of caterpillar resistance to these glycosides. The plant defenses have evolved to deter caterpillar feeding, but the caterpillars were able to evolve resistance with as few as three genetic mutations. These researchers were able to induce these same mutations in fruit flies, rendering them resistant to the glycosides as well - a very powerful experimental demonstration. The researchers also demonstrate some of the costs associated with the evolution of resistance to glycosides, including reduced ability to withstand physical shock. No evolutionary benefit is free, and beneficial changes to genes often are paired with deleterious side-effects. Here, the benefit (unpalatability) appears to outweigh the costs (reduced ability to withstand physical rotation).
Many of the plants and animals around us are conspicuous, while many others are cryptic. Those that are colorful and eye-catching may be silently playing potentially-deadly games of chemical warfare. Nature has been described as 'red in tooth and claw' (William Congreve); we might expand that to '... tooth, and claw, and toxin', for many toxins (including these glycosides) are quite deadly. What is remarkable to me is the role of simple sugars in glycosides, forming one side of the glycosidic bond. This is why some dangerous chemicals (such as automotive antifreeze, ethylene glycol) taste sweet and thus are dangerously attractive to the uninitiated. It makes me wonder whether glycosides have ever been used in nature as deadly bait, to lure, and then poison, potential prey. I'm willing to bet that it has...
https://www.nytimes.com/2019/10/02/science/monarch-butterflies-milkweed.html
Have a great weekend-
Dr. Nealen
(originally posted 12 Oct 2019)
Good morning,
We've considered recently the concept of aposematism, the display of warning coloration to indicate to potential predators that one is unpalatable or otherwise unsuitable as a prey item. As we have seen, there are many implications to this type of signaling, including the costs involved, the degree to which it is effective, and its potential to be mimicked (and thus rendered potentially less effective) by palatable species.
The issue of aposematic costs is one that has been considered for some time, particularly the metabolic costs of producing warning coloration as well as the predation cost of being conspicuous. In addition to these are the metabolic costs of actually being unpalatable, and in no system has this been better explored than in monarch butterflies, conspicuous in both larval and adult forms, as well as highly unpalatable in each for the glycosidic compounds they acquire and sequester from milkweed plants (their near-exclusive forage). These compounds are highly toxic disruptors of Na+ channels, and being able to ingest and store them has required some evolutionary tinkering.
In the recent science news is consideration of this phenomenon, with some genetic work that explains the evolution of caterpillar resistance to these glycosides. The plant defenses have evolved to deter caterpillar feeding, but the caterpillars were able to evolve resistance with as few as three genetic mutations. These researchers were able to induce these same mutations in fruit flies, rendering them resistant to the glycosides as well - a very powerful experimental demonstration. The researchers also demonstrate some of the costs associated with the evolution of resistance to glycosides, including reduced ability to withstand physical shock. No evolutionary benefit is free, and beneficial changes to genes often are paired with deleterious side-effects. Here, the benefit (unpalatability) appears to outweigh the costs (reduced ability to withstand physical rotation).
Many of the plants and animals around us are conspicuous, while many others are cryptic. Those that are colorful and eye-catching may be silently playing potentially-deadly games of chemical warfare. Nature has been described as 'red in tooth and claw' (William Congreve); we might expand that to '... tooth, and claw, and toxin', for many toxins (including these glycosides) are quite deadly. What is remarkable to me is the role of simple sugars in glycosides, forming one side of the glycosidic bond. This is why some dangerous chemicals (such as automotive antifreeze, ethylene glycol) taste sweet and thus are dangerously attractive to the uninitiated. It makes me wonder whether glycosides have ever been used in nature as deadly bait, to lure, and then poison, potential prey. I'm willing to bet that it has...
https://www.nytimes.com/2019/10/02/science/monarch-butterflies-milkweed.html
Have a great weekend-
Dr. Nealen
‘Crypt keeper’ wasps, and echolocating humans
(originally posted 05 Oct 2019)
Good morning everyone,
In the recent science news are articles related to several of the topics we have considered recently - this is a nice confirmation that our course topics are 'up-to-date'!
Early in the term we considered the behavior of parasitic wasps, that stun prey and then oviposit eggs within them so that their larvae have a ready food supply during early growth. In the news this week is description of a different kind of parasitic wasp, one which parasitizes other wasps.
Here, the form of parasitism is less direct, in that the parasite deposits its eggs into the same plant gall that its host occupies. The parasite larvae then can attack the host, and in doing so, they accomplish a form of behavioral and physiological 'hypermanipulation'. Not only do they use the host tissues for their own nourishment, but they actually trigger a malformed version of the hosts normal escape behavior, which ensures that the host itself doesn't escape the gall but which provides the parasite an escape route.
https://www.sciencemag.org/news/2019/09/crypt-keeper-wasp-brainwashes-far-more-victims-thought
https://www.nytimes.com/2019/09/27/science/crypt-keeper-wasps-parasitic.html
https://www.bbc.com/news/science-environment-49692974
The degree to which parasites manipulate their hosts can be extraordinary. We are used to thinking that parasites can make use of host tissues, but examples like this reveal more complicated interactions, with some parasites hijacking host behavior as well. There are plenty of examples, such as these:
https://www.nationalgeographic.com/news/2018/10/141031-zombies-parasites-animals-science-halloween/
All are good reminders that host behavior, as well as host tissues, can be exploited by parasites.
Even more recently, I sent you some information about humans who have developed some ability to perform echolocation. Just this week came a report on this topic, suggesting real, functional remapping of the brain's visual cortex to support this new capability:
https://www.sciencemag.org/news/2019/10/echolocation-blind-people-reveals-brain-s-adaptive-powers
At some level, neural plasticity is responsible for all that we can learn, but to have whole-scale re-functioning of a part of the brain from one sense to another is very impressive.
Have a good weekend -
Dr. Nealen
(originally posted 05 Oct 2019)
Good morning everyone,
In the recent science news are articles related to several of the topics we have considered recently - this is a nice confirmation that our course topics are 'up-to-date'!
Early in the term we considered the behavior of parasitic wasps, that stun prey and then oviposit eggs within them so that their larvae have a ready food supply during early growth. In the news this week is description of a different kind of parasitic wasp, one which parasitizes other wasps.
Here, the form of parasitism is less direct, in that the parasite deposits its eggs into the same plant gall that its host occupies. The parasite larvae then can attack the host, and in doing so, they accomplish a form of behavioral and physiological 'hypermanipulation'. Not only do they use the host tissues for their own nourishment, but they actually trigger a malformed version of the hosts normal escape behavior, which ensures that the host itself doesn't escape the gall but which provides the parasite an escape route.
https://www.sciencemag.org/news/2019/09/crypt-keeper-wasp-brainwashes-far-more-victims-thought
https://www.nytimes.com/2019/09/27/science/crypt-keeper-wasps-parasitic.html
https://www.bbc.com/news/science-environment-49692974
The degree to which parasites manipulate their hosts can be extraordinary. We are used to thinking that parasites can make use of host tissues, but examples like this reveal more complicated interactions, with some parasites hijacking host behavior as well. There are plenty of examples, such as these:
https://www.nationalgeographic.com/news/2018/10/141031-zombies-parasites-animals-science-halloween/
All are good reminders that host behavior, as well as host tissues, can be exploited by parasites.
Even more recently, I sent you some information about humans who have developed some ability to perform echolocation. Just this week came a report on this topic, suggesting real, functional remapping of the brain's visual cortex to support this new capability:
https://www.sciencemag.org/news/2019/10/echolocation-blind-people-reveals-brain-s-adaptive-powers
At some level, neural plasticity is responsible for all that we can learn, but to have whole-scale re-functioning of a part of the brain from one sense to another is very impressive.
Have a good weekend -
Dr. Nealen
Chimps May Be Capable of Comprehending the Minds of Others - Scientific American
(originally posted 24 Sep 2019)
Hi folks,
Our next chapter (for Thursday) covers learning and cognition in animals, and I wanted to offer a couple of supplemental readings to accompany the material in our text. Our textbook describes a bit about the extent to which our closest relatives (the other members of the "great ape" lineage) may possess mental faculties approaching our own, and these two readings expand upon that idea, with the caveat that we may not also know how to best test, or interpret, animal behaviors.
The first reading describes some of the work done by researchers at Kyoto University, which houses a rich group of researchers in primate cognition. This report describes an attempt to interpret the mental states of chimpanzees, based upon their reaction to stimuli. If animals possess the capacity for thoughts and behaviors related to traits like empathy, jealousy, or disbelief, we can predict that they may respond in specific ways to certain kinds of stimuli. It's a challenging argument, to be sure, but many in the primate community believe that our closest primate relatives share more of our "higher" cognitive abilities than many would care to admit.
https://www.scientificamerican.com/article/chimps-may-be-capable-of-comprehending-the-minds-of-others/
The second reading is from a prominent primate behaviorist (Frans de Waal), who has long argued that we approach animal behavior too simplistically, and often erroneously. Taken to an extreme, he suggests that, at least at times, we are testing the wrong things and making interpretations that are illogical. I do not believe that his interpretations are widely held by members of the behavioral community, but they do serve as a useful reminder that we often make too many assumptions in our design and interpretation of behavioral experiments.
https://www.wsj.com/articles/SB10001424127887323869604578370574285382756
When we delve into Chapter 07 on Thursday, it will be useful to keep these viewpoints in mind.
See you this afternoon for collection of exam corrections. We'll have time to review and discuss any material we wish to cover today.
Sincerely,
Dr. Nealen
(originally posted 24 Sep 2019)
Hi folks,
Our next chapter (for Thursday) covers learning and cognition in animals, and I wanted to offer a couple of supplemental readings to accompany the material in our text. Our textbook describes a bit about the extent to which our closest relatives (the other members of the "great ape" lineage) may possess mental faculties approaching our own, and these two readings expand upon that idea, with the caveat that we may not also know how to best test, or interpret, animal behaviors.
The first reading describes some of the work done by researchers at Kyoto University, which houses a rich group of researchers in primate cognition. This report describes an attempt to interpret the mental states of chimpanzees, based upon their reaction to stimuli. If animals possess the capacity for thoughts and behaviors related to traits like empathy, jealousy, or disbelief, we can predict that they may respond in specific ways to certain kinds of stimuli. It's a challenging argument, to be sure, but many in the primate community believe that our closest primate relatives share more of our "higher" cognitive abilities than many would care to admit.
https://www.scientificamerican.com/article/chimps-may-be-capable-of-comprehending-the-minds-of-others/
The second reading is from a prominent primate behaviorist (Frans de Waal), who has long argued that we approach animal behavior too simplistically, and often erroneously. Taken to an extreme, he suggests that, at least at times, we are testing the wrong things and making interpretations that are illogical. I do not believe that his interpretations are widely held by members of the behavioral community, but they do serve as a useful reminder that we often make too many assumptions in our design and interpretation of behavioral experiments.
https://www.wsj.com/articles/SB10001424127887323869604578370574285382756
When we delve into Chapter 07 on Thursday, it will be useful to keep these viewpoints in mind.
See you this afternoon for collection of exam corrections. We'll have time to review and discuss any material we wish to cover today.
Sincerely,
Dr. Nealen
Just like bats, humans can use echolocation
(originally posted 21 Sep 2019)
Good morning all,
We recently considered bat echolocation as a model for sensory coevolution. During our discussions, we noted that many animals have sensory capabilities outside of the range of humans.
How about humans who can perform echolocation?
https://phys.org/news/2018-04-humans-echolocation.html
There are a small number (few dozen) people in the world who have developed some level of proficiency at echolocation for navigation. Daniel Kish is the most famous person with these abilities (but there are others):
https://www.youtube.com/watch?v=A8lztr1tu4o
In all of these cases, the ability came about after a loss of vision. Our human visual cortices make up a huge part of our brains, and once they are freed from visual responsibilities, it seems that they can be co-opted (at least in part) for other uses. This neural flexibility is well-known, as it is the basis for the recovery that is possible from brain trauma, including stroke. Blind persons who read Braille are known to have some expanded touch sensitivity in visual areas of the brain, and sensory re-mapping is known to occur in persons with high-levels of musical training, or in new mothers nursing infants. Still, the development of echolocation as a sensory capability is quite different, in that it adds to the human sensory repertoire, not simply expands upon an existing sense.
There are lots of interesting articles about human echolocation, including:
https://www.sciencealert.com/humans-can-echolocate-like-bats-and-whales-and-we-ve-finally-figured-out-how-it-works
https://www.livescience.com/39231-humans-can-learn-to-echolocate.html
https://www.newscientist.com/article/2145962-this-is-how-some-blind-people-are-able-to-echolocate-like-bats/
Next time you find yourself in a dark room, you might be tempted to give it a try! I think that I will stay close to the light switch...
Have a great weekend -
Dr. Nealen
(originally posted 21 Sep 2019)
Good morning all,
We recently considered bat echolocation as a model for sensory coevolution. During our discussions, we noted that many animals have sensory capabilities outside of the range of humans.
How about humans who can perform echolocation?
https://phys.org/news/2018-04-humans-echolocation.html
There are a small number (few dozen) people in the world who have developed some level of proficiency at echolocation for navigation. Daniel Kish is the most famous person with these abilities (but there are others):
https://www.youtube.com/watch?v=A8lztr1tu4o
In all of these cases, the ability came about after a loss of vision. Our human visual cortices make up a huge part of our brains, and once they are freed from visual responsibilities, it seems that they can be co-opted (at least in part) for other uses. This neural flexibility is well-known, as it is the basis for the recovery that is possible from brain trauma, including stroke. Blind persons who read Braille are known to have some expanded touch sensitivity in visual areas of the brain, and sensory re-mapping is known to occur in persons with high-levels of musical training, or in new mothers nursing infants. Still, the development of echolocation as a sensory capability is quite different, in that it adds to the human sensory repertoire, not simply expands upon an existing sense.
There are lots of interesting articles about human echolocation, including:
https://www.sciencealert.com/humans-can-echolocate-like-bats-and-whales-and-we-ve-finally-figured-out-how-it-works
https://www.livescience.com/39231-humans-can-learn-to-echolocate.html
https://www.newscientist.com/article/2145962-this-is-how-some-blind-people-are-able-to-echolocate-like-bats/
Next time you find yourself in a dark room, you might be tempted to give it a try! I think that I will stay close to the light switch...
Have a great weekend -
Dr. Nealen
CIA unveils Cold War spy-pigeon missions - BBC News
(originally posted 14 Sep 2019)
Good morning everyone,
In my scans of the science news, I often come across articles that overlap with our course topics. I'll share some of these with you, in the hopes that you find them interesting, and with a goal of broadening our conversations.
Today's news comes from a report about animal-based espionage, via training programs conducted by the CIA during the height of the Cold War. Animals are often highly adept at trained behaviors, and instinctual behaviors (like homing) can be co-opted for specialized tasks. Still, this report suggests that there was little direct benefit from these programs - or, perhaps they are not telling us everything, as much remains classified.
So, the next time you see a pigeon, cat, or dolphin(!) nearby, remember: they may be watching you as well...
https://www.bbc.com/news/world-us-canada-49692534
Have a great weekend -
Dr. Nealen
(originally posted 14 Sep 2019)
Good morning everyone,
In my scans of the science news, I often come across articles that overlap with our course topics. I'll share some of these with you, in the hopes that you find them interesting, and with a goal of broadening our conversations.
Today's news comes from a report about animal-based espionage, via training programs conducted by the CIA during the height of the Cold War. Animals are often highly adept at trained behaviors, and instinctual behaviors (like homing) can be co-opted for specialized tasks. Still, this report suggests that there was little direct benefit from these programs - or, perhaps they are not telling us everything, as much remains classified.
So, the next time you see a pigeon, cat, or dolphin(!) nearby, remember: they may be watching you as well...
https://www.bbc.com/news/world-us-canada-49692534
Have a great weekend -
Dr. Nealen
Hanging Out With Humans Makes This Bird Bad at Its Job - The New York Times
(originally posted 09 Sep 2019)
Good morning all,
Just passing along here an interesting news article, linking behavior and conservation.
Human have long associated with animals, and in doing so have shaped many of their behaviors. Here's an example of a detrimental effect: a semi-domestication that changes foraging behavior and seed dispersal in endangered New Zealand weka:
https://www.nytimes.com/2019/08/29/science/weka-birds-seeds-new-zealand.html
This kind of change illustrates the behavioral flexibility many species employ, particularly for adapting their own ecology to exploit the humans around them. In the long run, these sorts of associations can cause evolutionary change in brain and behavior (https://www.nationalgeographic.com/animals/2019/09/humans-shaped-dog-brains/), in ways that can dramatically alter the natural ecology of species. This is also an important reminder that interacting too much with endangered species can endanger them ever more if they imprint too strongly on humans - hence the need for 'panda suits' (https://www.youtube.com/watch?v=GaLP6S9ZHQ4 - how's that for a day job?).
See you tomorrow for review of the material for our first exam. I'm not planning a formal lecture; instead, I will review any material on which you have questions.
Sincerely,
Dr. Nealen
(originally posted 09 Sep 2019)
Good morning all,
Just passing along here an interesting news article, linking behavior and conservation.
Human have long associated with animals, and in doing so have shaped many of their behaviors. Here's an example of a detrimental effect: a semi-domestication that changes foraging behavior and seed dispersal in endangered New Zealand weka:
https://www.nytimes.com/2019/08/29/science/weka-birds-seeds-new-zealand.html
This kind of change illustrates the behavioral flexibility many species employ, particularly for adapting their own ecology to exploit the humans around them. In the long run, these sorts of associations can cause evolutionary change in brain and behavior (https://www.nationalgeographic.com/animals/2019/09/humans-shaped-dog-brains/), in ways that can dramatically alter the natural ecology of species. This is also an important reminder that interacting too much with endangered species can endanger them ever more if they imprint too strongly on humans - hence the need for 'panda suits' (https://www.youtube.com/watch?v=GaLP6S9ZHQ4 - how's that for a day job?).
See you tomorrow for review of the material for our first exam. I'm not planning a formal lecture; instead, I will review any material on which you have questions.
Sincerely,
Dr. Nealen