Pigeons are normally a heterosexual and monogamous species (the exception proves the rule). But what happens if you skew the sex ratio to more female-biased or male-biased? Łukasz Jankowiak, et al. (2018) did such experiments and found out that same-sex pairs can occur in such situations. It is known that female-same-sex pairs have a higher likelihood in monogamous species compared to polygamous species. In contrast, male-same-sex pairs are more likely in polygamous species. Indeed, this trend is supported by the experiment, which showed that there are more female-female pairings in a female-biased sex ration as male-male pairings in male-biased sex ratios. Moreover, the female-female partnerships were longer lasting and resulted in successful breeding whereas the male-male partnerships where short and showed no egg adoption behavior. Unfortunately, it is hard to find driving force behind same-sex pairs: there are many different theories (from mistaken sex identity to intersexual conflicts). The authors guess, that in this pigeon experiments, the same-sex pairing in males can be explained by the "heterosexual deprivation" (meaning: there are just no females available, therefore they go for males), while the female-female pairs are more driven by "alloparenting" (you need two adults for successful breeding so you better "bind" a female to your nest as breeding alone). But of course, it is just a guess. So message of the day: female-female pairs more in monogamous species, male-male pairs more in polygamous species. According to the paper, it has something to do with parental care: when the male provides a lot of parental care in monogamous species, females tend to compensate missing males with females, while males show a smaller chance of male-male pairing. In contrast, in polygamous species, if the males care less, the females do not have to compensate the missing men (less female-female pairs) while the frequency of male-male pairs increases.
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journals.plos.org/plosone/article?id=10.1371/journal.pone.0191456"Revisiting facial resemblance in couples."
Yetta Kwailing Wong, et al. PloS one 13.1 (2018): e0191456. They are "flying" in the polar seas: sea-butterflies are actually sea snails with a characteristic way of movement which looks like flapping wings. Limacina helicina is one of them, and scientists were worried about their future. The increased CO2 uptake into ocean waters leads to an acidification of the ocean water and diminishes the availability of carbonate ions which are important for making calcification of shells and skeletons. That means that if the periostracum (a sort of protection layer) is destroyed e.g. by failed predation attempts, the acid (carbonate undersaturated) water causes shell dissolution. But there are good news: Victoria L. Peck et al. (2018) showed that despite their original shell was partly dissolved, individuals of Limacina helicina were able to compensate that by thickening the inner shell wall. That does not mean, that acidification of the oceans is no problem! The thickening of the inner shell wall comes with a likely metabolic cost for the small sea-butterfly. It just means that these small animals have a higher tolerance as previously expected. I learned in school that in the 14. century the “Black Death” plague was caused by the bacterium Yersinia pestis which was transmitted by rat fleas. However, this may not be true. So yes, plague is caused by Yersinia pestis, but there are different infection ways: (I) from rat fleas to human, (II) from human ectoparasites (fleas and lice) to human and (III) from human to human by inhalation from infected droplets. But how you can find out many centuries later which infection way was the basis for the “Black Death”? The answer is: with mathematical models! Katharine R. Dean, et al. (PNAS 2018) created mathematical models for all three infection ways. So they were able to simulate how infection rates would develop over time for each type of infection. Then they fitted the simulation results to real outbreak data and showed that in many cases the “human ectoparasites to human” model fits best. Of course, it can still be that it was a mixture of different infection ways and that the main infection way differed from region to region. Nevertheless, it shows that the story which we learn in school, that the plague is caused by infected rats and rat fleas, is maybe too easy. There are people who fear robots taking over our lives. But it is not only human life in which robots will play a more and more prominent role. Also, lab animal life changes because of robotics. The field of "ethorobotics" grows: more and more experiments use robots to trigger and analyze certain behavioral responses of their study object. The paper of Kim et al. (2018) mentions robot studies which examine e.g. honeybee dance communication, bird courtship, fish schooling and the social behavior of rats. So the idea is to put a robot which simulates a certain behavior and look how living organisms are reacting to it. Many of these studies use “open-loop control”: the behavior of robot is pre-programmed and can not respond to the behavior of the live object. In contrast, “closed-loop control” systems allow the robot to interact in real-time with live subjects based on feedback from the animal behavior. Kim et al. developed a "closed-loop control" system in which a robotic arm moves a 3D printed zebra-fish replica in response to the behavior of a living zebrafish in its 3D water environment. They were able to show, that when replica and living original are in separate tanks which allow the zebrafish to watch the movement of the robot, the zebrafish seeks the closeness of the replica more often when its movement in one direction (y-axis) is closed-loop controlled compared to a complete open-loop controlled system. The increased shoaling time can be interpreted as an improved degree of biomimicry. Unfortunately, full 3D closed-loop control did not increase the replica performance. Kim et al. argue that this could be because of the increased probability of the replica to crash against the wall when all 3 axes are controlled by the living behavior. Maybe that wall crashing was interpreted as aggressive behavior and therefore induced avoidance behavior in the living fish. So the system is maybe not perfect yet, but it shows a new interactive robotics-based approach for zebrafish behavioural phenotyping in 3D . Imagine a world without blood-sucking mosquitos! So no itching red spots on your skin anymore and the global spread of mosquito-borne viruses such as Malaria, Zirka and dengue fever would be stopped. Before you start to discuss that there are e.g. birds which depend on mosquito as their favorite meal, allow me to clarify: I don't talk about killing the mosquito, I am talking about to transform it to a non-biting, friendly insect, which cannot harm us. I read an interesting commentary from Peter A. Armbruster (PNAS, 2018) which deals with the paper from Bradshaw et al. (PNASm 2017) in which they analyze which genes make the difference between biting an non-biting mosquito. Fun fact: There are already non-biting mosquito species in nature, and they evolved from biting ancestors multiple times independently. Non-biting can be an evolutionary benefit because even if blood provides energy and nutrition, it also comes with some costs: you need to spend energy on finding a host and you have to survive the feeding. Moreover, blood-feeding can elicit a protective heat-shock response and produces toxic by-products that must be taken care of. So no wonder that some mosquito species prefer not to bite. They build on resources which they collected in their larval state. So back to the work from Bradshaw et al. : They analyzed which genes make the difference between biting and non-biting mosquito. For that, they used W. smithii which is the only known mosquito species in which some populations are biting while other geographically disparate and genetically distinct populations are non-biters. Artificial selection experiments and comparing individuals from both populations show that there is indeed a pool of genes which seem to be different between biting and non-biting mosquito. Of course, they do not know yet the function of all the genes. But the idea of just manipulating the genetics of mosquito in order to reprogram them to non-biting species is scary amazing, isn't it? A large variety of life exists on earth. Biologists sort this biodiversity in a hierarchical system of taxonomic ranks: species, genus, family and so on. Interestingly, “at any taxonomical level, a very small number of units have a very large number of subunits, e.g., individuals per species, or genera per family, followed by a very rapid dropoff, resulting in what is commonly called a hollow curve distribution.” (Beres, et al. 2005). How does this unequal distribution evolve? Normally, when we talk about evolution and origin of biodiversity, we think about “survival of the fittest”, and mutations which help to adapt to different niches, … . However, in order to reproduce the hollow curve distribution (with mathematical models) you don’t need to assume differences in fitness and survival rate. The so called (Hubbell’s) “unified neutral theory of biodiversity” assumes that death and reproduction rates is independent from individual’s species and its neighbourhood. You fix the amount of individuals for an area (“zero-sum” assumption). The individuals can belong to different species. Every time step you pick randomly on of the individuals which has to die. At the same time you choose randomly on of the individuals who reproduces itself to fill the new gap. Moreover, there is a chance that the new individual evolves to a new species which balances random extinction and allows the number of species to stabilise. Of course there are different versions of that theory, more or less complicated, which were fitted to different datasets describing distributions e.g. of tree or coral species. But I want to point out (and what fascinates me about this topic) is that these simple assumptions/rules are all you do not need in order to reproduce the measured hollow curve distributions: No survival of the fittest but simple random events of death and reproduction and some mutations. Egbert G Leigh Jr. et al. (2010), Scholarpedia, 5(11):8822.
"The unified neutral theory of biodiversity and biogeography at age ten." James Rosindell, Stephen P. Hubbell, and Rampal S. Etienne. Trends in ecology & evolution 26.7 (2011): 340-348. "Rotifers and Hubbell's unified neutral theory of biodiversity and biogeography." Karl A. Beres, Robert L. Wallace, and Hendrik H. Segers. Natural Resource Modeling 18.3 (2005): 363-376. We all know that kind of guessing games: How many candies are in this jar? Which weight has this cow? The question is how you can improve your guess and maybe win the prize. In 1906, Sir Francis Galton noticed that the aggregate judgement of the players, the average of their estimates, closely approximated the true value. This is called the wisdom of crowds. So of course, a good method to win is to form a small group, take the average of the estimates, and share the win in the end. But what to do if you don't want to share? One possibility is that you ask yourself multiple times and take the average of your guesses. This is called the wisdom of the inner crowd. That works best if you let some time pass between the guesses or if your short-term memory is not the best and you tend to forget fast what you guessed before. Unfortunately, there is still a large chance that you will be beaten by any 2-person team. As the paper of Dennie van Dolder and Martijn van den Assem (2017) points out: "The average of a large number of judgements from the same person is barely better than the average of two judgements from different people". So the message of the day: Ask the others and learn to share! Life as a female moth is hard. Sitting alone in the dark, you are listening to the ultrasonic sounds of the night. Is this the attractive call of a male moth? If so, go ahead and make some love. But be careful. Bats are out there. You can hear their ultrasonic sounds which they use for echolocation. So you should be sure that the singing male moth is worth the risk. Is it the Romeo of your dreams or just a little wimp? The answer lies in the song, the environment temperature and your perception. The lesser wax moth (Achroia grisella) belongs to the group of insects which choose their partner mainly by their acoustic performance, like you know it from crickets and grasshoppers. A healthy male moth is supposed to produce louder songs with higher frequencies, compared to his old/weak rivals. However, there is the problem of the environmental temperature which can make the process of finding a partner a little bit more tricky. As cold blooded animals, the muscle performance of the male (and so its song quality) is enhanced with increasing temperatures. Therefore, in grasshoppers, not only the male song changes with increasing temperature but also the preferred song of the female is temperature dependent. This temperature coupling of “producer” and “receiver” ensures that the female is able to identify the males of the right species at different temperatures. (Here I would like to refer to the great work of my former colleague F.A. Römschied https://elifesciences.org/articles/02078 ). But is this temperature coupling, which can be found in many different acoustic species, really the result of the evolutionary need to find the right partner or is it just a lucky coincidence, that the female perception changes with temperature? This is the question of a paper from Greefield and Medlock in 2007. They point out that temperature coupling just makes sense when you (1) have a narrow range of “attractive songs” for females which selects against faster and slower rates and you (2) have other acoustic species around, which you have to distinguish. Therefore, in their paper, they focus on the lesser wax moth, which does not fulfill these criteria. Female moth prefer any songs above a certain frequency and their habitat is lacking any other acoustic species (besides the bats with low frequency sounds). Moreover, the female acceptance threshold for acceptance is much lower than the male song rates. Therefore, temperature effects on male song rates does not conflict with the moth concept of “the fastest and loudest song is the most attractive one”. Nevertheless, male song rate and female acceptance threshold do exhibit parallel increases with elevated temperature. But why, when there is no evolutionary benefit? Greefield and Medlock show that male and female thermal effects are genetically correlated. Of course that genetic coupling could be there, because evolution selected for parallel temperature effects in female and male. However, as evolutionary benefit of thermal coupling is hard to explain in this case, it could also be, that the thermal coupling is just a coincidence because the same genes can control different properties in different tissues like the song production with the wings in the male and the song perception in the female. So the main message of the paper is, that when there is thermal coupling between the sexes, you should not automatically assume that it is based on an evolutionary need to adapt sound and sound preference but it could also just be that sound production and sound perception are two temperature dependent processes which are controlled by the same genes. |
IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
März 2018
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