Date Published: January 30, 2015

Source:                 PLOS Biology

Authors:              Timo Ernst, Suzi McCarthy, Glenys Chidlow, Dagwin Luang-Suarkia, Edward C. Holmes, David W. Smith, Allison Imrie

Summary:           A study reveals the emergence of a new lineage of DENV (Dengue Virus) from returning travelers to Australia from Indonesia.

Dengue is the most rapidly spreading viral disease among humans. It’s endemic to most tropical and sub-tropical countries and causes an estimated 390 million infections to occur every year. Most of the disease burden is borne by people of Southeast Asia and the Western Pacific region. Understanding how the dengue moves from country to country and how it changes is vital to understand how to solve the problem. However, the data required to do such an analysis was lacking, thus limiting the attempts the scientists made to understand the hyperendemicity of the virus and its severity.

The authors of the study sequenced the E gene of DENV (Dengue Virus) that was isolated from travelers travelling to West Australia from 7 countries throughout Asia. The collected these samples and sequenced the genes over a span of two years from 2010-2012. The authors found that a majority of the virus originated in Indonesia which is a popular travel destination for Australians. They identified the hyperendemic transmission of all four DENV stereotypes in Indonesia in 2010. The Dengue is caused by infection with any one of these four stereotypes. The genotypes of these stereotypes can lead to lineages that either turnover, displace or introduce new lineages that can also cause dengue. The authors explained how it is important to track these changes and novel appearances since they are associated with a severe disease.

After having done the research, the authors found that a new lineage had emerged. This variation DENV2, or the cosmopolitan genotype, had appeared among travelers returning to Australia from other southeastern Asian countries. The introduction of this new genotype to the new populations of humans was caused by transmission. The new genotype was introduce due to mutations. The authors found that this new lineage originated in Bali in Indonesia. In the end, the authors discussed how due to a dearth of information regarding DENV from countries like Indonesia regarding sequenced genotypes, they weren’t able to determine when the new lineage emerged or whether it was present in another form in other countries before 2012. However, the concluded saying that surveilling returning travelers that are ill can help determine where the illness originate from.

This study shows a prime example of evolution happening on the smallest scales which have an astounding effect on a larger scale. The emergence of a new lineage of a certain virus through mutations shows the most basic form of evolution. This new lineage of DENV shows that it is being selected for among many possible mutated forms of DENV.

Citation:              Ernst T., S. McCarthy, G. Chidlow, D. Luang-Suarkia, E. C. Holmes, D. W. Smith, and A. Imrie. 2015. Emergence of a New Lineage of Dengue Virus Type 2 Identified in Travelers Entering Western Australia from Indonesia, 2010-2012. PLOS Neglected Tropical Diseases 9: e0003442.

Tick Tock: The Role of Circadian Clocks in Reproductive Shut Down for Northern House Mosquitoes

Date Published: February 1, 2015

Source: The Journal of Experimental Biology

Summary: A study was conducted to investigate how the effects of day length on the Culex pipiens' circadian clock components trigger their diapause.

The Northern house mosquito, Culex pipiens, faces a reproductive shut down during the winter time. This "reproductive shut down" that occurs is also known as diapause and it occurs when the amount of time the day lasts reaches a certain length – which in the case of C. pipiens occurs during the winter time. And after shutting down during the winter, C. pipiens resume their reproductive activity in the spring.

The cause of diapause has been researched in the past in numerous other species. This previous research has proved that circadian clocks, an internal clock that is in rhythm with daylight and darkness of the night, regulates body function within many organisms. In C. pipiens however, no definitive explanation to prove what particular mechanism helps these mosquitoes in measuring the day length and how that data triggers diapause is unknown. Megan Meuti from The Ohio State University and her colleagues: Mary Stone, Tomoko Ikeno, and David Denlinger studied C. pipiens to prove how their circadian clocks are affected by day length. Along with proving the role of circadian clocks, the team noted that C. pipiens are also carriers for deadly diseases. And with the discovery of what mechanisms trigger diapause, the team hopes to prevent disease transmission by controlling the mosquitoes' reproductive activity. 

To prove their hypothesis, the researchers broke down the internal clock into five parts: clock, cycle, period, timeless, and cryptochrome2. They analyzed that each of the levels fluctuate in response to daylight. In the case of the C. pipiens, researchers aimed to discover if during the time of diapause, these parts of the clock continued to still run. By using adult mosquitoes (each of which were exposed to different times and length of daylight) the team discovered that the mRNA levels, even during winter, were uninterrupted. This proved to the team of researchers that without the clock, the insects would never know when and when not to be in diapause. This proves that the clock serves as a mechanism to help measure the length of day and night. The researchers also made note of the cryptochrome, which after diapause began to hit peaks at night time. Thus proving when the mosquitoes were active the most, which was during daytime.

After attesting the influence circadian clocks have on diapause, the team decided to concentrate on the five components mentioned previously. To better understand each of their particular roles, researchers wanted to know how reduced mRNA levels would affect the adult female mosquitoes in their ability to reproduce. In order to do this, an RNA molecule designed to stop mRNA from its continuous cycle and prohibit transcription of particular parts of the circadian clock, was injected. The researchers then observed how females exposed to short daylight failed to regulate diapause when the mRNA levels of the last three regulators of the circadian clock were reduced. However, when another part of the circadian clock not mentioned previously, pigment dispersing factor, was also turned off, it initiated diapause when in fact they should have been fertile. This further substantiated that components of the circadian clock do play a vital role in diapause.

After completing their experiment, the researchers concluded how the results paint a bigger picture in the world of ecology than initially anticipated. Aside from the reproductive aspects of C. pipiens, these mosquitoes, as mentioned previously, are in fact a major carrier for diseases like: the West Nile virus, St. Louis encephalitis, and filariasis. With new knowledge on the components of the internal clock needed to be inactivated in order to initiate and halt diapause, researchers hope to prohibit the spread of these diseases in order to create a safe ecological environment. 

Citation:

Meuti, M. E., Stone, M., Ikeno, T. and Denlinger, D. L. 2015. Functional circadian clock genes are essential for the overwintering diapause of the Northern house mosquito, Culex pipiens. The Journal of Experimental Biology 218: 412-422.

Call me maybe? Evolutionary purpose of false mating calls in Pavo cristatus peafowls

Date: March 5, 2014

Source: The American Naturalist  

Summary: A recent study conducted by Roslyn Dakin and Robert Montgomerie at the University of Chicago aims to understand the purpose of false mating calls by Pavo cristatus peafowls.

Evolutionary biology denotes signaling as the communication between organisms. Dishonest signaling, then, is the method by which an organism executes a false alarm to others of its species. For many reasons, dishonest signaling could threaten a species, especially if a predator is involved. In this research however, dishonest signaling has been found to be used by Pavo cristatus peacocks quite frequently: a third of all the mating hoots performed by males. Though generally, peafowl hoots are meant for mating or for attracting peahens (attempt hoot), peacocks have been using it even without the presence of the peahens (solo hoots). It is difficult to explain the purpose of a commonly used dishonest signaling, given its threat to species, which is precisely why this research is novel. The research conducted aimed to understand the purpose of the dishonest signaling executed by the peacocks. It hypothesized that the hoot calls represented male mating success, and thus the preferred males (who were able to mate) hoot more frequently than the unpreferred males.

Researchers observed a total of 39 Pavo cristatus peafowl between 2007 and 2010 at four different sites. Each of the males’ matings as well as hoot calls (attempt and solo) was recorded to determine whether or not a correlation existed between male mating success and male hoot calls. Researchers investigated other various factors such as the attractiveness of the male, the effect of the solo hoot call, the effect of only the hoot on peahen (without male behavior suggesting copulation).

The results of the study seem to bolster the hypothesis as total (attempt and solo) hoots of Pavo cristatus peacocks are representative of a male’s reproductive success as the rates of hooting by a male are linked with female visitation of the male and male copulation with the female. However, though not heavily supported, the results of the study also suggest that the benefit males may gain from false mating (solo) calls would be a slight increase in visitation of female peahens. In addition, the researchers also believe that the dishonest signaling of the males might attract female peahens who might otherwise not respond to mating rituals. Thus, the peahens are mating with lower quality males, falling victim to energetic costs. The researchers suggest a possible explanation for the presence of false mating calls despite its pitfalls: the solo hoot call may be a learned trait part of a reward based learning system where the reward is the ability to mate with females. Further research is needed to provide evidence for this theory.

Dakin R. and R. Montgomerie. 2014. Deceptive copulation calls attract female visitors to peacock
            leks.The American Naturalist 183: 558-564. 

Purpose of Post Reproductive Whales

Source: Current Biology

Summary:

In the article titled Ecological Knowledge, Leadership and the Evolution of Menopause in Killer Whales, the major thesis of the research is that post-reproductively aged females are more likely to lead a group. Post reproductive females are those who are unable to further reproduce because they have gone through menopause. The study further describes that these same females are even more likely to lead a movement when the supply of food is low. The last aspect of this study also expresses the hypothesis that male offspring are more likely to follow a post reproductive female rather than a female offspring.

            The article essentially illustrates the correlation between female humans and their ability to reproduce and then go through menopause and killer whales same ability. In the natural habitat it is often assumed that a female organism’s ability to reproduce is what makes them attractive to the opposite sex. So naturally when a female is going through menopause there survival rates decrease because of no selection. Humans and killer whales are two of the only species known that do end up living and average of 30 years after they stop reproducing. The big question is that why do those individuals who are unable to further reproduce, usually end up leading their families and other members of the species. The article highlights a hypothesis that states how post reproductive members are known to have knowledge on how the hardships of the environment and therefore take on the role to protect the others in their group.

            All the data that was collected for this experiment was done over a long term period of time where 751 hours of footage was screened to gather the results. This footage was taken from the coastal waters of British Columbia. 102 individuals were recorded for observation all ranging in age so that the testing group was random. The classification for leaders was that the member that was at the front or head of the group was considered the leader and every other member was considered a follower.

            The results all showed that females were most often known to be the leaders and rarely ever were the men. The hypothesis was proven and post-menopausal whales were almost always the leaders of the groups. When there was fewer salmon available in an area, a post-menopausal whale often was the leader where if there was an abundance of salmon available the leader could be another female or even a male. This further proves that women who were post reproductive usually chose to be leader and in charge of a situation when a crisis was evident. However the last hypothesis of the sex of the followers was disproved simply for the reason that most of the offspring remained close to their mother and therefore there was no correlation on who followed the mother.

            The major discussion on what “use” post reproductive individuals have was answered by this study. They do play a necessary role in assisting their offspring and other members of the species. Their wisdom makes them a better protector in the end and therefore they do promote an aspect of selection.

Brent L., Franks D., Foster A. E., Balcomb K., Cant M., Croft D.,2015. Ecological Knowledge, Leadership and Evolution of Menopause in Killer Whales. Current Biology.

Free-Living Stages of Gastro-Intestinal Nematode Parasites of Ruminants

In an article written by Hannah Rose, Tong Wang, Jan van Dijk, Eric R. Morgan in February 2015, the study of gastrointestinal nematodes was practiced. The basis of this article explores the affects of gastro-intestinal nematode parasites in livestock. The researchers used simulations through historical and predicted data to illustrate how much the prevalence of infections will increase with increased temperatures. The main findings of this article conclude that regions with increased temperatures are more suitable for the growth of nematode parasites such as H. contortus and T. circumcincta. Furthermore, during winter months, the parasite is less likely to thrive due to the low temperatures of the region, decreasing the overall prevalence of the parasites in livestock. Through this, scientists can predict higher occurrences in the presence of nematodes in livestock in the summer and lower occurrences in the winter. This study is very important because it relates to the food we eat from livestock. Through this, with increased numbers of parasites in livestock, the question of how safe ingesting the infected animals for humans is raised. The fact is, our meat may be very questionable because come of it comes from infected livestock. The parasites could very easily be ingested and absorbed into our bodies. The resulting health effects of these gastro-intestinal nematode parasites need to be studied so that we are aware of possible side effects to the cause. Unfortunately, according the article, it can be very difficult to determine the similarities and differences in the behavior of these parasites in human bodies versus that of livestock. The best solution is to find an efficient way of detecting these parasites and avoiding human ingestion. Not only that, the prevention of the spreading of these parasites among livestock is vital to decreasing its prevalence. By taking careful precautions, we can minimize the dangers these gastro-intestinal parasites raise.

CITATION:

Rose, H. and T., Wong 2015 GLOWORM-FL: A simulation model of the effects of climate and climate change on the free-living stages of gastro-intestinal nematode parasites of ruminants. Ecological Modeling: Vol. 297, p232-245

A Shock from the Past: The Evolution of Electric Organs in Weakly Electric Fish

Aditya Uppuluri

Title: A Shock from the Past: The Evolution of Electric Organs in Weakly Electric Fish

Article Title: Genomic Basis for the Convergent Evolution of Electric Organs

Source: Science

Summary: A new study published in Science finds that similar transcriptional factors may explain the evolution of electric organs in different types of fish.

Researchers from Michigan State University, University of Wisconsin, Harvard Medical School, and other institutions find that similar expression of certain transcription factors explains the evolution of electric organs in certain types of fish.

One of the most interesting adaptations seen in nature is the electric organ. The electric organ is an organ that allows fish to produce an electric field that ranges in strength. Electric organs may be used for defense, communication, and perception. Current information suggests that the electric organ evolved in fish six different times. Electric organs are also known as electrocytes. Electrocytes are essentially groups of modified muscle cells. Unlike the muscle cells of other organisms, electricity generating muscle cells do not have a mechanical component; they do not exert a physical force. Electrocytes work by using ion channels to create voltage differences between the inside and outside of the specialized muscle cells. Anatomically, the arrangement of these specialized muscle cells resembles the stacking of batteries in a flashlight. The shape of the electrocyte varies with the species of fish.

The researchers looked at parts of the genomes of five species of electric fish: Electrophorous electricus, Sternopygus macrurus, Eigenmannia virescens, Brienomyrus brachyistius, and Malapterurus electricus. For experimental purposes, the researchers constructed mRNA sequences from the cells of various electric organs and other internal organs such as the kidneys, brain, and heart. Once these sequences were acquired, scientists compared the genes in these sequences to see if any were regulated in a different way. The scientists looked closely at genes that were highly up-regulated or highly down-regulated in the electric organs but not in skeletal and cardiac muscles. The researchers looked at genes responsible for muscle cell differentiation, the presence of structural proteins, voltage-dependent ion channels, and deactivation of the excitation-contraction function of muscles.

When the researchers compared these genes, they found trends in some genes across the electricity generating fish that were studies. Some genes, such as those that deposited collagen in the specialized muscle cell were highly up-regulated the electric fish species even though the species were not closely related. On the other hand, genes associated with the excitation-contraction pathway were highly down regulated in many species of electric fish.

After analyzing the sequences of these five species of electric fish, the researchers concluded that there were common regulator pathways in many types of electric fish. Scientists as far back as Charles Darwin suggested that there must be some sort of convergent evolution that explains the presence of the electric organ in different lineages. This study supports the theory that common networks of gene regulation and expression were selected for during the evolution of the electric organ in fish.

Labels: Electric Organs, Convergent Evolution, Electric Fish, Electrocytes

Citation:

Gallant J. R., L. L. Traeger, J. D. Volkening, H. Moffett, P. Chen, C. D. Novina, G. N. Phillips Jr., R. Anand, G. B. Wells, M. Pinch, R. Guth, G. A Unguez, J. S. Albert, H. H. Zakon, M. P. Samanta, and M. R. Sussman. 2014. Genomic basis for the convergent evolution of electric organs. Science 344:1522-1525.

Current Ecological Conservation Strategies Attempt to Save the Highest Number of Avian Species, but May Fail to Consider the More Evolutionarily Distinct Species

Date: February 5^th , 2015

Source: Yale University

Summary: Current ecological conservation tries to save as many avian species as possible, which is part of their job. However, there was not enough research done to see the effect of saving the more isolated avian species that are more evolutionarily diverse. The research shown in this research paper shows that prioritizing saving avian species based on their ecological uniqueness, rather than attempting to save as many species as possible, is the more effective strategy to preserve total evolutionary information across all avian species.

Post:

When one thinks of the words “Ecological Conservation”, one might think of security officers restraining elephant poachers, or a zoologist examining a giant panda. However, extinction and the struggle to prevent it range across a plethora of species that are not nearly as exotic. Many species of birds are heading towards extinction, and ecologists have limited resources to stem the tide of extinction. A natural debate arises when these factors are taken into consideration: which species and locations should be given conservation priority? The conventional answer to this question is to simply concentrate resources into locations that have the most endangered species, thus saving as many species as possible. A study conducted at Yale university attempts to offer an alternate solution; to concentrate resources on species with the most ecological uniqueness.

Why is every extinction a tragedy? For every species that will never again walk on this Earth, not only is their ecological niche forever lost, but also their evolutionary information. One reason for ecological conservation is that these species may survive to pass on this evolutionary information. No two species have the same evolutionary uniqueness. Some species are relatively isolated on the phylogenic tree, and it is these species that the researchers at Yale University suggest resources are used to preserve.

There are almost ten thousand species of birds on Earth, and there has not been enough time nor resources to study them all, phylogenically and ecologically. However, phylogenetic information about these bird species have been accumulating at a much faster pace than ecological information. This fact was an inspiration for the Yale research group, as this phylogenic information was then cross referenced with that of other bird species. This allowed for the ranking of birds based on their evolutionary uniqueness. They then located the most evolutionary distinct species, and found that they were generally isolated from other avian species. This means that conventional conservation strategies would not protect these species as well, despite their obvious importance to phylogenetic research.

            In conclusion, these researchers recommend that current conservation priorities be reworked, to consider the evolutionary uniqueness of the species to some capacity.

Citation:

Walter Jetz, Gavin H. Thomas, Jeffrey B. Joy, David W. Redding, Klaas Hartmann, and Arne O. Mooer. 2014. Global distribution and conservation of evolutionary distinctness in birds. Current Biology 24, 919–930

Evidence for Geomagnetic Imprinting and Magnetic Navigation in the Natal Homing of Sea Turtles

Summary: A study done by J. Roger Brothers and Kenneth J. Lohmann on loggerhead sea turtles analyzed a 19 year database of nesting sites for the 12 counties along the east coast of Florida to determine if geomagnetic imprinting was used to return to natal beaches.

Natal homing is a pattern of behavior in which animals migrate away from their geographic area of origin and then return to reproduce in the same location where they were hatched. Loggerhead sea turtles are an extreme case of this. They travel long distances from the beaches they were born, on only to return regularly to nest. Not much is known about how this occurs.

One hypothesis is that turtles imprint on the unique geomagnetic signature of the beach they hatched on and use it to come back. Earth’s magnetic field changes over time the period of time the turtles are away so geomagnetic imprinting should cause turtles to change their nesting locations as magnetic signatures drift slightly causing either longer or shorter nesting spaces along the coastline. 

A convergence index was created to quantify the degree of movement within each county. Analysis of the relationship between each convergence index and nesting densities from the 19 year data base confirmed the predictions of geomagnetic imprinting. The highest convergence indices were associated with the largest nesting densities. Divergence was also associated with low nesting densities. This was true for all 12 counties. 

A similar study done with salmon showed the destination was the same regardless of route, whereas this study shows a change in endpoint due to change in magnetic fields.

These findings confirm and provide strongest evidence to date that sea turtles imprint on the geomagnetic signature of their natal beaches and use it return. The results also confirm the findings of geomagnetic imprinting in salmon and suggest that it is used in natal homing for other animals. 

Citation: Brothers. J.R., Lohmann K.J., 2015. Evidence for Geomagnetic Imprinting and Magnetic Navigation in the Natal Homing of Sea Turtles, Current Biology, Vol. 25. pg 392-396

Freezing and Switching Environments: Testing Local Adaptation of Microbes in Water to Variation in Time and Space

Date Published:  November 20, 2014

Source: Evolution: International Journal of Evolution

Summary:  After freezing isolated microbes of several genera at different times and placing them in each other’s environments, no significant pattern of growth of the microbes depending on chemical balances in the water was detected while bacteria grew slower in their home environments after being frozen for longer periods of time. 

The purpose of the study is to see if organisms are more fit in their native environments due to local adaptations, or similar but foreign environments with slight changes in the biotic and abiotic factors.  This is interesting because one would expect this to be true since natural selection causes populations of organisms to be specifically adapted to their environment.  

In this study, water from 6 different lakes and ponds in Canada was collected.  The aquatic microbes present in the water were isolated, cultured, and frozen.  The chemical balance in each of the water samples (including several elements such as sodium, calcium, magnesium, and potassium) collected was recorded and the water was filtered and frozen as well. Since the microbes and water chemistry was preserved at the time, the thawing of them later on is like having them travel forward in time. 

After, the bacteria that had been isolated was put in each of the different water samples from the different lakes.  
The results showed that bacteria grew more slowly in their native water than in foreign water. Also, results showed that older samples of bacteria grew slower than newer samples.  The water chemistry also did not affect the pattern of growth of the bacteria.  
These results are quite surprising since they are almost opposite of the expected results (it was expected that bacteria would grow faster in their  native environments due to local adaptations).  However, the bacteria were still adapted better to some of the of the 6 environments relative to the others probably due to ideal chemical conditions, although results were inconsistent. 

Citation: Fox, J. W. and Harder, L. D. (2015), Using a “time machine” to test for local adaptation of aquatic microbes to temporal and spatial environmental variation. Evolution, 69: 136–145. doi:10.1111/evo.12543

Adaptations of Aegean Wall Lizards to the Trade-Off Between Natural and Sexual Selection

Date of Publication: July 28th, 2014

Source: Behavioral Ecology

Summary: A study was conducted to investigate whether or not the coloration of Aegean wall lizards has adapted to accommodate the trade-off that exists between highly conspicuous sexual signals and detection avoidance by predators.

________________________________________________________________________________________________________

There currently exists a potentially threatening trade-off between natural and sexual selection in animals. Many animals use sexual signals to attract mates and ward off competition, but all animals are in need of camouflage from predators. This study by Marshall and Stevens of the University of Cambridge's Department of Zoology examines how animals -- in particular, the Aegean wall lizard -- have adapted for this trade-off. Research has shown that conspicuous sexual signals are located on the surfaces of the animals that are in view of their potential mates and rivals (conspecifics), while out of view of predators; at the same time, camouflage is found heavily on the surfaces of animals that are more exposed to their predators' sights. This phenomenon is known as "signal partitioning". The authors of this journal article hypothesized that Aegean wall lizards exemplify signal partitioning; specifically, sexually competing males would be more conspicuous than females to both potential mates/rivals and predators, with camouflaged backs and brightly colored sides, while females would be camouflaged entirely (known as sexual dichromatism).

To test their hypotheses, Marshall and Stevens measured the conspicuousness of 83 wall lizards from three different islands as compared to their natural backgrounds using digital imaging of three regions of the lizards' bodies: ventrolateral flanks, upper backs, and lower backs (see left). They then tested for differences in the perceptions of avian predators and conspecifics of the lizards' coloration and conspicuousness. This was done by converting the pictures of the lizards that were taken on-site into images that would be seen if the camera was actually an avian predator and if the camera was a conspecific. To determine how well lizards blended into their environment/how conspicuous they were from the points of view of an avian predator and a conspecific, the researchers quantified the contrasts between the examined body parts of the photographed lizards and their background environment.

There were several notable results of the performed experiment. For one, the two parts of the lizards' bodies (the part visible to avian predators and the part visible to conspecifics) were distinct in coloration. Moreover, the coloration of the ventrolateral flanks was more distinct from the lizards' backgrounds than the coloration of the upper and lower backs, which supported the initial part of the researcher's hypothesis. In particular, Marshall and Stevens found that males were more conspicuous in coloration on the upper back and flanks, but not on the lower back, suggesting that the flanks and upper back are sexually dichromatic signals in wall lizards. In further support of their hypothesis, the researchers also found that females were inconspicuous throughout all three observed regions of the body, while males had significantly more conspicuous ventrolateral flanks than upper and lower backs.

In conclusion, Marshall and Stevens found much support for their hypothesis concerning the adaptation of Aegean wall lizards to the trade-off between natural and sexual selection. Their findings can be generalized to many animals, in which this signal partitioning adaptation exists, pinpointing one of the great phenomena of evolutionary history.

________________________________________________________________________________________________________

Citation:

Marshall, K.L.A. and Stevens, M. 2014. Wall lizards display conspicuous signals to conspecifics and reduce detection by avian predators. Behavioral Ecology 25(6), 1325–1337

Competing Natural and Sexual Selection: Variation in the Visual Signals of Wall Lizards

Date published: July 28, 2014

Source: Behavioral Ecology

Summary: A study suggests that coloration and conspicuousness of wall lizards evolved under conflicting demands of natural and sexual selection.

            A study suggests that coloration and conspicuousness of wall lizards evolved under conflicting demands of natural and sexual selection, according to a study published in 2014 by Kate Marshall and Martin Stevens from the University of Cambridge in the journal Behavioral Ecology.

            Three populations of Aegean wall lizards were studied from the islands of Skopelos, Syros, and Foelgandros. The authors investigated four main points: whether the lizards were more conspicuous to conspecifics (members of the same species) than to predators, if males were more conspicuous than females as a result of sexual competition, if there was variation in visual signals between different parts of the body, and whether the conspicuousness of the lizards differed among the three populations. Lizards must be noticeable enough to attract potential mates but they must also remain somewhat camouflaged to avoid detection by predators, resulting in conflicting natural and sexual selection.

            The results showed that lizards were more noticeable to conspecifics than to avian predators across all body regions in all three populations. Avian predators can only perceive relatively high wavelengths of UV light while lizards can perceive a much higher range. The increased conspicuousness to conspecifics was caused in part by the use of short UV wavelengths to remain noticeable to potential mates yet avoid detection by predators.

            In the Skopelos population, males exhibited increased conspicuousness over females, but in the Syros population, both males and females displayed higher conspicuousness of certain body regions. The Syros population has a higher population density, which can lead to increased sexual competition, even for females, resulting in the need for both males and females to attract mates. This is indicative of evolution because the conspicuousness varied among populations to best suit the needs of the lizards.

            It was also shown that there was variation in conspicuousness between body parts of the lizards. In the Skopelos and Syros populations, the flanks of the lizards were more conspicuous than the backs. Avian predators view the lizards from above, so their backs were more camouflaged, and because potential mates view the lizards from the side on the ground, the sides of the lizards were more noticeable.

             The Foelgandros population of lizards did not exhibit the significant differences in conspicuousness between body parts that was found in the other two populations. This is likely because the Foelgandros island lacks a number of the avian predators that are on the other islands, so the lizards have a lower risk of detection and therefore less of a need for camouflaged backs.

            The findings of the study indicate that the coloration of the lizards has evolved to make the lizards better suited to their environment. The competing demands of natural selection, which would make the lizards less noticeable to their predators, and sexual selection, which would result in lizards being more conspicuous to potential mates, led to different conspicuousness between certain body regions and differences between males and females. These differences are indicative of evolution.

Journal Reference:

Marshall, K.L.A, and Stevens, M. 2014. Wall lizards display conspicuous signals to conspecifics and reduce detection by avian predators. Behavioral Ecology 25: 1325-1337.

How did the SWS2 Gene Evolve?

Date Accepted: November 19,2014

Source: Wiley Online Library

Institutions Involved: Department of Ecology & Evolution, University of Chicago, Departments of Ecology & Evolutionary Biology, Cell & Systems Biology, University of Toronto, Centre for the Analysis of Genome Evolution & Function University of Toronto,

Summary: Researchers try and find out if color perception in birds had an influence on the evolution of a gene that controls feather color.

Did you ever wonder why some birds have bright feathers while others do not? The researchers from the University of Chicago and the University of Toronto had a similar question. Natasha Bloch, James Morrow, Belinda Change, and Trevor Price wondered, "Why did the Old World warblers have fewer pigmented feathers in comparison to the New World warblers?" So, they decided to conduct an experiment to find out. This particular experiment happens to be interesting because the researchers attempt to find out how the SWS2 gene (which codes for pigment) evolved.

This happens to be the cladogram from the paper. Here, you can see what is referred to as the Old World Warblers and what is referred to as the New World Warblers.

 For this experiment the researchers had three hypotheses. Their null hypothesis stated that the SWS2 gene remained unchanged during the course of evolution. The other two hypotheses each describe different ideas of how the SWS2 gene could have evolved. The first hypothesis believes that the gene is similar in both the New World and Old World Warblers, but was different in their respective anscestors; it also suggests that this difference in color is due to the environment of each of the birds. The second hypothesis states that the gene shifted as the New World Warblers diverged from Old World warblers, but they passed through another ancestor that occupied a different environment, which then lead to the different color perception and color difference in the feathers of each set of birds. This last hypothesis happened to be the researchers' most favored idea.

The researchers tested their ideas by sequencing the SWS2 gene from both of the warbler clades and also from some outgroups. For the New World warblers, the researchers collected birds that died from building collisions during migration in Chicago. For the Old World warblers, they used RNA samples. Once the researchers had  sequenced all of the SWS2 genes from various birs, they then reconstructed the SWS2 sequence evolution. They also identified all the variants with at least one substitution as candidates for shifts in color perception.They found that despite having 6 differences in the amino acid sequences, the ancestors of both

warbler clades had similar color perception.

In conclusion, they found that the color perception of the ancestors of both the New World warblers and the Old World warblers were the same, so this could not have contributed to the evolution (color variation) in the New World warbler's feathers. The researchers say that when they do figure out what the reason for behind the adaptiation is, they will then be easily able to determine if this evolved trait is due to historical  contingency or not.

Journal Reference: Bloch, N. I., Morrow, J. M., Chang, B. S. W. and Price, T. D. (2015), SWS2 visual pigment evolution as a test of historically contingent patterns of plumage color evolution in warblers. Evolution, 69: 341–356. doi: 10.1111/evo.12572