Warning colouration paved the way for louder, more complex calls in certain species of poisonous frogs
Frogs are well-known for being among the loudest amphibians, but new research indicates that the development of this trait followed another: bright colouration. Scientists have found that the tell-tale colours of some poisonous frog species established them as an unappetizing option for would-be predators before the frogs evolved their elaborate songs. As a result, these initial warning signals allowed different species to diversify their calls over time.
Zoologists at the National Evolutionary Synthesis Centre (NESCent), the University of British Columbia, and other research universities assembled an acoustic database to analyse more than 16,000 calls from 172 species within the poison frog family, Dendrobatidae. The paper, which will appear in the December issue of the Proceedings of the Royal Society B, is now available online.
The study included both frogs that display bright colours and others that rely on camouflage for protection. Each call was examined in terms of pitch and duration, and researchers also factored in the size of the frogs and their visibility to predators. They found that because warning colouration protected them from predators, they were better able to attract a mate with low-pitch, pulsing vocalizations in plain sight than their quieter, darker-hued relatives.
“This allows the frog to have a unique type of call—a noisy call,” said lead author Juan C. Santos, formerly of NESCent and now at the University of British Columbia. “These noisy kinds of calls, in general, are what the females really like.”
Scientists already understood that predators shied away from brightly coloured frogs because of visual cues, but Santos and his colleagues hypothesized that some species evolved to include audio signals, as well. Such a warning system is not unprecedented: Tiger moths emit ultrasonic chirps to communicate their unsavoury taste to bats. Without a similar ability, frogs navigate a precarious dilemma in which they must either risk detection by predators or forgo possible courtship.
Initially the researchers expected that audio warnings pre-dated colouration but the results indicate the opposite. Using molecular data and statistical analyses, they were able to infer a phylogenetic tree and pinpoint which trait came first. Their findings indicate that visual traits established the frogs as poisonous and cleared the way for louder, more elaborate calls.
Species relying on camouflage for defence will not invite attention with boisterous calls, while their protected relatives—including non-poisonous frogs that mimic the appearance of their toxic counterparts— can be loud and more nuanced.
“The type of colour they have is in the range of the noisy ones,” Santos said. “When you’re mimicking somebody that’s already protected, you have some freedom to be found by potential mates.”
These calls require high energy expenditures, but the boon of attracting females without predatory threats makes it a rewarding behaviour males. Less is known about the reasons females are attracted to the noisier males and how they appraise the various calls. Santos explained that if the females are being especially picky, it will drive male diversity by pushing them to create even more complex songs.
“What can the females get from this information? Maybe females— by being very picky— increase male diversity,” Santos said. A more diverse pool of potential mates increases the likelihood that their offspring will have more advantageous genes over time.
This work was supported by the National Science Foundation (DEB: 0949899), the National Evolutionary Synthesis Center (NSF EF-0905606 and EF-0423641), and the University of Texas and the Amphibian Tree of Life project (NSF EF-0334952).
Santos, Juan C. et al. (2014). “Aposematism increases acoustic diversification and speciation in poison frogs” Proceedings of the Royal Society B.http://rspb.royalsocietypublishing.org/content/281/1796/20141761.abstract
The National Evolutionary Synthesis Center (NESCent) is a nonprofit science center dedicated to cross-disciplinary research in evolution. Funded by the National Science Foundation, NESCent is jointly operated by Duke University, The University of North Carolina at Chapel Hill, and North Carolina State University. For more information about research and training opportunities at NESCent, visit http://www.nescent.org.
The breakthrough, published in the journal Nature Materials, could offer an easier way of detecting pathogenic bacteria outside of a clinical setting and could be particularly important for the developing world, where access to more sophisticated laboratory techniques is often limited.
The research was led by Professor Cameron Alexander, Head of the Division of Drug Delivery and Tissue Engineering and EPSRC Leadership Fellow in the University’s School of Pharmacy, building on work by PhD student Peter Magennis. Professor Alexander said: “Essentially, we have hijacked some of the metabolic machinery which bacteria use to control their environment, and used it instead to grow polymers which bind strongly to the specific bacteria that produce them.
“The neat thing about this is that the functionality of the polymers grown on the surface of the bacteria is programmed by the cells so that they can recognise their own ‘kind’. We used fluorescent labels to light up the polymers and were able to capture this labelling using a mobile phone camera, so in principle it could be possible to use these materials as point-of-care diagnostics for pathogenic bacteria.”
The study has shown that the bacteria helped to synthesise polymers on their own surfaces which not only were different from those made by conventional methods, but which retained a form of ‘structural memory’ of that surface. This means in future it should be possible to make specific detection agents or additives for topical anti-infectives that target a number of harmful bacteria all by a common route.
“The initial focus of the research was to explore ways to use synthetic polymers to selectively target and bind the bacteria that cause dental cavities and periodontal diseases in order to facilitate their removal from the oral cavity,” said Dr David Churchley, Principal Scientist, Oral Health Category Research and Development, GSK Consumer Healthcare. “As we continued our work, we saw that our research had broader implications and potential for a wider range of uses.”
Rapidly identifying harmful bacteria at the heart of a serious medical or dental condition can be a difficult and costly task. The group’s findings may even lead to new ways of treating bacterial infections. “These types of polymers may be designed to contain antibacterial functionalities so that they specifically bind to and kill bacterial pathogens,” said Dr Klaus Winzer, a microbiologist at The University of Nottingham involved in the study. The selective binding of specific bacterial species and/or strains in current practice requires expensive ‘cold-chain’ reagents such as antibodies which often preclude using these processes outside of a hospital setting or in developing nations.
The new approach, termed ‘bacterial-instructed synthesis’, has the potential for use in the developing world, in the field or in less specialised laboratory settings.
Dr David Bradshaw, Principal Scientist, Oral Health Category Research and Development, GSK Consumer Healthcare, said: “The ingredients used to form the polymers are all easy to obtain, inexpensive and widely available. With the simplicity and accessibility of the chemistry, a number of diagnostic and other applications may be possible.”
Likely related to our ancestors, ‘Plexus ricei’ was much like a tapeworm or modern flatworm, say UC Riverside researchers
Scientists at the University of California, Riverside have discovered a fossil of a newly discovered organism from the “Ediacara Biota” — a group of organisms that occurred in the Ediacaran period of geologic time.
Named Plexus ricei and resembling a curving tube, the organism resided on the Ediacaran seafloor. Plexus riceiindividuals ranged in size from 5 to 80 centimeters long and 5 to 20 millimeters wide. Along with the rest of the Ediacara Biota, it evolved around 575 million years ago and disappeared from the fossil record around 540 million years ago, just around the time the Cambrian Explosion of evolutionary history was getting under way.
“Plexus was unlike any other fossil that we know from the Precambrian,” said Mary L. Droser, a professor of paleontology, whose lab led the research. “It was bilaterally symmetrical at a time when bilaterians—all animals other than corals and sponges—were just appearing on this planet. It appears to have been very long and flat, much like a tapeworm or modern flatworm.”
Study results appeared online last month in the Journal of Paleontology.
“Ediacaran fossils are extremely perplexing: they don’t look like any animal that is alive today, and their interrelationships are very poorly understood,” said Lucas V. Joel, a former graduate student at UC Riverside and the first author of the research paper. Joel worked in Droser’s lab until June 2013.
He explained that during the Ediacaran there was no life on land. All life that we know about for the period was still in the oceans.
“Further, there was a complete lack of any bioturbation in the oceans at that time, meaning there were few marine organisms churning up marine sediments while looking for food,” he said. “Then, starting in the Cambrian period, organisms began churning up and mixing the sediment.”
According to the researchers, the lack of bioturbators during the Ediacaran allowed thick films of (probably) photosynthetic algal mats to accumulate on ocean floors—a very rare environment in the oceans today. Such an environment paved the way for many mat-related lifestyles to evolve, which become virtually absent in the post-Ediacaran world.
“The lack of bioturbation also created a very unique fossil preservational regime,” Joel said. “When an organism died and was buried, it formed a mold of its body in the overlying sediment. As the organism decayed, sediment from beneath moved in to form a cast of the mold the organism had made in the sediment above. What this means is that the fossils we see in the field are not the exact fossils of the original organism, but instead molds and casts of its body.”
Paleontologists have reported that much of the Ediacara Biota was comprised of tubular organisms. The question that Droser and Joel addressed was: Is Plexus ricei a tubular organism or is it an organism that wormed its way through the sand, leaving a trail behind it?
“In the Ediacaran we really need to know the difference between the fossils of actual tubular organisms and trace fossils because if the fossil we are looking at is a trace fossil, then that has huge implications for the earliest origins of bilaterian animals—organisms with bilateral symmetry up and down their midlines and that can move independently of environment forces,” Joel said. “Being able to tell the difference between a tubular organism and a trace fossil has implications for the earliest origins of bilaterian organism, which are the only kinds of creatures that could have constructed a tubular trace fossil. Plexus is not a trace fossil. What our research shows is that the structure we see looks very much like a trace fossil, but is in fact a new Ediacaran tubular organism, Plexus ricei.”
Plexus ricei was so named for plexus, meaning braided in Latin, a reference to the organism’s morphology, and ricei for Rice, the last name of the South Australian Museum’s Dennis Rice, one of the field assistants who helped excavate numerous specimens of the fossil.
“At this time, we don’t know for sure that Plexus ricei was a bilateral but it is likely that it was related to our ancestors,” Droser said.
Most detailed assessment of bonobo across range conducted by University of Georgia, University of Maryland, WCS, and other conservation groups.
The most detailed range-wide assessment of the bonobo (formerly known as the pygmy chimpanzee) ever conducted has revealed that this poorly known and endangered great ape is quickly losing space in a world with growing human populations. The loss of usable habitat is attributed to both forest fragmentation and poaching, according to a new study by University of Georgia, University of Maryland, the Wildlife Conservation Society, ICCN (Congolese Wildlife Authority), African Wildlife Foundation, Zoological Society of Milwaukee, World Wildlife Fund, Max Planck Institute, Lukuru Foundation, University of Stirling, Kyoto University, and other groups.
Using data from nest counts and remote sensing imagery, the research team found that the bonobo— one of humankind’s closest living relatives —avoids areas of high human activity and forest fragmentation. As little as 28 percent of the bonobo’s range remains suitable, according to the model developed by the researchers in the study, which now appears in the December edition of Biodiversity and Conservation.
“This assessment is a major step towards addressing the substantial information gap regarding the conservation status of bonobos across their entire range,” said lead author Dr. Jena R. Hickey of Cornell University and the University of Georgia. “The results of the study demonstrate that human activities reduce the amount of effective bonobo habitat and will help us identify where to propose future protected areas for this great ape.”
“For bonobos to survive over the next 100 years or longer, it is extremely important that we understand the extent of their range, their distribution, and drivers of that distribution so that conservation actions can be targeted in the most effective way and achieve the desired results,” said Ashley Vosper of the Wildlife Conservation Society. “Bonobos are probably the least understood great ape in Africa, so this paper is pivotal in increasing our knowledge and understanding of this beautiful and charismatic animal.”
The bonobo is smaller in size and more slender in build than the common chimpanzee. The great ape’s social structure is complex and matriarchal. Unlike the common chimpanzee, bonobos establish social bonds and diffuse tension or aggression with sexual behaviors.
The entire range of the bonobo lies within the lowland forests of the Democratic Republic of Congo, the largest country in sub-Saharan Africa and currently beset with warfare and insecurity. The research team created a predictive model using available field data to define bonobo habitat and then interpolated to areas lacking data. Specifically, the team compiled data on bonobo nest locations collected by numerous organizations between the years 2003-2010. This produced 2364 “nest blocks,” with a block defined as a 1-hectare area occupied by at least one bonobo nest.
The group then tested a number of factors that addressed both ecological conditions (describing forests, soils, climate, and hydrology) and human impacts (distance from roads, agriculture, forest loss, and density of “forest edge”) and produced a spatial model that identified and mapped the most important environmental factors contributing to bonobo occurrence. The researchers found that distance from agricultural areas was the most important predictor of bonobo presence. In addition to the discovery that only 28 percent of the bonobo range is classified as suitable for the great ape, the researchers also found that only 27.5 percent of that suitable bonobo habitat is located in existing protected areas.
“Bonobos that live in closer proximity to human activity and to points of human access are more vulnerable to poaching, one of their main threats,” said Dr. Janet Nackoney, a Research Assistant Professor at University of Maryland and second author of the study. “Our results point to the need for more places where bonobos can be safe from hunters, which is an enormous challenge in the DRC.”
Dr. Nate Nibbelink, Associate Professor at the University of Georgia, added: “The bonobo habitat suitability map resulting from this work allows us to identify areas that are likely to support bonobos but have not yet been surveyed, thereby optimizing future efforts.”
“By examining all available data provided by a team of leading researchers, we can create the kind of broad-scale perspective needed to formulate effective conservation plans and activities for the next decade,” said Dr. Hjalmar S. Kühl of the Max Planck Institute for Evolutionary Anthropology.
“The fact that only a quarter of the bonobo range that is currently suitable for bonobos is located within protected areas is a finding that decision-makers can use to improve management of existing protected areas, and expand the country’s parks and reserves in order to save vital habitat for this great ape,” said Innocent Liengola, WCS’s Project Director for the Bonobo Conservation Project and co-author on the study.
“The future of the bonobo will depend on the close collaboration of many partners working towards the conservation of this iconic ape,” said Dr. Liz Williamson of the IUCN/SSC Primate Specialist Group and coordinator of the action planning process which instigated the bonobo data compilation for this study. In 2012, the International Union for Conservation and Nature (IUCN) and the Congolese Wildlife Authority (ICCN) published a report titled Bonobo (Pan paniscus): Conservation Strategy 2012-2022.
The authors of the study are: Jena R. Hickey of Cornell University; Janet Nackoney of the University of Maryland; Nathan P. Nibbelink of the University of Georgia; Stephen Blake of the Max Planck Institute of Ornithology; Aime Bonyenge of the Wildlife Conservation Society; Sally Coxe of the Bonobo Conservation Initiative; Jef Dupain of the African Wildlife Foundation Conservation Centre; Maurice Emetshu of the Wildlife Conservation Society; Takeshi Furuichi of the Primate Research Institute, Kyoto University; Falk Grossmann of the Wildlife Conservation Society; Patrick Guislain of the Zoological Society of Milwaukee; John Hart of the Lukuru Foundation; Chie Hashimoto of the Primate Research Institute, Kyoto University; Bernard Ikembelo of the Wildlife Conservation Society; Omari Illambu of the World Wildlife Fund-DR Congo; Bila-Isia Inogwabini of the World Wildlife Fund-DR Congo; Innocent Liengola of the Wildlife Conservation Society; Albert Lotana Lokasola of the Kokolopori Bonobo Nature Reserve; Alain Lushimba of the African Wildlife Foundation Kinshasa Office; Fiona Maisels of the Wildlife Conservation Society and the University of Stirling; Joel Masselink of the Wildlife Conservation Society; Valentin Mbenzo of the Congo Basin Ecosystems Conservation Support Program (PACEBCo), DR Congo; Norbert Mbangia Mulavwa of the Center of Research in Ecology and Forestry (CREF), Ministry of Education and Scientific Research, DR Congo; Pascal Naky of the Wildlife Conservation Society; Nicolas Mwanza Ndunda of the Center of Research in Ecology and Forestry (CREF), Ministry of Education and Scientific Research, DR Congo; Pele Nkumu of the Wildlife Conservation Society; Gay Edwards Reinartz of the Zoological Society of Milwaukee; Robert Rose of the Wildlife Conservation Society; Tetsuya Sakamaki of the Primate Research Institute, Kyoto University; Samantha Strindberg of the Wildlife Conservation Society; Hiroyuki Takemoto of the Primate Research Institute, Kyoto University; Ashley Vosper of the Wildlife Conservation Society; and Hjalmar S. Kühl of the Max Planck Institute for Evolutionary Anthropology.
This study was made possible by the generosity of many supporters.
Why do the faces of some primates contain so many different colors — black, blue, red, orange and white — that are mixed in all kinds of combinations and often striking patterns while other primate faces are quite plain?
UCLA biologists reported last year on the evolution of 129 primate faces in species from Central and South America. This research team now reports on the faces of 139 Old World African and Asian primate species that have been diversifying over some 25 million years.
With these Old World monkeys and apes, the species that are more social have more complex facial patterns, the biologists found. Species that have smaller group sizes tend to have simpler faces with fewer colors, perhaps because the presence of more color patches in the face results in greater potential for facial variation across individuals within species. This variation could aid in identification, which may be a more difficult task in larger groups.
Species that live in the same habitat with other closely related species tend to have more complex facial patterns, suggesting that complex faces may also aid in species recognition, the life scientists found.
“Humans are crazy for Facebook, but our research suggests that primates have been relying on the face to tell friends from competitors for the last 50 million years and that social pressures have guided the evolution of the enormous diversity of faces we see across the group today,” said Michael Alfaro, an associate professor of ecology and evolutionary biology in the UCLA College of Letters and Science and senior author of the study.
“Faces are really important to how monkeys and apes can tell one another apart,” he said. “We think the color patterns have to do both with the importance of telling individuals of your own species apart from closely related species and for social communication among members of the same species.”
Most Old World monkeys and apes are social, and some species, like the mandrills, can live in groups with up to 800 members, said co-author Jessica Lynch Alfaro, an adjunct assistant professor in the UCLA Department of Anthropology and UCLA’s Institute for Society and Genetics. At the other extreme are solitary species, like the orangutans. In most orangutan populations, adult males travel and sleep alone, and females are accompanied only by their young, she said. Some primates, like chimpanzees, have “fission–fusion societies,” where they break up into small sub-groups and come together occasionally in very large communities. Others, like the hamadryas baboons, have tiered societies with harems, clans, bands and troops, she said.
“Our research suggests increasing group size puts more pressure on the evolution of coloration across different sub-regions of the face,” Michael Alfaro said.
This allows members of a species to have “more communication avenues, a greater repertoire of facial vocabulary, which is advantageous if you’re interacting with many members of your species,” he said.
The research, federally funded by the National Science Foundation and supported through a postdoctoral fellowship from the UCLA Institute for Society and Genetics, was published Nov. 11 in the journal Nature Communications.
Lead study author Sharlene Santana used photographs of primate faces for her analysis and devised a new method to quantify the complex patterns of primate faces. She divided each face into several regions; classified the color of each part of the face, including the hair and skin; and assigned a score based on the total number of different colors across the facial regions. This numerical score is called the “facial complexity” score. The life scientists then studied how the complexity scores of primate faces were related to primates’ social systems.
The habitat where species live presents many potential pressures that could have influenced the evolution of facial coloration. To assess how facial colors are related to physical environments, the researchers analyzed environmental variables such as geographic location, canopy density, rainfall and temperature. They also used statistical methods that took into account the evolutionary history and relationships among the primate groups to better understand the evolution of facial diversity and complexity.
While facial complexity was related to social variables, such as group size and the number of closely related species in the same habitat, facial pigmentation was best explained by ecological and spatial factors. Where a species lives is a good predictor of its degree of facial pigmentation — how light or dark the face is.
“Our map shows clearly the geographic trend in Africa of primate faces getting darker nearer to the equator and lighter as we move farther away from the equator,” Lynch Alfaro said. “This is the same trend we see on an intra-species level for human skin pigmentation around the globe.”
Species living in more tropical and more densely forested habitats also tend to have darker, more pigmented faces. But the complexity of facial color patterns is not related to habitat type.
“We found that for African primates, faces tend to be light or dark depending on how open or closed the habitat is and on how much light the habitat receives,” Alfaro said. “We also found that no matter where you live, if your species has a large social group, then your face tends to be more complex. It will tend to be darker and more complex if you’re in a closed habitat in a large social group, and it will tend to be lighter and more complex if you’re in an open habitat with a large social group. Darkness or lightness is explained by geography and habitat type. Facial complexity is better explained by the size of your social group.”
In their research on primates from Central and South America published last year, the scientists were surprised to find a different pattern. For these primates, species that lived in larger groups had more plain facial patterns.
“We expected to find similar trends across all primate radiations — that is, that the faces of highly social species would have more complex patterning,” said Santana, who conducted the research as a postdoctoral fellow with the UCLA Department of Ecology and Evolutionary Biology and UCLA’s Institute for Society and Genetics and who is now an assistant professor at the University of Washington and curator of mammals at the Burke Museum of Natural History and Culture. “We were surprised by the results in our original study on neotropical (Central and South American) primates.”
In the new study, they did find the predicted trends, but they also found differences across primate groups — differences they said they found intriguing. Are primate groups using their faces differently?
“In the present study, great apes had significantly lower facial complexity compared to monkeys,” Lynch Alfaro said. “This may be because apes are using their faces for highly complex facial expressions and these expressions would be obscured by more complex facial color patterns. There may be competing pressures for and against facial pattern complexity in large groups, and different lineages may solve this problem in different ways.”
“Our research shows that being more or less social is a key explanation for the facial diversity that we see,” Alfaro said. “Ecology is also important, such as camouflage and thermal regulation, but our research suggests that faces have evolved along with the diversity of social behaviors in primates, and that is the big cause of facial diversity.”
Alfaro and his colleagues serve as “evolutionary detectives,” asking what factors produced the patterns of species richness and diversity of traits.
“When evolutionary biologists see these striking patterns of richness, we want to understand the underlying causes,” he said.
Human faces were not part of the analysis, although humans also belong to the “clade Catarrhini, which includes Old World monkeys and apes.
Development of cryptic worms provides new insights into molluscan evolution
There are still a lot of unanswered questions about mollusks, e.g. snails, slugs and mussels. The research group of Andreas Wanninger, Head of the Department of Integrative Zoology of the University of Vienna, took a detailed look at the development of cryptic worms. The larvae of the “wirenia argentea” hold a much more complex muscular architecture than their adults — they remodel during their metamorphosis. That’s a clue that the ancestors had a highly complex muscular body plan. Their findings are published in the current issue of the scientific journal “Current Biology“.
With over 200.000 species described, the Mollusca — soft-bodies animals that, among others, include snails, slugs, mussels, and cephalopods — constitutes one of the most species-rich animal phyla. What makes them particularly interesting for evolutionary studies, however, is not the sheer number of their representatives, but rather their vast variety of body morphologies they exhibit. Ever since they have been unambiguously assigned to the phylum, a group of worm-like, shell-less mollusks whose body is entirely covered by spicules — the Aplacophora (“non-shell-bearers”, usually small animals in the mm-range that inhabit the seafloors from a few meters to abyssal depths) has been hotly debated as being the group of today’s living mollusks that most closely resembles the last common ancestor to all mollusks.
However, new studies on the development of a typical aplacophoran (Wirenia argentea, a species that was collected in 200 m depth off the coast of Bergen, Norway) tell a different story. Although their adult, worm-like body appears rather simple (hence the traditional assumption that they may constitute a basal molluscan group), their small, 0.1 to 0.3mm long larvae undergo a stage in which they show an extremely complex muscular architecture which is largely lost and remodeled during metamorphosis to become the simple muscular arrangement of the adult animal. The entire secret these animals hold only unravels if one takes a detailed look at the morphology of these tiny animals. In doing so, Andreas Wanninger, Head of the Department of Integrative Zoology of the University of Vienna, and colleagues found that the musculature of Wirenia larvae in detail resembles that of a quite different-looking mollusk, the so-called polyplacophorans or chitons (flat animals in the cm-range that bear 8 shell plates on their back). In contrast to the former, however, chitons do retain much of the larval muscles as adults. While it has been suspected for a long time that aplacophorans and chitons are closely related, it has often been argued that the aplacophoran morphology is closer to the ancestral molluscan condition than the polyplacophoran one. The current data paint a different picture: the fact that the highly complex larval muscular bodyplan is so similar in both groups but is only carried over into the adult stage in one of them — the chitons — strongly suggests that the common ancestor of both groups was of similar complexity; thereby implying that the worm-like groups lost these complex traits and became secondarily simplified over evolutionary time.
Interestingly, findings from the fossil record support this new developmental evidence. A recently described species from the Silurian — Kulindroplax perissokosmos — obviously had a mix of aplacophoran and polyplacophoran characters: while being long, slender, cylindrical in diameter, and covered by spicules — closely reminding us of today’s aplacophorans — it had seven shells on its back. Although, at an age of 425 myr, too young to be considered the long-sought ancestor of polyplacophorans, aplacophorans and maybe even all mollusks (the origin of the phylum is known to date back to at least the Cambrian Explosion some 540 myr ago), this relative of the distant past proves that evolution has widely played with the combination of the various morphological character sets in individual molluscan groups. Taking together the data currently available, a coherent scenario emerges that strongly suggests that today’s simple, wormy mollusks evolved from an ancestor that had a much more complex musculature (and probably overall internal anatomy) and was covered with protective shell plates.
Researchers find how plants respond to the changing environment in geological time
Understanding the impact of environmental change on plant traits is an important issue in evolutionary biology. As the only direct evidence of past life, fossils provide important information on the interactions between plants and environmental change. After ten years’ survey, Professor Zhou Zhekun’s group from Kunming Institute of Botany has discovered more than ten well preserved Neogene plant fossil sites in southwestern China which are important to understand past climate and response of plants to the changing climate in this region. Their recent work, entitled “Evolution of stomatal and trichome density of the Quercus delavayi complex since the late Miocene”, was published in CHINESE SCIENCE BULLETIN.2013, Vol 58(21).
Comparing closely related fossils from different geological periods is an efficient method to understand how plants respond to climatic change across a large scale. However, few studies have been carried out due to lack of a continuous fossil record. In their recent study, Prof. Zhou’s group investigated detailed micro-morphology of a dominant element in Neogene fossil sites, Quercus delavayi complex (one oak species) to answer this question.
Their results show that Quercus delavayi complex from different periods share similar leaf morphology, but differ with respect to trichome and stomatal densities. The stomatal density of the Q. delavayi complex was the highest during the late Miocene, declined in the late Pliocene, and then increased during the present epoch. These values show an inverse relationship with atmospheric CO2 concentrations. Since the late Miocene, a gradual reduction in trichome base density has occurred in this complex. This trend is the opposite of that of precipitation, indicating that increased trichome density is not an adaptation to dry environments. These results are important to understand the relationship between plant evolution and climatic change which are important to predict the fate of current biodiversity in a changing environment.
This research project was partially supported by a grant from the National Natural Science Foundation of China and a 973 grant from Department of Science and Technology of China. Knowledge of the past is crucial to understand the future. The researchers suggest the old subject ‘Paleontology’ can reveal long term evolution in the past which is hardly seen in ‘Neontology’ should receive more attention.
In this article, we look at five simple examples which support the Theory of Evolution.
The universal genetic code
All cells on Earth, from our white blood cells, to simple bacteria, to cells in the leaves of trees, are capable of reading any piece of DNA from any life form on Earth. This is very strong evidence for a common ancestor from which all life descended.
The fossil record
The fossil record shows that the simplest fossils will be found in the oldest rocks, and it can also show a smooth and gradual transition from one form of life to another.
Please watch this video for an excellent demonstration of fossils transitioning from simple life to complex vertebrates.
Human beings have approximately 96% of genes in common with chimpanzees, about 90% of genes in common with cats (source), 80% with cows (source), 75% with mice (source), and so on. This does not prove that we evolved from chimpanzees or cats, though, only that we shared a common ancestor in the past. And the amount of difference between our genomes corresponds to how long ago our genetic lines diverged.
Common traits in embryos
Humans, dogs, snakes, fish, monkeys, eels (and many more life forms) are all considered “chordates” because we belong to the phylum Chordata. One of the features of this phylum is that, as embryos, all these life forms have gill slits, tails, and specific anatomical structures involving the spine. For humans (and other non-fish) the gill slits reform into the bones of the ear and jaw at a later stage in development. But, initially, all chordate embryos strongly resemble each other.
In fact, pig embryos are often dissected in biology classes because of how similar they look to human embryos. These common characteristics could only be possible if all members of the phylum Chordata descended from a common ancestor.
Bacterial resistance to antibiotics
Bacteria colonies can only build up a resistance to antibiotics through evolution. It is important to note that in every colony of bacteria, there are a tiny few individuals which are naturally resistant to certain antibiotics. This is because of the random nature of mutations.
When an antibiotic is applied, the initial innoculation will kill most bacteria, leaving behind only those few cells which happen to have the mutations necessary to resist the antibiotics. In subsequent generations, the resistant bacteria reproduce, forming a new colony where every member is resistant to the antibiotic. This is natural selection in action. The antibiotic is “selecting” for organisms which are resistant, and killing any that are not.
Researchers discover rare ‘old world’ ape cranium fossil in China
A team of scientists from Penn State, The Cleveland Museum of Natural History, Arizona State University, Peabody Museum of Archaeology and Ethnology at Harvard University, and the Yunnan Cultural Relics and Archaeology Institute has announced a new cranium of a fossil ape from Shuitangba, a Miocene site in Yunnan Province, China.
The new juvenile cranium of the fossil ape Lufengpithecus, recently described online in the Chinese Science Bulletin, is a significant discovery because juvenile crania of apes and hominins are extremely rare in the fossil record, especially those of infants and young juveniles. The new cranium is only the second relatively complete cranium of a young juvenile in the entire Miocene (23-5 million years ago) record of fossil apes throughout the Old World, and both were discovered from the late Miocene of Yunnan Province. The new cranium is also noteworthy for its age. Shuitangba, the site from which it was recovered, at just over 6 million years, dates to near the end of the Miocene, a time when apes had become extinct in most of Eurasia. Shuitangba has also produced remains of the fossil monkey, Mesopithecus, which represents the earliest occurrence of monkeys in East Asia.
“The fossils recovered from Shuitangba constitute one of the most important collections of late Miocene fossils brought to light in recent decades because they represent a snapshot from a critical transitional period in earth history,” said Dr. Nina Jablonski, co-author and Distinguished Professor of Anthropology at Penn State. “The ape featured in the current paper typifies animals from the lush tropical forests that blanketed much of the world’s subtropical and tropical latitudes during the Miocene epoch, while the monkey and some of the smaller mammals exemplify animals from the more seasonal environments of recent times.”
Jay Kelley, Institute of Human Origins and School of Human Evolution and Social Change at Arizona State University, said, “The preservation of the new cranium is excellent, with only minimal post-depositional distortion. This is important because all previously discovered adult crania of the species to which it is assigned, Lufengpithecus lufengensis, were badly crushed and distorted during the fossilization process. In living ape species, cranial anatomy in individuals at the same stage of development as the new fossil cranium already show a close resemblance to those of adults.
“Therefore, the new cranium, despite being from a juvenile, gives researchers the best look at the cranial anatomy of Lufengpithecus lufengensis,” he noted. “Partly because of where and when Lufengpithecus lived, it is considered by most to be in the lineage of the extant orangutan, now confined to Southeast Asia but known from the late Pleistocene of southern China as well. “
The team notes that however, the new cranium shows little resemblance to those of living orangutans, and in particular, shows none of what are considered to be key diagnostic features of orangutan crania.Lufengpithecus therefore appears to represent a late surviving lineage of Eurasian apes, but with no certain affinities yet clear. The survival of this lineage is not entirely surprising since southern China was less affected by the climatic deterioration during the later Miocene that resulted in the extinction of many ape species throughout the rest of Eurasia. The researchers are hopeful that renewed excavations will produce the remains of adult individuals, which will allow them to better assess both the relationships among members of this lineage as well as the relationships of this lineage to other fossil and extant apes.
“In addition to the ape, we have recovered hundreds of specimens of other animals and plants,” said co-author Dr. Denise Su, Curator of Paleobotany and Paleoecology at The Cleveland Museum of Natural History. “We are looking forward to going back to Shuitangba next year to continue fieldwork and, hopefully, find more specimens of not only the ape but other animals and plants that will tell us more about the environment. Given what we have recovered so far, Shuitangba has great potential to help us learn more about the environment in the latest part of the Miocene in southern China and the evolution of the plants and animals found there.”
The team of scientists include: Xue-Ping Ji, Yunnan Institute of Cultural Relics and Archaeology, China; Nina Jablonski, Penn State; Denise Su, Cleveland Museum of Natural History; Cheng Long Deng, State Key Laboratory of Lithospheric Evolution, China; J. Lawrence Flynn, Harvard University; You-Shan You, Zhaotong Institute of Cultural Relics, China; and Jay Kelley, Arizona State University.
The project was supported by the National Science Foundation, Bryn Mawr College, American Association of Physical Anthropologists, the Yunnan National Science Foundation, the Zhaotong government, National Basic Research Program of China, and the National Natural Science Foundation of China.
With new insights into the classical game theory match-up known as the “Prisoner’s Dilemma,” University of Pennsylvania biologists offer a mathematically based explanation for why cooperation and generosity have evolved in nature.
Their work builds upon the seminal findings of economist John Nash, who advanced the field of game theory in the 1950s, as well as those of computational biologist William Press and physicist-mathematician Freeman Dyson, who last year identified a new class of strategies for succeeding in the Prisoner’s Dilemma.
Postdoctoral researcher Alexander J. Stewart and associate professor Joshua B. Plotkin, both of Penn’s Department of Biology in the School of Arts and Sciences, examined the outcome of the Prisoner’s Dilemma as played repeatedly by a large, evolving population of players. While other researchers have previously suggested that cooperative strategies can be successful in such a scenario, Stewart and Plotkin offer mathematical proof that the only strategies that succeed in the long term are generous ones. They report their findings in PNAS the week of Sept. 2.
“Ever since Darwin,” Plotkin said, “biologists have been puzzled about why there is so much apparent cooperation, and even flat-out generosity and altruism, in nature. The literature on game theory has worked to explain why generosity arises. Our paper provides such an explanation for why we see so much generosity in front of us.”
The Prisoner’s Dilemma is a way of studying how individuals choose whether or not to cooperate. In the game, if both players cooperate, they both receive a payoff. If one cooperates and the other does not, the cooperating player receives the smallest possible payoff, and the defecting player the largest. If both players do not cooperate, they receive a payoff, but it is less than what they would gain if both had cooperated. In other words, it pays to cooperate, but it can pay even more to be selfish.
In the Iterated Prisoner’s Dilemma, two players repeatedly face off against one another and can employ different strategies to beat their opponent. In 2012, Press and Dyson “shocked the world of game theory,” Plotkin said, by identifying a group of strategies for playing this version of the game. They called this class of approaches “zero determinant” strategies because the score of one player is related linearly to the other. What’s more, they focused on a subset of zero determinant approaches they deemed to be extortion strategies. If a player employed an extortion strategy against an unwitting opponent, that player could force the opponent into receiving a lower score or payoff.
Stewart and Plotkin became intrigued with this finding, and last year wrote a commentary in PNAS about the Press and Dyson work. They began to explore a different approach to the Prisoner’s Dilemma. Instead of a head-to-head competition, they envisioned a population of players matching up against one another, as might occur in a human or animal society in nature. The most successful players would get to “reproduce” more, passing on their strategies to the next generation of players.
It quickly became clear to the Penn biologists that extortion strategies wouldn’t do well if played within a large, evolving population because an extortion strategy doesn’t succeed if played against itself.
“The fact that there are extortion strategies immediately suggests that, at the other end of the scale, there might also be generous strategies,” Stewart said. “You might think being generous would be a stupid thing to do, and it is if there are only two players in the game, but, if there are many players and they all play generously, they all benefit from each other’s generosity.”
In generous strategies, which are essentially the opposite of extortion strategies, players tend to cooperate with their opponents, but, if they don’t, they suffer more than their opponents do over the long term. “Forgiveness” is also a feature of these strategies. A player who encounters a defector may punish the defector a bit but after a time may cooperate with the defector again.
Stewart noticed the first of these generous approaches among the zero determinant strategies that Press and Dyson had defined. After simulating how some generous strategies would fare in an evolving population, he and Plotkin crafted a mathematical proof showing that, not only can generous strategies succeed in the evolutionary version of the Prisoner’s Dilemma, in fact these are the only approaches that resist defectors over the long term.
“Our paper shows that no selfish strategies will succeed in evolution,” Plotkin said. “The only strategies that are evolutionarily robust are generous ones.”
The discovery, while abstract, helps explain the presence of generosity in nature, an inclination that can sometimes seem counter to the Darwinian notion of survival of the fittest.
“When people act generously they feel it is almost instinctual, and indeed a large literature in evolutionary psychology shows that people derive happiness from being generous,” Plotkin said. “It’s not just in humans. Of course social insects behave this way, but even bacteria and viruses share gene products and behave in ways that can’t be described as anything but generous.”
“We find that in evolution, a population that encourages cooperation does well,” Stewart said. “To maintain cooperation over the long term, it is best to be generous.”
The study received support from the Burroughs Wellcome Fund, David and Lucile Packard Foundation, James S. McDonnell Foundation, Alfred P. Sloan Foundation, Foundational Questions in Evolutionary Biology Fund, U.S. Army Research Office and U.S. Department of the Interior.