Does Urbanization Always Drive Economic Growth? Not Exactly…


We often think of cities as major drivers of economic development and growth. Big cities expand our access to infrastructure like public transit and public education. They allow for more efficient distribution of social services such as government assistance and health care. Cities create large markets for business, and can attract international investment and tourism from around the world. They are hubs of non-agricultural, high-paying professional jobs like banking, law, and engineering. Diversity and face-to-face interactions can lead to new ideas and cross-cultural collaborations. Conventional wisdom holds that cities are good for the economy.

Indeed, the link between a country’s level of urbanization and the size of its gross domestic product (GDP) is well established. The below graph of 2011 data illustrates the strong positive correlation: developed countries with high GDPs have relatively high proportions of their population living in urban areas, and vice versa.

Correlation graphLooking at this graph, it is small wonder, then, that urbanization has become a widely adopted global development strategy. National governments and international development agencies have embarked upon aggressive programs of accelerated urbanization designed to spur economic growth. Simply attract people into the cities, the thinking goes, and then cash in on the forthcoming economic benefits of a largely urban population. Well, it may be more complex than that, according to new research published in PLOS ONE.

Researchers in China examined global economic data on urbanization and per capita GDP levels spanning three decades (1980-2011). During this time, the proportion of the world’s population living in cities grew from just 39% in 1980 to 52% in 2011. And while urbanization and per capita GDP may be strongly correlated, the authors found no correlation between the rates of urbanization and economic growth. In other words, fast urban growth doesn’t always translate into fast GDP growth, as witnessed by the graph below. In stark contrast to the first graph, there is no easily discernible pattern connecting the speed of urbanization and the speed of GDP growth.

Graph with no correlation

The authors also point out that over three decades, many countries—for example, Gabon—had rapidly growing urban populations but low and even negative economic growth (top graph in green below). Conversely, many countries, such as Sri Lanka and Uzbekistan, saw negative rates of urbanization— people leaving cities for rural areas—but still had positive overall economic growth (bottom graph in white). These cases do not support the hypothesis that fast urbanization speeds economic growth.


The authors of the study argue that GDP growth may create conditions that organically drive migration from rural to urban areas, but the assumption that urbanization will necessarily drive strong economic growth may be false. Pointing to the numerous examples of accelerated urbanization without strong economic growth (again, the green graph above), they caution that “urbanization is not an automatic panacea” for economic difficulties. Citing other work, the authors suggest that instead of trying to move people into cities, governments and development agencies should focus on creating a mobile workforce, ensuring broad access to goods and markets, implementing government policies that support commerce, and investing in infrastructure. These efforts could make a bigger difference for short- and medium-term economic growth than arbitrary urbanization targets.

While economic growth is an incredibly complex process and much work remains, this study serves as a good reminder not to confuse causation and correlation: just because two variables are closely related doesn’t necessarily mean that one directly causes the other.

Related Content:

Does Human Migration Affect International Trade? A Complex-Network Perspective

Welcome to The World’s Largest Ghost City: Ordos, China

Citation: Chen M, Zhang H, Liu W, Zhang W (2014) The Global Pattern of Urbanization and Economic Growth: Evidence from the Last Three Decades. PLoS ONE 9(8): e103799. doi:10.1371/journal.pone.0103799

Images: Images are from Figures 4 and 5 of the published paper, and from Chi King via Flickr.

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Meet PLOS at the Society of Vertebrate Paleontology 2014

SVP Blog ImageWe are excited to announce that PLOS will be exhibiting at the Society of Vertebrate Paleontology 2014 Annual Meeting from 5-8th November in Berlin.

This is only the second time that the meeting takes place outside North America, and the first time it will be held in continental Europe. To celebrate our attendance PLOS ONE Section Editor, Dr Andy Farke, has specially curated some articles recently published by PLOS. Featured articles range from a description of the oldest Caseid Synapsid to the discovery of a new Ankylosaurid dinosaur, plus many more themed selections. We’ll be giving away some PLOS memorabilia and USB drives featuring this specially curated content, so do visit us early before supplies run out!

We’ll be on the Exhibit Floor, at Booth #14 where you can meet Jenni Horsley, PLOS Collections Editorial Project Coordinator and Alejandra Clark, PLOS ONE Associate Editor. We look forward to meeting you in Berlin and hearing your thoughts about PLOS, open access, open data, and open science.

Image: Godoy PL et al., 2014 (CC-BY)

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Going PRO – clinical trials must plan to capture patient-reported outcomes

14425819028_5021bbcb74_zPost authored by David Moher

All participants in research are important. What patients in clinical trials tell us about treatments – patient-reported outcomes (PROs) such as quality of life and symptoms – is being used more and more to improve decisions about patient-centered care and health policy, but poor reporting of these outcomes risks research effort being wasted. Today, PLOS ONE publishes two important papers concerning patient-reported outcomes.[1,2] Professor Melanie Calvert at the University of Birmingham and her colleagues across the UK, Canada and Australia found that not enough attention has been devoted to PROs in clinical trial protocols, the blueprints for how a trial is run and reported.

Patient-reported outcomes are now getting the focused attention they deserve. In the United States the Patient-Centered Outcome Research Institute was set up in 2010 to conduct “research that answers patients’ questions”, spending nearly $700 million USD on 360 projects. The Canadian Institutes of Health Research recently established the Strategy for Patient-Oriented Research. However, PROs must be collected rigorously from the beginning to minimise loss of research information. CONSORT, the Consolidated Standards of Reporting Trials, has long been the gold standard for trial reporting. In 2013 the CONSORT-PRO Extension was introduced, promoting the transparent reporting of PRO data from trials. However, this guidance is aimed at the end of the research process and may be too late to make researchers think more about patients earlier on – at the protocol stage. Guidance on preparing trial protocols themselves has been developed – the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) checklist was also published in 2013. However, this does not offer PRO-specific guidance.

In the first paper, Calvert and colleagues review the existing guidance for protocol writers on PROs.[1] They found that guidance was hard to access, lacked consistency and may be challenging to put into practice.  In total they uncovered a confusing mix of 162 recommendations across 54 publications.

In the second paper, Kyte and colleagues studied 75 protocols funded by the UK National Institutes of Health Research’s Health Technology Assessment program in 2012-3.[2] About two-thirds of the protocols complied with reporting SPIRIT items. Most troubling was that two of items about randomization – the unique characteristic of randomized trials – were missing in about a fifth of the protocols. Anything less than 100% is avoidable waste and the funder is not getting value for money. More than a third of the sample selected was from 2012, prior to the introduction of SPIRIT, however the NIHR website’s guidance for prospective protocol developers still only suggests using SPIRIT (in section 4.4). This is in contrast to a stronger endorsement of PROSPERO, a registry for systematic review protocols. Clearly there is an opportunity to more strongly recommend using SPIRIT, incorporating PRO issues at the same time.

These papers point to a clear need for more attention to PROs when developing trial protocols, and Prof. Calvert and colleagues used rigorous evidence-based methods that were explicitly reported in sufficient detail to allow interested readers to replicate them.

One suggestion to improve reporting is the development of a SPIRIT PRO extension. The EQUATOR Network already has a library of more than 200 reporting guidelines, with lots more in development. Reporting guideline developers have worked hard to help authors more completely report their research, but the marketplace is getting full. The SPIRIT-PRO extension would need to be both accessible and acceptable to researchers who wish to incorporate PROs in their trials and we need to ensure we don’t make using guidelines, such as a SPIRIT PRO extension, so complicated that it becomes a barrier to using them. We need to consider how to best ease using reporting guidelines: technology might be helpful here.

Another way to increase the use of SPIRIT and PRO guidance would be to build them into teaching about trials in university graduate programs, such as epidemiology and biostatistics. However this is done, researchers need to improve the reporting of patient-reported outcomes for the sake of both the trial participants and the patients who rely on this evidence to improve their health.

Citations: [1] Calvert M et al. (2014) Patient-Reported Outcome (PRO) Assessment in Clinical Trials: A Systematic Review of Guidance for Trial Protocol Writers. PLOS ONE  9(10): e110216 doi:10.1371/journal.pone.0110216

[2] Kyte D et al. (2014) Systematic evaluation of the patient-reported outcome (PRO) content of clinical trial protocols. PLOS ONE  9(10): e110299. doi:10.1371/journal.pone.0110229

Image: Hands_II – Oleg Afonin

david_moherDavid Moher is a senior scientist in the Clinical Epidemiology Program, Ottawa Hospital Research Institute, and Associate Professor, Department of Epidemiology and Community Medicine, University of Ottawa, where he holds a University Research Chair. He has a special interest in journalology (publication science), including ways to improve the quality of reporting health research. He spearheaded the development of the CONSORT Statement for reporting randomized trials, the PRISMA Statement for reporting systematic reviews and meta-analyses, and has been involved in many other reporting guideline initiatives, including SPIRIT and CONSORT PRO. Dr. Moher is associated with many journals: an editor-in-chief of Systematic Reviews; an editorial board member of several journals, including PLOS Medicine, a member of PLOS ONE’s Human Research Advisory Group, the advisory board for the International Congress on Peer Review and Biomedical Publication, and a member of the EQUATOR Network’s steering group.

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Hey, Excuse Me… Is This Guy Boring You?

pone.0100366 Featured Image

Imagine that you’re sitting on a Cretan beach. The sun’s shining and waves are lapping on shore, when suddenly a set of jaws dripping copious amounts of saliva appear above you like some sort of CGI horror masterpiece, wanting to bore a hole in you big enough to crawl through. While this is hopefully not something you need to worry about, it is in fact a concern for the Albinaria land snails that inhabit the Greek islands. Who are the boorish culprits? No other than small beetle larvae of the genus Drilus (shown above), a land snail predator.

In a study recently published in PLOS ONE, researchers aimed to gain a better understanding of the predator-prey interactions between Drilus beetle larvae and Albinaria land snails. They predicted that land snail species with a greater number of ribs on their shell were better protected from invasion; if correct, this would mean the type of predation may affect shell evolution in this species.

The authors surveyed over 1,000 groups of land snail shell samples from a museum and mapped, by region, the frequency of land snail deaths by beetle larvae. Then, using DNA sequencing, they found that while some species of beetle larvae only prey on Albinaria, others take a more generalist approach and feed on a variety of land snail species.

The authors also found that beetle larvae can kill without ever actually having to bore a hole in the snail’s shell. In fact, of the ~170 Albinaria shells the authors collected that showed evidence of a beetle larvae attack, 60 shells had no holes. The researchers suggest that despite the potential challenges of entering through the main opening, such as encountering the clausilium—essentially a front door that the snail can shut (as drawn above)—boring into the shell is still a more rigorous task.

pone.0100366 Second Image

The scientists’ also directly observed the beetle larvae preying on the land snails, which reinforced that it was not necessary to bore a hole for entry; however, they found that the beetle larvae almost always exited by boring. While there does not seem to be an obvious explanation for why this variation in entry/exit method exists, each choice has its own advantages and disadvantages. The observation period further revealed that the beetle larvae took its time leaving the shell, often living inside it for 22-32 days after each kill before molting and moving on.

Though we still do not have a clear understanding of how these interactions directly impact shell evolution, the authors hope this research provides a basis for future work to build upon. Regardless, I think it’s safe to say that this ‘boring’ research yielded some rather informing results.

Citation: Baalbergen E, Helwerda R, Schelfhorst R, Castillo Cajas RF, van Moorsel CHM, et al. (2014) Predator-Prey Interactions between Shell-Boring Beetle Larvae and Rock-Dwelling Land Snails. PLoS ONE 9(6): e100366. doi:10.1371/journal.pone.0100366

Images: All images are from the article.

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Worms in the Big Apple: Identifying Patterns of Toxocariasis Infection in New York City

For thousands of Americans, roundworm infection may pose a serious threat to their health. Toxocariasis, an illness caused by a parasitic roundworm, can potentially cause chronic health problems, including ocular infections, diminished lung function, and poor cognitive development. It is estimated to be one of the most prevalent neglected infections of poverty (NIP) in the United States, a group of “under the radar” infections that cause major problems for those living in poverty.

Public health officials know that toxocariasis is highly prevalent in urban areas and inner city neighborhoods, but beyond that, this disease isn’t tracked or treated like other illnesses where extensive background research is more accessible. The authors of a paper published in PLOS ONE in June of this year attempted to take a step closer to addressing this issue by looking at how data like ethnicity, education level, or neighborhood size in New York City can provide clues to the likelihood of toxocariasis occurrence.

Figure 1

The researchers in this study used the only source of population-based and location-specific information about toxocariasis that was available: a 1988-1994 National Health and Nutrition Examination Survey (NHANES) that contains a collection of data used to estimate the prevalence of this infection around the United States. By applying these statistics to highly detailed census data from urban areas of New York City, the authors could estimate the probability of toxocariasis in different demographics or neighborhoods. The results of this are shown in the map above.

Figure 2

As this second map indicates (click to enlarge), several different ethnicities in inner cities are at a higher risk for this infection. For instance, African Americans in New York City show a 64% greater risk of infection, and immigrants had a 92% greater chance of infection in comparison to those born in the US. Not only that, New Yorkers’ education levels also correlated with infection: the risk of toxocariasis was about 6% among US-born Latino women with a university education, and up to 57% among immigrant men with less than a high school education. These populations appear to be at particularly high risk for infection, and might be among the first groups surveyed in targeted sampling.

The results of this study are particularly telling for the US’ largest city, which holds almost 8.4 million people in all of its diverse neighborhoods. Wandering the streets of New York at any moment, you might hear one of 800 spoken languages. The dense populations of this city are key to understanding where and why these neglected infections of poverty can develop. More specifically, the colorful areas of these maps can be used to guide testing in inner city neighborhoods.

A few limitations of the study might be that the nationwide (NHANES) survey was conducted 15 years earlier, and it captured far fewer details than the New York City census data. Still, the vivid depictions of these statistics can provide us with much-needed maps for further research and potential surveillance. With more surveillance of this illness, we can gather more data, track, and study this disease. Once we have improved sampling methods, we can better address the public health needs of our urban areas.

Citation: Walsh MG, Haseeb MA (2014) Small-Area Estimation of the Probability of Toxocariasis in New York City Based on Sociodemographic Neighborhood Composition. PLoS ONE 9(6): e99303. doi:10.1371/journal.pone.0099303

Images: All images are from the article.

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Catch the Katydid if You Can


Katydid pic 1

It’s too fast to catch, spears smaller insects with spiny legs, and sings a song that mirrors the syllables of its name, “Ka-ty-did, Ka-ty-didn’t.­ Its music is so catchy, it has even been used as the chorus of popular songs.

Listroscelidinae are a group of insectivorous katydid hunters from South America whose fast and aggressive behavior makes them difficult to capture, let alone identify. According to the authors of a recent PLOS ONE study, these Neotropical katydids have been understudied, partly because we haven’t been able to get our hands on them. However, the authors of this study managed to collect more than 100 specimens from one of the world’s most threatened ecosystems, the Brazilian Atlantic Forest.

They compared these new specimens to existing samples from museums by collecting DNA samples and creating simplified illustrations to document the differences between the physical characteristics in each species. In addition to measuring the phalluses and abdomens, they traced the placement of stridulatory files on their wings, shown in the image below, which katydids rub together to make noise. The different placement of these bands allowed the researchers to distinguish between related species.

After examining the physical characteristics and DNA samples, researchers were able to identify and name eight new species of Neotropical katydids, which have been very difficult to classify and have been re-categorized several times in the last century.

The most distinctive feature of these Neotropical katydids is their spiked legs, which they use to skewer and ensnare insect prey. A close relative of the Listroscelidinae, the Red-eyed Devil, has been documented performing the katydid hunt.

Katydids blogpost

The authors caution that these species may be seriously endangered as they are found only in highly-preserved sections of this threatened forest. Identifying these species has helped reshape how researchers think about them, but there is still much research to be done on this group of Neotropical katydids, as long as researchers can catch up with them!

Citation: Fialho VS, Chamorro-Rengifo J, Lopes-Andrade C, Yotoko KSC (2014) Systematics of Spiny Predatory Katydids (Tettigoniidae: Listroscelidinae) from the Brazilian Atlantic Forest Based on Morphology and Molecular Data. PLoS ONE 9(8): e103758. doi:10.1371/journal.pone.0103758

Images: All images are from the article.

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Detection by Dung: Don’t Eat the Brown Snow


Researchers in Antarctica on a mission to locate penguin colonies found two groups of seabirds, thanks to a little help from satellites, helicopters, and the detection of more “primitive” evidence: penguin poop.

Our favorite tuxedo-clad Emperor penguin is native to Antarctica, but harsh winter conditions and the remoteness of some colonies can make it difficult for biologists to gain a comprehensive population assessment of this “hiding” bird. The first breeding penguin colony was discovered in Antarctica in 1902, and in 1999 thousands of birds were sighted near the Mertz glacier in Antarctica, but for the last century, suspected colonies of Emperor Penguins in the area had yet to be confirmed.

In this recently published PLOS ONE study, the authors used both survey- and satellite-based methods to locate the presence of Emperor penguin colonies on the Mertz glacier, where a previous sighting of thousands of birds had occurred 15 years ago, but a drastic habitat change—the glacier’s “tongue” broke off in February 2010—may have disrupted.


Aerial surveys captured two new potential breeding grounds for colonies, the Eastern and Western (~7,400 breeding pairs total).  Satellite images from a thousand feet in the sky helped the authors detect the Eastern colony by the presence of fecal marks—or in bird specialist speak, “guano”—in the snow.

The red arrow in the image above points out the lovely brown streak of guano strewn across the ice shelf, which indicates the Eastern colony’s previous breeding ground. The authors used this streak as an indication that the Eastern colony was likely close by. Below the guano-streaked, snow-packed shelf, the presence of the Eastern colony was confirmed by researchers trekking across treacherous terrain to visually confirm the presence of the birds.

Unlike the Eastern colony, who mobilized to a fresh home post-breeding, the Western colony seemingly didn’t mind remaining in their breeding muck. This colony was discovered not by satellite but by chance during helicopter flight operations in Antarctica. Although the authors had difficulties finding the Western colony by aerial footage, as pictured in the below image, these social gatherers appeared to differ from the Eastern colony in that they inhabited a large flat surface, and the colony appeared to be much larger.


In the cases of both colonies, aerial surveys appeared to be very effective for locating them. So, until humans evolve warmer winter coats, scientists conducting surveys by foot are still limited by frigid conditions and isolated locations in future South Pole endeavors. To obtain a more accurate picture of total penguin counts, the authors suggest taking multiple aerial images during the breeding season and conducting several-year surveys to confirm numbers in suspected Antarctic penguin colonies. But for now, the game of Hide and Go Poop will continue.

Citation: Ancel A, Cristofari R, Fretwell PT, Trathan PN, Wienecke B, et al. (2014) Emperors in Hiding: When Ice-Breakers and Satellites Complement Each Other in Antarctic Exploration. PLoS ONE 9(6): e100404. doi:10.1371/journal.pone.0100404

Image 1: Emperor Penguins by Lin Padgham

Image 2-3: Figures 1 and 2 from article

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Article-Level Metrics Highlight: Top 10 of the Summer

summerHaving just published our 100,000th article, the staff at PLOS ONE realizes that easily finding research papers among our wide selection is very important to our diverse community. This is one reason we’ve now joined forces with the PLOS article-level metrics (ALMs) team to regularly identify and present a selection of our recently published papers that demonstrate high ALM activity*. This post will be the first in a series that highlights new content for our readers.

From genetics to paleontology and microbiology to ecology, all the papers featured here have drawn the attention of the general public and scientific community over the past four months. This list is just the tip of the iceberg and if you haven’t already perused these papers, we encourage you to explore the work here and join the rich conversations already ongoing surrounding them.

Without further ado, this month’s top papers include the following:

1. Investigating “knockin” and “knockdown” in a human cell line

Using CRISPR/Cas9, a biological gene editing system that has allowed rapid and efficient modification of an organism’s DNA—as well as captured the imagination of biomedical researchers in the last two years—the authors of “CRISPR/Cas9 Allows Efficient and Complete Knock-In of a Destabilization Domain-Tagged Essential Protein in a Human Cell Line, Allowing Rapid Knockdown of Protein Function” were able to add a destabilizing element to “knockdown” an essential gene ( TCOF1) in a human cell line, effectively impairing cell growth and controlling protein levels. This strategy will hopefully allow the authors to investigate this gene further, as it is critical for cell growth and viability and has been associated with Treacher Collins–Franceschetti syndrome.

Published 4/17/2014, Image from the article

2. The shapes of 2.1 billion year-old macroscopic marine biota

The authors of “The 2.1 Ga Old Francevillian Biota: Biogenicity, Taphonomy and Biodiversity” analyzed the shapes and structures of fossilized material from the Paleoproterozoic Era—when the Earth’s surface and atmospheric environment was still in flux—found in the Francevillian black shale rocks in southeastern Gabon in Central Africa. The results suggest a biota fossilized during the formation of sedimentary rocks, likely following the rise and fall of atmospheric oxygen. These 400 biota may represent the oldest known macroscopic organisms.

Published 6/25/2014, Image from the article

3. Musical training may benefit young brains

The authors of “Behavioral and Neural Correlates of Executive Functioning in Musicians and Non-Musicians” put working adult musicians, adults with no musical training, and kids with a couple years of musical training through a series of tasks to measure various cognitive capabilities. They found that the adults and children with musical training showed enhanced performance in working memory and processing speed compared to those without training.

Published 6/17/2014, Image from the article

4. Cheers for the “bugs” in Lambic beers’ (yeast and bacteria)

Traditional Lambic sour beers ferment for one to three years before bottling using wild yeast and bacteria from the air of the Senne river valley in Belgium. To dive into the microbial diversity in fermenting Lambic sour beer in a brewery in Belgium, the authors of “The Microbial Diversity of Traditional Spontaneously Fermented Lambic Beer” analyzed over 2000 bacterial and yeast isolates. They found a wide variety of bacterial species and only minor variation between batches. The authors also observed a pattern in the way the “bugs” changed during the fermentation process, which started with a mostly Enterobacteriaceae, replaced by Pediococcus damnosus and Saccharomyces spp. in the second month, and finally replaced at 6 months by Dekkera bruxellensis. Understanding the progression of “bugs” might allow breweries from around the world to replicate this region-specific fermentation process.

Published 4/18/2014, Image: Brakspear Oxford Gold Organic Beer by Christer Edvartsen

5. Latent virus reactivation in patients with sepsis

Reactivation of latent viruses may occur with prolonged sepsis. The authors of “Reactivation of Multiple Viruses in Patients with Sepsis” analyzed blood samples from critically-ill septic, critically-ill non-septic, and healthy patients to see if certain latent viruses—herpesviruses, polyomaviruses, and the anellovirus TTV—reactivated in these patients. The results suggested latent virus reactivation may be common with prolonged sepsis, consistent with development of an immunosuppressive state.

Published 6/11/2014, Image: Model of a Virus by Tom Thai

6. Prehistoric crocodiles may have dined on each other

The authors of “An Additional Baurusuchid from the Cretaceous of Brazil with Evidence of Interspecific Predation among Crocodyliformes” have discovered the fossils of a new crocodyliformes (crocodilians), Aplestosuchus sordidus, from the Late Cretaceous in Brazil.  Not only did the researchers find a new species, but they also discovered fossilized remnants of another crocodylian inside its stomach, suggesting that Aplestosuchus sordidus likely feasted on other crocodyliforms.

Published 5/8/2014, Image from the article

7. Microbes hitching a ride on the skin of a humpback whale

Humpback whales live in oceans around the world and the authors of “Humpback Whale Populations Share a Core Skin Bacterial Community: Towards a Health Index for Marine Mammals?” genetically sequenced over 500,000 bacteria collected from humpback whale skin from different geographical areas, as well as in various health conditions to explore the role these microbes play in their health. They found that in general, two bacterial species, Tenacibaculum and Psychrobacter, were hitching a ride on most healthy whales, but the overall composition of the bacterial populations differed depending on their various geographical locations, as well as on whether individual whales were stressed or deceased. These results indicate that scientists may be able to monitor these widespread whales’ health using microbes in the future.

Published 3/26/2014, Image from the article

8. Up close with 3D insects

Scientists working to develop a cost-effective method to create natural-color 3D models of insects in “Capturing Natural-Colour 3D Models of Insects for Species Discovery and Diagnostics” have used “off-the-shelf” equipment to image and model the insects in 3D. The 3D models are compact in size (~ 10 MB each); have excellent resolution; and can be embedded into documents and web pages, as well as mobile devices. The authors report that the system is portable, safe, and relatively affordable; complements existing imaging techniques; and opens up opportunities to use images of these delicate specimens for research, education, and art.

Published 4/23/2014, Image from the article

9. Mass extinction may not have resulted in slow recovery of prehistoric predators

Organism recovery after the end-Permian mass extinction is thought to have been slow, lasting up to eight million years or more. The authors of “Early Triassic Marine Biotic Recovery: The Predators’ Perspective” surveyed the global distribution and size of Early Triassic and Anisian marine predatory vertebrates—fishes, amphibians and reptiles—to take a closer look at organism recovery after the mass extinction event. Scientists observed no significant predator size increase from the Early Triassic to the Anisian, as would be expected with slow or stepwise recovery. These results likely indicate that from the Early Triassic onward, marine ecosystems were comprised multiple trophic levels.

Published 3/19/2014, Image from the article

10. Let’s study lions, tigers, and bears (and more?)

Scientists work hard to understand the role carnivores play in ecosystems, but all carnivorous species may not receive the same amount of attention. To investigate further the patterns in carnivore research, the authors of “Correlates of Research Effort in Carnivores: Body Size, Range Size and Diet Matter” combined bibliometric information they obtained from ~16,500 published papers on the Order Carnivora, a well-known group of nearly 300 species. The researchers found that scientists tend to study carnivores with large bodies and large geographic ranges, like bears and walruses, moreso than species with greater adaptability and broader diets.

Thank you for taking a moment to enjoy these PLOS ONE papers from the past four months. We’re looking forward to next list and meanwhile, you may explore our ALMs report to make your own lists.

* This list will be selected each month from a report of papers generated based on the following ALMs ratio: PDF downloads/HTML ratios.  Only papers published within the last four calendar months were eligible for inclusion. (This list was pulled from March 15, 2014- July 15, 2014)

First image: Llegó el verano – Summer is here by Guillermo Viciano

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I Smell Green, You Smell Blue

Color Palate

In elementary school, we all learn about our five senses: taste, smell, touch, sight, and sound. Together, they continuously provide us with massive amounts of sensory input. One way we make sense of all this is by forming associations: between sights and smells, feelings and tastes, and so on. For instance, we may associate the sound of waves to the smell of the ocean, the feeling of sand between our toes, or a salty taste. But to what extent do sensory associations change based on where we are from, and to what extent are they universal? It turns out that two people from opposite sides of the globe may draw very different connections from the same stimulus. That’s according to the authors of new research published in PLOS ONE, who investigated how people from different parts of the world associate colors with smells.

The researchers divided study participants into six populations based on geographic categories: Dutch, Netherlands-residing Chinese, German, Malay, Malaysian-Chinese, and US residents. Participants smelled a series of scents—14 total, including smells like “meat,” “soap,” and “burnt”—and were subsequently asked to choose from a palate of colors which one they most closely associated with the smell.

Odor-color associations chosen by the different groups

After the experiments were performed, the researchers compared the smell-color associations of individuals within each groups, and then compared the results between groups. While people from the same geographic group tended to make similar smell-color associations, color choices differed significantly between the cultural groups.  Some smell-color associations were generalizable across groups.  For instance, participants who smelled a “fruity” odor largely picked a pink or red color, and people chose oranges and browns for the “musty” smells.  The most similar groups to each other were the US and Germany, and the Germany and Malay samples.  Overall, the Malay group’s color choices were the most different from all the others. The authors had also predicted that the geographically-close test groups would lead to similar smell-color associations, but that didn’t appear to be borne out by the data.

So, what may be happening when someone smells a scent, and then chooses a corresponding color? The authors offer several possible explanations of what could be at work:

  • There could be an underlying neural basis for the association of reds and pinks with fruity smells that lead people to associate the two. In other words, the associations are inherent and that’s just how our bodies and our brains work.
  • There could also be a statistical correspondence, which means that a particular color and smell often accompany one another. Example: “I see red and I smell fruit… perhaps the two are related.” Over time, these patterns may start to leave their mark on our brains.
  • Sometimes people make strong associations with colors and words (perhaps “sky” and blue), called semantically mediated correspondences. Language and how it is used can influence these associations, so this experiment was designed to use as few words as possible to minimize language-based associations.

In this particular study, the authors suggest that the variation between the different cultural groups may be evidence that color-smell associations are not inherent or universal, but are informed by other factors that could include culture, language, and experience. More work remains to better understand all the factors that influence these connections, but for now, it seems that the color of a smell may depend on where you’re from.

Related links:

The Color “Fruit”: Object Memories Defined by Color

From Understanding to Appreciating Music Cross-Culturally

Which Colors Do You Smell?

Reference: Levitan CA, Ren J, Woods AT, Boesveldt S, Chan JS, et al. (2014) Cross-Cultural Color-Odor Associations. PLoS ONE 9(7): e101651. doi:10.1371/journal.pone.0101651

Images: The images come from Courtney Rhodes via Flickr and Figure 2 of the published paper

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Sharing is Caring: Varied Diets in Dinosaurs Promoted Coexistence


Everyone loves a good dinosaur discovery. Though they’re few and far between, sometimes we get lucky, finding feather imprints, mohawks, or birthing sites that reinvigorate public interest and provide bursts of insight about how they ruled the Earth before our arrival.

Dinosaurs must have been doing something right because they coexisted for millions of years, much longer than we humans have even been on the planet. In an article recently published in PLOS ONE, University of Calgary researchers studied markings on dinosaur teeth to determine how a diverse group of megaherbivores—plant-eating species whose adults weighed in at over 1,000kg—was able to coexist in Canada for at least 1.5 million years. The authors’ findings suggest that these dinosaurs managed to last so long by eating things that the others didn’t, thereby reducing competition for food and promoting a more harmonious (if dinosaur life could be considered so) coexistence.

The authors of this study started by taking a look at general tooth shape and any markings visible to the naked eye before moving onto examine the microscopic markings on teeth. The presence of certain small shapes or marks on teeth may indicate what type of food an individual ate during its lifetime, and can be analyzed using a technique called microwear analysis. As you might guess, foods with different textures or hardness leave different markings on our teeth. For instance, pits in the teeth suggest consumption of hard foods like nuts, while scratches are linked to the ingestion of tough leaves or meat. A combination of both reflects a varied diet.

The researchers analyzed a group of 76 fossils from 16 species in three ancestral groups, focusing on teeth still connected to skulls to provide more accurate species identification. These three groups lived together during the Cretaceous period in the Dinosaur Park Formation of Alberta, Canada, which at that point was on an island continent called Laramidia.


Ankylosaur Teeth

Ankylosauria, whose teeth are seen above, were a group of armored, stocky dinosaurs. One subgroup, the ankylosaurids, had small, cusp-like teeth (marked A) good for eating fruits and softer plant tissues, while another, the nodosaurids (marked B), had blade-like teeth useful for tougher and more fibrous plant tissues. Microwear analysis showed no significant difference between these two subgroups, meaning that, despite differences in general tooth shape, results indicate that their diets did not differ significantly. The evidence of both pits and scratches on their teeth suggests that both ate a variety of fruits and softer foliage.


Hadrosaurid Teeth

Hadrosauridae—identifiable by their duckbill-shaped face—had similar microwear to the Ankylosauria, suggesting that they also had a generalized diet, though their broad teeth, likely used for crushing food, may have made it easier for them to consume all parts of targeted plants, including stems and seeds, than the cusp or blade-like teeth found in the Ankylosauria.


Ceratopsid Teeth

Ceratopsidae, a family of thick-skulled, horned dinosaurs, including the well-known Triceratops, had teeth that functioned as shears, suggesting that they consumed particularly tough plants. Microwear analysis supports this idea, indicating more scratches than pits, and showing that these dinosaurs may have subsisted on mainly rough foliage, like twigs and leaves.

The evidence provided by microwear analysis, incorporated with other known facts about these species, such as height, skull shape, and jaw mechanics, helps paint a broader picture of the dinosaur food scene in Laramidia, and supports previous research suggesting that the varied diets allowed these large species to coexist for 1.5+ million years. Maybe we can take some cues from them to make sure we are at least as successful. Fingers crossed no meteors come along to ruin our chances.

Citation: Mallon JC, Anderson JS (2014) The Functional and Palaeoecological Implications of Tooth Morphology and Wear for the Megaherbivorous Dinosaurs from the Dinosaur Park Formation (Upper Campanian) of Alberta, Canada. PLoS ONE 9(6): e98605. doi:10.1371/journal.pone.0098605

Image 1: Triceratops prorsus skull by Zachi Evenor

Images 2-4: Figures 1, 9, and 6 from article

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