“Dinosaurs have become boring. They’re a cliché. They’re overexposed” – Stephen Jay Gould
Dinosaurs have always been inextricably linked to popular culture. Despite going extinct 65 million years ago at the end of the Cretaceous period they pervade our society. Dinosaur exhibits are the main attractions of natural history museums and outside of this setting, they can be found in films, documentaries, books, toy shops etc. A new discovery of one of these animals frequently adorns our newspapers. Even the word dinosaur has entered our everyday language as a metaphor to describe something as hopelessly outdated. Because of this pervasiveness there seems to be an implicit assumption among science communicators that dinosaurs “sugar-coat the pill of knowledge” but I’ve often wondered about the exact role these animals play in helping scientists communicate their subject. Perhaps they’re viewed by the public as little more than monsters, no more educational than dragons or the abominable snowman.
The well known science populariser and palaeontologist Stephen Jay Gould wrote an article about the nature of ‘Dinomania’ for the New York Review of Books around the time of the release of the film version of Jurassic Park. His article is wide ranging, exploring how dinosaurs have become so popular and asking if the excitement surrounding them at that time was just a fad; the result of cynical commercialisation. The most pertinent point he raises is the effect that such commercialisation has had on science communication efforts, “ In the past decade, nearly every major or minor natural history museum has succumbed (not always unwisely) to two great commercial temptations: to sell many scientifically worthless, and often frivolous, or even degrading, dinosaur products in their gift shops; and to mount, at high and separate admissions charges, special exhibits of colorful robotic dinosaurs that move and growl but (so far as I have ever been able to judge) teach nothing of scientific value about these animals.” He concedes that such animatronics would be useful if they were integrated with other educational exhibits but bemoans the fact that they are often separated from the rest of the exhibit entirely.
A further point he raises is that of the antagonistic relationship that has resulted from ‘dinomania’. He explains how, “Dinomania dramatizes a conflict between institutions with disparate purposes—museums and theme parks. Museums exist to display authentic objects of nature and culture—yes, they must teach; and yes, they may certainly include all manner of computer graphics and other virtual displays to aid in this worthy effort; but they must remain wed to authenticity”.
But if we look at the history of dinosaurs they ‘escaped’ into the public sphere almost as soon as they were discovered. They were never contained solely within the purview of science and scientists. The Victorian anatomist Richard Owen who gave dinosaurs their name collaborated with the artist Benjamin Waterhouse Hawkins in creating the first models of these animals. The Great Exhibition of London at Crystal Palace in 1854 displayed these sculptures to the public who were astounded. Pictures, posters and replicas of the sculptures were made available to the public. Certainly, commercialisation was no recent addition.
And 22 years after the release of Jurassic Park dinosaurs are still as prominent as ever, so it seems ‘dinomania’ was no flash in the pan. My own view is that these animals are an excellent means of showing the wonder of science and nature to people, often acting as a gateway to science especially among children. Yes they may be cynically marketed and there are many inaccurate representations of dinosaurs but undoubtedly even these have evolved. The Tyrannosaurus of Jurassic Park is a much more accurate representation of the animal than the version who fought King Kong 60 years earlier. It appears that dinosaurs are well-placed to both educate and entertain with neither component mutually exclusive. The final words go to palaeontologist Bob Bakker:
“Interest in dinosaurs is not a fad. Dinosaurs are nature’s special effects, extraordinary monsters that were created not by a Hollywood computer-animation shop but by the natural forces of evolution.”
Film directors often call on scientific experts to lend some legitimacy to their production. A recent, notable example was that of the theoretical physicist Kip Thorne advising Christopher Nolan on the realism of the physics in Interstellar. I think directors ask for the counsel of scientists in cases where they seek to make a film with at least one foot in reality rather than an outright fantasy. In Jurassic Park, a more biologically relevant movie, director Stephen Spielberg had noted-palaeontologist Jack Horner instruct the production team of the latest findings in dinosaur biology. The book and film of Jurassic Park had a significant effect on the public perception of dinosaurs coming as they did in the wake of the dinosaur renaissance of the 80s where the animals were reappraised as fleet footed, intelligent creatures. This was a radical departure from the image of tail dragging sluggards common in the early part of the 20th century (see King Kong). For instance, Horner was quick to quash the idea of a snake-like forked tongue for the Velociraptors. This was a great example of science and art working together in symbiosis. The film was a box office success and the public consciousness was updated to have in mind a more accurate image of what dinosaurs were really like. Of course the film wasn’t perfect in its representations and nitpickers had plenty of grist for their pedantic mills, but overall both ‘sides’ were happy.
But now the release of the trailer for the 4th film in the series, Jurassic World, has caused consternation among palaeontologists. It’s clear from the footage that the dinosaurs haven’t evolved along with the science as they did with the first film. Mainly, that means no feathered animals; perhaps the studio executives weren’t convinced that a fluffy Tyrannosaurus could induce as much panic in an audience. Capturing the disappointment in the scientific community, John Conway writes, “Of course we realise it’s a film – but we also recognise the power it will have to shape people’s ideas about prehistoric animals. And in Jurassic World’s case, it looks like we’re getting a very dull monsters trope. ” This leads to the question as to what does Hollywood owe science? It’s a hard one to answer because there’s no moral imperative for a director to follow the strictures of scientific fact exactly. James Erwin says “The truth is that science fiction is, first and foremost, fiction—and that’s how it should be judged.” I agree with this to an extent, in that if a director is striving to give a message and has to break away from scientific reality to achieve this than so be it. Think of something like the ability of characters to invade dreams in Nolan’s Inception. Nevertheless in the case of Jurassic World I’d bet we’re going to get yet another discussion of man’s hubris , a trope that has been reiterated throughout the Jurassic Park series. If they were able to do this while creating the most realistic dinosaurs at the time in 1993 I don’t see why they couldn’t continue to do so in 2015. Maybe it just rankles with me that we’re seeing another edition in a series of diminishing returns and I should check my hopes. I wonder what other people think of this? But it’s still frustrating for me. Lost World? More like Lost Opportunity.
He’s back! Originally a metaphor for the horrors of the bombing of Hiroshima and Nagasaki in a heavily censored post-war Japan, Godzilla become a cultural icon whose name is known across the world. His latest incarnation is in Gareth Edward’s film which I saw on its opening weekend. And as a biologist I can’t help but watch with an eye towards the plausibility of the gigantic reptile and his opponents.
I was pleasantly surprised to find that, like Edward’s previous film Monsters, care had been taken to ensure that the titular creature and his adversaries had realistic behavioural traits. Of course, we are dealing with animals 100m tall so some artistic licence is being taken, but I was impressed with how the creatures had clearly been considered as biological organisms and I thought would be fun to discuss the monsters of Godzilla from a biological perspective. I will have to include some minor spoilers so do not read unless you have seen the film or don’t care. You have been warned!
Despite being the titular subject of the film, Godzilla is arguably not the protagonist though he is undoubtedly the saviour. The catalyst for the action is the birth of a MUTO. or Massive Unidentified Terrestrial Organism. It is soon apparent that the “terrestrial” part of its name is a misnomer as it takes to the skies upon gigantic wings. A second MUTO is discovered, though this time the term “terrestrial” holds true. This animal is also significantly larger than the first one and the scientists quickly recognise that rather than these being two different species, they are a male and female of the same species. The male is a highly mobile but smaller creature while the female is a much larger and less mobile animal.
This sexual dimorphism is common in the animal kingdom. We are used to thinking of males as the larger sex but this generally only occurs in territorial or polygamous animals where size is important in attracting and maintaining females. In species where these factors are not important females are often larger as they have a larger reproductive burden. Males can produce vast quantities of sperm at even relatively small sizes while the number of eggs a female can produce is directly related to her size. The larger a female can get, the more eggs she can produce. This type of sexual dimorphism is common in insects, spiders and fish and occurs occasionally in other taxa including mammals such as the spotted hyena and blue whale. Probably the most extreme example of this sexual dimorphism is seen in Ceratoid anglerfish, a family of deep sea fish whose low densities mean that finding a mate can be extremely difficult. To get over this problem the males have become parasitic, attaching to the first female they find and slowly lose their internal organs as their circulatory systems merge with that of the female. Their body atrophies until they are little more than testicles, ready to fertilise the female whenever she requires.
Female ceratiid dwarfing her male companion http://bit.ly/1n8Fx68
The smaller size of the males means that they are often more mobile than the females. Indeed, flightless females and volant males are not a construct of the film but are found in real life too. Scale insects and stick insects, among others, have this dichotomy of locomotive strategies. The larger an animal is, the more energetically costly it is to defy gravity. In addition, flying can open up the possibilities of predation. It is therefore safer for females to remain relatively sedentary and wait for males to come to them. In order to seek out as many females as possible, travel must be energetically cheap for the male. This means covering as much ground as possible which is easiest if they can fly which means being light. This is seen in the film as the male travels across the entire Pacific ocean in less than the time it takes the female to travel from Nevada to San Francisco.
The male MOTU attracts the female through the use of vocalisations: he calls to her. In the animal kingdom, too, it is predominantly the male who calls to attract females. From cicadas to penguins , males across the animal kingdom use their voice to tell females how great they are and what excellent genes they have. Blue whales have calls that can cross oceans so the male MUTO’s call to the female that crosses the Pacific is not inconceivable, though how it then travels across land to Nevada is stretching plausibility somewhat.
When the MUTOs finally meet they engage in a bonding ritual commonly seen in species who pair-bond. Species such as penguins and albatrosses, where pairings are maintained across more than one season, have ritual greetings that reaffirm their bonds. The MOTUs have so far been insectoid in their behaviour so this may seem out of keeping as pair bonding is commonly found in warm blooded animals. Yet there is an insect that pair bonds, the Lord Howe stick insect, although the female is also capable of reproducing through parthenogenesis. This may explain why we don’t actually see the MOTUs mate before the female lays eggs: she is capable of reproducing parthenogenetically. There are some species which are parthenogenetic but still require sperm to stimulate egg production. While we clearly see the female carrying eggs prior to her meeting the male, it may be that contact with the male, however brief, is required to stimulate egg laying.
Before the laying of eggs and after the pair bonding comes the gift giving. Nuptial gifts are common in the animal kingdom across many taxa. Sometimes these gifts come in the form of packages of highly nutritious sperm which the female eats, often while the male mates with her. The larger the gift, the longer she eats and the greater the chance she has of fertilising the eggs. In other species the gift is in the form of food the male has captured. It is this type of nuptial gift that the male MUTO offers the female, in the form of a nuclear bomb. Whatever rocks your boat!
The final two behaviors we see are nest guarding and emotion. The female MUTO protects her nest from Godzilla and shows grief and anger when her nest is destroyed by our plucky human protagonist. Many animals guard their nests and offspring. We are used to seeing mammals and birds protecting their young but this behavior is also present in insects, spiders and fish among others. For some animals, such as the octopus, this nest guarding is fatal as they are so dedicated to their protective role that they do not leave, even to eat, while the eggs develop. The grief that the female expresses is also seen in real life, though so far it has only been seen in mammals and birds. However, given the level of intelligence shown by the MUTOs, grief is not an inconceivable reaction.
The behaviours exhibited by the MUTOs are surprisingly biologically plausible. In a genre where science is often used only as far as necessary and scientific words are often thrown around without any consideration as to their suitability it was a surprise to see so much care going into these animals. This is not to say that everything about the creatures was accurate. Godzilla is 100m tall, the female MUTO is similar in size and the male, while smaller, is still several storeys tall and is capable of flight. A recent discovery of the largest dinosaur to date, a titanosaur from Argentina, was ‘only’ 20m tall and weighed just under 80 tonnes. The reason animals do not attain the size seen in fiction is a combination of the effects of gravity and the strength of organic materials. As animals get bigger their volume grows faster than their length and this puts increasing pressure on their skeleton. There is a size above which it is impossible to function and it is unlikely that anything larger than the recent dinosaur discovered will be significantly surpassed. Godzilla and his kaiju compatriots are fortunately physically impossible on our planet. Equally, their diet is implausible and raises the question of why, if they can absorb radiation, do they need mouths? The characteristics of Godzilla himself are even less biologically sound, but many of his most egregious characteristics date back to his creation, when creating a powerful metaphor for violent destruction was more the more pressing concern.
That’s one big dinosaur! See the BBC news article http://bbc.in/1mG5oE0
Giant monsters are a staple of genre fiction and, like the transporters of Star Trek or the time travel of the Terminator films, if you cannot suspend your disbelief in that regard then you’d better not watch. But often it is the case that you are willing to suspend some disbelief but then the writer or director expects you to go further and asks you to throw any desire for realism out of the window. The pleasant surprise with this film is the effort the filmmakers have made to make their creatures feel real. They looked amazing, moved realistically and, most surprisingly of all, behaved realistically. I hope that this is the first of many films that exploit the amazing diversity of real life to their advantage, rather than make things up. When real life is so diverse and bizarre, why bother with fiction? Save that for the plot!
Author: Sarah Hearne, hearnes[at]tcd.ie, @SarahVHearne
As mentioned previously on the blog, Andrew Jackson and I started a new module this year called “Research Comprehension”. The module revolves around our Evolutionary Biology and Ecology seminar series and the continuous assessment for the module is in the form of blog posts discussing these seminars. We posted a selection of these earlier in the term, but now that the students have had their final degree marks we wanted to post the blogs with the best marks. This means there are more blog posts for some seminars than for others, though we’ve avoided reposting anything we’ve posted previously. We hope you enjoy reading them, and of course congratulations to all the students of the class of 2014! – Natalie
Here’s Kate Minogue and Rosie Murray’s blogs inspired by Professor John Hutchinson‘s seminar, “Six-toed elephants and knobbly-kneed birds! Case studies in the evolution of limb sesamoid bones.”
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Them bones them bones need………investigating!
Kate Minogue
When a seminar begins with a stuffed cat photo-bombing with the crowd you know its not going to be your usual type of research seminar, and what John Hutchinson discussed during his talk in Trinity College Dublin was far from the norm. The acclaimed scientist and author of the hugely popular blog “What’s in John’s freezer?” kept the audience intrigued throughout. From six-toed elephants to two-knee-capped birds the diversity of sesamoid bones was dealt with in great detail and, more importantly to an audience of previously oblivious zoologists, their evolution over time gave us some amazing new insights.
Firstly I think its important to begin as Hutchinson himself did. By explaining what a sesamoid bone is. They are essentially small, rounded masses embedded in certain tendons and usually related to joint surfaces. They can be found in the knee, hand, wrist and foot of the human body. Hutchinson himself explained them as a waste basket of bones that “ sit in funny places”. By looking at different species which possess these bones in certain locations, Hutchinson began investigating their function and the role they play in locomotion ability. It was through his work in this field that these small, awkwardly located and previously misunderstood bones were credited with giving greater mechanical advantages to an organism by allowing a change in direction of muscle force.
The most interesting part of Hutchinson’s work, from my point of view, was his research on elephants’ feet. By looking deeper into the composition of the foot of present day elephants and past remains he was able to highlight an evolutionary change that has occurred over millions of years. Looking at an elephant you would consider them to be very flat footed animals. However Hutchinson’s research proved this observation to be incorrect. By dissecting present day elephant feet (from that famous freezer of his) he was able to show that they are in fact pointed-toed animals. At the rear base of their foot they have a mass of fat which causes the bone structure of their foot to be tilted ( almost as if they were wearing a high wedge made out of fat). But it was what he found within this mass of fat that make this unlikely foot structure functionally possible. He identified a sesamoid bone embedded within, which was acting as a sort of prop along with the cushion of fat. This bone was later referred to as a pre-digit as it has lost its tendon connections over time and now acts more like projections from the base such as digits. The adaption of the sesamoid bone in the foot of the elephant over 40 million years ago has allowed elephants to change their posture from a once flat footed animal to a very unusual large mammal with a tilted foot presumably giving the animal better mobility.
The panda is another example that Hutchinson touched on to highlight the use of a sesamoid bone to increase mobility. Instead of evolving an opposoble thumb to aid in grasping bamboo and feeding they use an enlarged sesamoid bone to act as a thumb instead. This adaption has fulfilled its role perfectly and allowed pandas to continue to feed on their exclusive food source, as long as it exists.
Leaving Hutchinson’s seminar I found myself questioning what else we are misunderstanding in the animal kingdom. How have these sesamoid bones which appear to have a huge role in mobility and muscle function pretty much escaped our attention till now and what else are we missing? Hutchinson’s work is a clear example that if you question the unlikely you could just discover something unexpected. Who would have thought it, a 6-toed, high-heels-wearing large mammal! It just doesn’t get better than that, or does it….?
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HOW does the chicken cross the road?
Rosie Murray
While a chicken’s reasons for crossing a road have long been fodder for comedians (the not-so-funny ones), science is less concerned with its motives, and more with its locomotives (that is, HOW chickens cross roads).
Locomotion in modern birds (Neornithes) has two remarkable features; feather-assisted flight and unusually crouched hindlimbs, for bipedal support and movement. I will focus on the issue of crouched hindlimbs.
As has been known for decades, modern birds are dinosaurs (even comparatively rubbish birds like chickens). So, the way birds – living dinosaurs – move is obviously a vitally important source of data for understanding how locomotion worked in extinct dinosaurs.
But birds have some unusual features that set them apart from all the other dinosaurs. A major difference is that birds don’t really have tails, or, if they do, they’re fairly negligible, feathery things. We know that all the other dinosaurs had really big, long, meaty tails. So, somewhere on the way to birds, the tail became so reduced in size that it has almost been totally lost.
The vast majority of land animals, including ourselves, move forwards by swinging the entire leg back-and-forth from the hip (hip-driven locomotion). However, birds keep their hips extremely bent; pointing their thighs forwards, and move around mostly by swinging the lower leg from the knee (knee-driven locomotion). This bent hipped, knee-driven style of moving gives them a characteristic “crouched” look.
But, let’s start at the very beginning. In order to move, terrestrial animals exert a force against the ground to support and then move their body. The reaction force of the ground (GRF) is directed at, or close to, the centre of mass (CoM). This stabilizes the body as it moves position. The GRF is mainly vertical during the mid-phase of locomotion. The mid-phase is when the hindlimb is poised beneath the body on its way forward. Bipedal animals such as birds use a single supporting limb for most of this stance. Therefore the foot of this limb must be placed directly underneath the CoM to exert the vertical GRF. The joints of the limb must also be suitably positioned so that the antigravity muscles can push against the ground in such a way as to move forward without losing balance. The location of the CoM is therefore a major determinant of the limb orientation at mid-stance (Fig. 1)
Fig. 1: Living tail-less dinosaurs (A) such as chickens have a centre of mass (black/white) located far forwards in the body. To cope with this they keep their feet forwards by bending their hips and swinging the leg from the knee, which is very unusual. Extinct dinosaurs with large tails (B) would have a more rearward centre of mass. This means they may have had stood straighter and swung their legs from the hip, like most other animals. Image source: The Guardian
Losing the tail means that relatively more of a bird’s mass is at the front of the body, resulting in a more cranial CoM. To remain balanced, the feet and legs also need to be placed further forwards. And, one consequence of the crouched, knee-driven way birds walk and run is that the leg joint that does most of the job (the knee), can be stuck a lot further forwards on the body than the main joint other animals use (the hip). So a lot of the weirdness of bird locomotion may just be related to them having to put their legs more towards the front of the body, to match the CoM.
To test this, a team of scientists lead by Bruno Grossi took a simplified approach to the question, and stuck a big heavy tail on a chicken’s backside to mimic the stature of dinosaurs. And the CoM moved back, just like that. The chickens responded by straightening their legs and swinging their hips more, just as their dinosaur ancestors are hypothesized to do. If you’re interested in reading Gossi’s paper, you can find it here.
The current trend in this kind of research is towards more technical methods; using computer models to digitally reconstruct movement using every muscle, tendon and bone possible. Professor John Hutchinson and his team are doing exactly that. And their findings unarguably agree with Gossi’s very simple experiment, that the CoM of modern birds has moved forward, and brought with it, the ‘crouched’ stance that we see in the modern day chicken and its relatives.
So, how does the chicken cross the road? Well, as always in science, we can only say how does the chicken NOT cross the road? Not like a dinosaur (Fig. 2…not to scale!).
Well, mainly because it’s costly to climb when you’re an animal of that size. A previous study estimated that a 4 tonne elephant would have to eat for 30 minutes to compensate for a 100m climb. Ideas man Graeme Ruxton and his co-author David Wilkinson develop this further in their new paper. They ask whether avoidance of hilly areas is to be expected in general for animals of a large mass such as the sauropods. These are the long-necked dinosaurs that were the largest terrestrial animals that ever existed. Some of the upper mass estimates of, albeit poorly described, species are over 100 tonnes! Using simple scaling relationships relating to the energetics of movement, food intake etc. Ruxton and Wilkinson show that as a herbivore increases in size the fraction of time spent eating to balance the cost of climbing will increase. In the case of sauropods we can look to the fossil record for support and it does show the creatures preferred flat environments such as fluvial plains. Their footprints and nesting sites are often preserved in these areas. Of course, energetic concerns aren’t the only issue stopping these animals from populating the hills. The danger of falling would be much higher on a friable surface and the bigger you are…
Any thoughts of regaining your energy on the way down after a costly ascent can be dispensed with. An animal must expend energy to control the rate of descent especially to avoid falling. One benefit of being large is that you have energy reserves so it is possible to travel into the hills if absolutely necessary but these forays would be infrequent.
This result suggests steep areas should be depauperate with respect to larger herbivores. We could imagine highland islands of smaller herbivores alongside plants which are free from the pressures of huge plant-eaters. The conclusion of the paper asks us to explore extant ecosystems for such a pattern. This could be extended to Mesozoic ecosystems. Perhaps there would be an ontogenetic niche shift in the sauropods, moving from hilly areas to the flatlands as they developed.
On the 20th and 21st of February we had our annual School of Natural Sciences Postgraduate Symposium. Over the course of two days many of our PhD students presented their work to the School. We also had two interesting plenary talks from Dr Sophie Arnaud-Haond (Ifremer) and Dr Lesley Morrell (University of Hull). Unfortunately our third speaker, Dr Fiona Jordan (University of Bristol) had to cancel due to illness.
For those of you who are interested in exactly what we work on here at EcoEvo@TCD, here are the abstracts from the PhD student presentations. Check out the TCD website for more details!
Aoife Delaney: Eco-hydrology of humid dune slacks*
*Highly commended
Dune slacks are hollows in coastal sand dune systems where the groundwater table is close to the surface. Many dune slacks flood in winter to form temporary ponds which can last from a few weeks to several months. Humid dune slacks are an Annex I habitat (2190) and in accordance with Article 17 of the Habitats Directive they have been mapped and assessed in Ireland on the basis of their vegetation. During monitoring in 2013, Humid dune slacks (2190) were assessed as Unfavourable-Inadequate and topics for further research were identified. The extent and effect of water abstraction and wastewater from recreation facilities has not been firmly established in Ireland, and work relating biological communities to water quality or depth and duration of flooding has focussed almost entirely on vegetation up until now.
This project will assess variation in vegetation, mollusc and water beetle communities present in dune slacks in Donegal, Mayo, Kerry and on the east coast. It will also investigate the effects of land management by comparing biological communities of sites which are under different management regimes such as extensive pasture and golf courses. The hydrological functioning of dune slacks will be related to biological communities they support.
Anne Dubearness:Systematics of the genus Embelia Burm.f. (Primulacae — Myrsinoidae)*
*Highly commended
Primulaceae subfamily Myrsinoideae is a species-rich tropical group containing over 2000 species, with several taxonomically difficult genera with poorly defined limits and many novelties needing description. Within the subfamily, Embelia is a genus of climbing shrubs distributed mostly in South and South-East Asia and tropical Africa. The last monograph of this genus (made by Mez in 1902) recognised 8 subgenera and 92 species, but the total number of species is currently estimated at 140. The systematics of this group needs investigation using a modern phylogenetic approach: indeed, Embelia displays extensive morphological variation (especially regarding the position, shape, size and merosity of the inflorescences) and is only distinguished from other Myrsinoideae by a climbing habit and distichous leaves. This project aims to combine molecular and morphological data in order to investigate the systematic of Embelia at 3 levels: first of all the monophyly of the genus must be tested, then the existing subgenera must be assessed and refined in order to produce a taxonomic framework of the genus, and the final focus will be on the subgenus Euembelia Clarke, which contains more than 65 species and could certainly be split into several sections.
Thomas Guillerme: Combining living and fossil taxa into phylogenies: the missing data issue*
*Highly commended
Living species represent less than 1% of all species that have ever lived. Ignoring fossil taxa may lead to misinterpretation of macroevolutionary patterns and processes such as trends in species richness, biogeographical history or paleoecology. This fact has led to an increasing consensus among scientists that fossil taxa must be included in macroevolutionary studies. One approach, known as the otal evidence method, uses molecular data from living taxa and morphological data from both living and fossil taxa to infer phylogenies. Although this approach seems very promising, it requires a lot of data. In particular it requires morphological data from both living and fossil taxa, both of which are scarce. Therefore, this approach is likely to suffer from having lots of missing data which may affect its ability to infer correct phylogenies. Here we assess the effect of missing data on tree topologies inferred from total evidence supermatrices. Using simulations we investigate three major factors that directly affect the completeness of the morphological part of the supermatrix: (1) the proportion of living taxa with no morphological data, (2) the amount of missing data in the fossil taxa and (3) the overall number of morphological characters for all of the taxa.
Florence Hecq: Effects of scale and landscape structure on pollinator diversity and the provision of pollination services in semi natural grasslands
Over recent decades, humans have been changing the environment more rapidly than in any other period of history. Technological advances and new agricultural policies have led to a simplification of landscape structure resulting in the loss and fragmentation of habitats for flower-visiting insects which play an important ecological role as pollinators. Pollinating insects are very mobile and are influenced by the availability of flowers and nest sites over a scale of several kilometres.
In this study, we investigated the effects of the complexity of landscape structure on the diversity of four pollinating taxa and on the provision of pollination services to four plant species. Pollination data were collected in 19 semi-natural grassland sites in north midlands region of Ireland and related to the composition and configuration of surrounding landscape at two spatial scales (500m and 1km radius around sampling sites). Landscape structure was characterised by digitising each landscape feature with aerial photographs and GIS, and then ground-truthed using field-based surveys. Knowledge of these pollination/landscape scale relationships is crucial for a better understanding of pollinator diversity patterns and should be helpful for future conservation management decisions; ensuring essential levels of pollination services to wild plants are maintained.
Lindsay Hislop: Does nutrient enrichment moderate the effect of water level fluctuations on littoral communities?
Freshwater abstraction from lakes in order to support a growing human population is rapidly becoming a major global stress on lacustrine ecosystems. The consequent amplification of water level fluctuations disproportionately impact lake littoral zones, which contain the majority of their biological diversity. However, remarkably little is known about the impacts of amplified water level fluctuations on littoral assemblages and less still is known about how they interact with nutrient enrichment, one of the most pervasive and important of human disturbances on the biosphere. To address this, we established an experiment in large outdoor pond mesocosms where we quantified the effects of water level fluctuations and nutrient enrichment, both separately and together. We found that the impacts of water level fluctuations on both primary producers and benthic consumers varied significantly along the depth gradient. However, we found no interactions between nutrient enrichment and water level fluctuations. Given that the problem of amplified water level fluctuations is likely to be exacerbated considerably by predicted increases in climatic variability and enhanced water demand, our findings have profound implications for the conservation and management of global aquatic biodiversity.
Nuria Valbuena Parralejo: The impact of artificial sub-surface drainage on greenhouse gas emissions, change in soil carbon storage and nutrient losses in a grazing cattle production system in Ireland
In Ireland, over the 33% of milk is produced on a Heavy Soils farms. Heavy Soils are characterised by low permeability and often form in high rainfall areas. The combination of both can lead to waterlogging, promoting soil compaction which significantly affects the grass production. Drainage has been shown as an effective tool for improving the soil permeability. Little data is available to assess the effect of the artificial subsurface drainage of a grassland production system, on greenhouse gas emissions, change in soil carbon storage and nutrient losses. This experiment will be carried out in Teagasc Solohead Research Dairy Farm (latitude 52° 51’ N, 08° 21’ W; altitude 95 m a.s.l.). Different treatments (i) mole drain winter, (ii) mole drain summer, (iii) gravel mole and (iv) control were imposed in one site of the farm in 2011. A new experiment will be set up at a different site on the farm in summer 2014 with (i) control and (ii) gravel mole into collectors. Nitrous oxide (N2O) flux measurements, soil respiration measurements, soil total carbon and total nitrogen analysis, soil nitrogen mineralisation and net nitrification, water analysis, water table measurements and herbage production will all be perform in both sites over two years.
Adam Kane: Ontogenetic dietary partitioning in Tyrannosaurus rex*
*Highly commended
Obligate scavenging in vertebrates is a rare mode of life, one which requires very specialized morphologies and behaviours to allow the scavenger to cover enough area to find sufficient carrion. Yet, a number of studies have suggested that Tyrannosaurus rex occupied this niche with others arguing for its role as an apex predator. In this study we move away from the polarised predator-scavenger debate and argue that T. rex underwent an ontogenetic dietary shift, increasing the proportion of carrion in its diet as it aged due to both the increased availability of carrion through direct intraspecific and interspecific competition and also by exploiting resources unavailable to its smaller competitors, namely bone. We follow an energetics approach in our study to explore the effect of this previously unrealised resource on the ecology of T.rex and look at the impact of the proposed ontogenetic dietary shift.
Imagine you’re stuck in the desert, your plane has crashed and you’re trying hard to fix it. Then a child pops up out of the blue and asks you straight out “If you please – draw me a dino…”. Now let’s say you do as Antoine de St-Exupéry and take up the challenge without asking too many questions. How would you draw that dino? I guess it depends on when you were asked the question.
Let’s go back through the history of drawing dinosaurs. The pictures I grew up with were the ones from Jurassic Park who came directly from the last dino-revolution started by Ostrom and Bakker‘s work (especially with the publication of Dinosaures Heresies, in 1986). This vision was then heavily popularized by the three (nearly four?) blockbuster movies we all know and love…
Since the late 1990’s, the increased availability of formerly highly expensive techniques such as CT scans or synchrotrons, has helped to understand dinosaurs better than ever. Led by new discoveries from vast, previously unexplored deposits, some of the most interesting work from recent times shows an even closer link between birds and dinos than we previously thought (see last week’s Science NOW). So I believe (and hope) that the next generation will grow up with the pictures of dino-chickens and see their lunch time chicken wings as true theropod meat…
It is always really interesting to look at all the work that has been done and presented to the public through dinosaur pictorial art; from the weird/funny starts in the first half of the 19th century to the modern, highly accurate representations of today (the French artist Alain Bénéteau is just one example among many). As a nice example, have a look at the pictorial evolution of the second oldest scientifically described dinosaur: the Iguanodon.
But here I’d like to emphasize my love for what I think was the “golden age” of dinosaur pictorial art. I obviously want to refer to the work of artists like Charles R. Knight (1874:1953), Zdeněk Burian (1905:1981 – have a look at this awesome online gallery) or Rudolph F. Zallinger (1919:1995). Their beautiful and (for their time) highly accurate scientific artwork was crucially import for bringing palaeontology into the public eye. This “golden age” was made possible by the upgrading of palaeontology to the status of a true science and the general acceptance of Darwin’s theory. Public interest in palaeontology at this time was also fueled by new fossil discoveries from expanding European colonies and the American frontier eventually leading to the most epic palaeo-story ever: the Bone Wars (soon to be seen on HBO)!
I refer to this period (second half of the 19th century and first half of the 20th) as a “golden age” but that does not mean that it was the peak of palaeontological discovery or interest. Our palaeo-knowledge has never been richer. Dinosaurs are no longer merely unknown beasts from an ageless past. They are now placed in accurate phylogenetic frameworks and are just one of the many extinct tetrapod groups which we can now link to extant biodiversity. However, identifying birds as living remains of the dinosaur lineage does diminish dinosaurs’ mightiness. They are no longer the perfect romantic group of fossils: giant monsters that ruled the earth for over 150 million years before being completely wiped out by a single meteorite that cleared the way for us to evolve and exist. Even if I actively try to fight against this simplistic view of the History of Life, I have to admit that it is the one that brought me into palaeontology, not the chickens I used to keep in my parents’ garden… So, although I have no drawing talent whatsoever, because I think that dinosaurs are still awesome but lacking the mightiness they deserve, I’ll draw that little prince something like this:
A sketch from De la Beche (1930) titled: Dr M[antell] in extasies at the approach of is pet SaurianThis post was inspired by the excellent “Dinomania” chapter of Gould’s Bully for Brontosaurus 1991, by a master’s project done with F.Barbiere, S.Enault and B.Ramassamy and by the excellent blogs which can be found about this subject such as here, here or here.
Recently Science published O’Leary et al.’s – new load of oil to fuel the burning debate on the origins of placental mammals.
Just to be clear: there is an important distinction between mammals in general that includes many fossils from the Jurassic as well as the extant platypus, kangaroo and your grandma; and placental mammals that includes your grandma and the armadillo (but not kangaroos or the platypus) and no fossil before 65Myr. For readers that are not used to the debate concerning the first placental mammal here’s the main question: did the first placental mammals diversify before or after 65Myr (the important KT boundary)?
(1) After Katie
One view suggests that early mammals lived in the shadow of dinosaurs and the demise of these mighty creatures allowed our rat-like ancestors to take over the earth, the seas and the skies “Save yourself mammals”. This idea was proposed by Simpson in the 1950’s and is supported by the fossil record; many dinosaurs (both big and small) were present before the 65 Myr KT boundary, then a catastrophic meteorite impact marked the KT limit and placental mammals radiated after that. This sequence of events seems to be very straightforward but reality appears not to be so simple. Increasing numbers of mammal species from the late Cretaceous are being discovered, (including rather big ones feeding on dinosaurs) and not many species in general are found in the fossil record before 55Myr when all groups of placental mammals seem to suddenly appear (for a full story see Luo’s 2007 Nature review).
(2) Before Katie
In contrast, another group of people, mainly assisted by molecular dating methods, found out that post-KT placental mammalian diversification may just be an artefact of the fossil record (like Meredith et al 2011 in Science again). Their DNA evidence seems to say that placental mammals evolved before the KT limit and that either palaeontologists failed to find them or else the fossil record failed to preserve them. One major criticism that moderate people argue is that there are still problems associated with molecular dating methods. I won’t go into the details (yes I’m trying hard not to) but molecular dating relies on DNA on the one hand (sampling quality and modelling) and on the fossil record on the other hand. So if the people using DNA criticise the fossil record and want to improve the DNA dating estimates, they have to rely on the same fossil record that they are criticising. The snake bites his own tail.
So what about O’Leary and colleague’s paper? They basically support the first theory (placental mammals evolved after KT). Fair enough, it was led by a number of great palaeontologists and based on a massive morphological data set (~4500 characters introduced as phenomics (from the phenotype) as opposed to genomics (from the genome) data) collected on 40 unambiguous fossils and 46 extant placental mammals. Genomic data based on 26 genes of these extant placental mammals was also included. This paper is the result of an impressive and unique collaborative work, but – Ned Stark from Games of Thrones said “nothing someone says before the word “but” really counts” – but this paper is criticisable…
First of all, the data set: although the morphological data is impressive, the taxa sampling effort seems a bit weak, especially for extant placental mammals. Meredith et al used the same genomic data (26 genes) but based on ~164 mammals to answer the same question. Why couldn’t O’Leary use all of this already published mammal DNA? For the second criticism, I’m just going to quote Yoder’s review published in the same issue “Today, sophisticated theoretical and computational methods are used to estimate and calibrate molecular phylogenetic branch lengths (which represent time). Together with improved methods for integrating fossil and molecular data, dates derived from molecular phylogenies have inched closer to those implied by the fossil record. Is the approach used in the O’Leary et al. study directly comparable to these recent molecular phylogenetic studies? Not really, as it turns out.”
No wonder this paper supports the first theory, it is just a precise and massive analysis of the 40 species of the placental mammals fossil record. Personally, I’m really frustrated by how they managed to publish this paper. Since it’s part of my PhD research, I automatically get excited when I see fossils mixing with extant species so I really hoped this paper would link the two approaches instead of supporting the old fashioned view of evolution (the dinosaurs dying and the mammals taking over). I’d like to think that the history of life is a bit more complex and exciting…
A last comment to justify my title and which will be my main critique to this paper is that O’Leary et al. tried to recreate the “hypothetical placental mammal ancestor”.
As I said, this paper could be seen as a summary of the placental mammal fossil record. So why did they break the first rule that keeps palaeontology away from palaeo-poetry (i.e. going too far with palaeontological hypotheses)? Here they reconstructed a whole creature using their morphological data. What they made was essentially a mean (average) placental mammal (a primitive rat-like creature) – a throw-back to the early stages of palaeontological views of mammalian evolution. What did the ancestor of a duck and a beaver look like? Something in between – a platypus for example? As Olaf Bininda-Edmonds said on Ed-Yong’s Nature post “comparing the two estimates is like comparing “apples and oranges”, they haven’t really done anything to resolve this on-going dispute”.
This paper has also caused controversy on twitter. I’ll just cite two opinions.
Gavin Thomas (@Phalaropus)
“The reconstruction is fun – I’d love to see a picture based on 95% CIs for the ancestral states.”
and Rich Grenyer’s answer (@rich_)
“yes indeed. Something like this” (see our title image).
Many parts of the online science community got excited about this paper, you can see further discussions on Jerry A Coyne’s blog (here and here), on Ed Yong’s one (here and here or there) or else on the twitter feed #placental.
“Being a paleontologist is like being a coroner except all the witnesses are dead and all the evidence has been left out in the rain for 65 million years” Mike Brett-Surman, 1994
I am very much for palaeontology and the enthusiasm for the science today but there was a time when even the mighty dinosaurs were out of fashion. During the 40s and 50s they were thought of as animals who had been destined for extinction, little more than children’s monsters.
Perish the thought. That changed in both academic and public circles when palaeontologist John Ostrom and his student Bob Bakker came on the scene during the 60s and 70s. The trigger of this ‘dinosaur renaissance’ was Ostrom’s description of Deinonychus which he deemed a fleet footed, endothermic, bird-like animal. This was a world apart from the view of dinosaurs as cold-blooded, tail dragging, sluggards. In Bakker’s book, the Dinosaur Heresies, he presented a persuasive body of evidence to support the idea that dinosaurs were endothermic. Bakker is a great artist too and it really helped to get his point across. You can see his influence in the similarity of the Velociraptors of Jurassic Park infamy to his artwork. This was all very exciting. Now we had animals seemingly on a physiological par with mammals and birds. What I find so impressive is that we can still make inferences about the physiology of long extinct animals so long as we marshal enough evidence.
But the case for endothermy wasn’t so clear cut. The bones of reptiles and amphibians, which are demonstrable ectotherms, show seasonal bone growth and we can see similar patterns in the fossils of dinosaurs. An impasse presented itself.
Until now anyway. The issue, it seems, is that we weren’t looking in the right place. A recent paper in Nature shows why. The authors of the study looked at the histology of modern ruminant mammals revealing that they also display seasonal bone growth and that this can be extended to all endotherms with a constant body temperature. So seasonal bone growth can no longer used as an argument for cold blooded dinosaurs. I think it’s interesting that all it took was for someone to look at modern mammals.
Mathematics is the language of science and when it comes to biology this is no exception. It’s only when you start researching for yourself that you realise how useful a skill it is. Consider, for example, the mathematical approach that Graeme Ruxton and collaborators bring to their research in ecology and evolution. Ruxton has addressed questions ranging from the foraging radius of vultures to a hypothesis proposing that sauropod dinosaurs produced enough methane, a la modern cows, to affect the climate of the time. The latter paper does seem to ask an intractable question on first inspection given that the animals have been extinct for at least 65 million years. So how do the authors even begin to tackle their question?
Mathematically of course. To begin, they estimate the population density of sauropods during the Jurassic Period from fossil data. Then they take a medium sized sauropod like Apatosaurus louise, which weighed around 20,000kg, as a representative animal. Finally they apply a relationship which gives an indication of methane production per animal, while being careful to note the relatively shorter Mesozoic day:
Methane (litres per day) = 0.18 (body mass in kg) 0.97
Multiplying it all out and the bottom line is that these beasts could put out 520 million tonnes of methane per year into the atmosphere. Incredibly, this is comparable to modern day emissions when the effects of this are apparent to all.The upshot the authors draw is that sauropods were drivers of climate change during the Mesozoic Era. There are some uncertainties in the paper to be sure. For one, the metabolism of dinosaurs is still an unknown and this has implications for their output. But the argument seems to be a sound one and this was all achieved with some fairly basic maths.
References
1. Ruxton, GD, Houston, DC (2002). Modelling the energy budget of a colonial bird of prey, the Ruppell’s griffon vulture, and consequences for its breeding ecology. African Journal of Ecology. 40 (3) p. 260–266.
“Dinosaurs have become boring. They’re a cliché. They’re overexposed” – Stephen Jay Gould
