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Gijsbert Werner, Postdoctoral Fellow and Stuart West, Professor of Evolutionary Biology, both in the Department of Zoology, explain the process of plant cooperation, in relation to their new study published in PNAS, which has shed light on why cooperative relationships breakdown.

Unseen to most of us, almost all plants form below-ground interactions with beneficial soil microbes. One of the most important of these partnerships is an interaction between plant roots and a type of soil fungi called arbuscular mycorrhizal fungi.

The fungi form a network in the soil and provide the plant with soil minerals, such as phosphorus and nitrogen. In return, the fungi receive sugars from the plant. This cooperation between plants and fungi is crucial for plant growth, including of many crops. Plants sometimes even get up to 90% of their phosphorus from these soil fungi.

In collaboration with a team of international researchers, we set out to better understand plant cooperation. We wanted to know why some relationships of plants with soil fungi flourish and others collapse.

This involved analysing a large database of plant-fungal interactions containing thousands of species and using computer models to reconstruct the evolutionary history of the partnership. We found that despite having successfully cooperated for over 350 million of years, partnerships among plants and soil fungi can break down completely.

Once we knew that that plant-fungus cooperation could fail, we wanted to understand how and why the relationship breaks down. We found that in most cases the plants were replacing the fungi with another cooperative partner who did the same job, either different fungi or bacteria. In the other cases, plants had evolved an entirely different way of obtaining the required minerals – for instance, they had become carnivorous plants which trap and eat insects.

Our study shows that despite the great potential benefits of the relationship, cooperation between plants and fungi has been lost about 25 times. It is quite crazy that such an important and ancient collaboration has been abandoned so many times. So why did this happen?

One explanation is that in in some environments, other partners or strategies are a more efficient sources of nitrogen or phosphorus, driving a breakdown of previously successful cooperation between plants and fungi.

For instance, carnivorous plants are often found in very nutrient-poor bogs. Even an ancient beneficial fungus, specialised in efficiently shuttling nutrients to their partner plants simply cannot get the job done there. So, plants evolve a different way to get their nutrients: trapping insects.

A next step is to now find out in what conditions the various different nutrient strategies are found? Where on our planet do plants keep their original fungi? Where do they go for another solution to get their nutrients? Other work focuses on the potential that some fungi evolve to become ‘cheaters’ - taking the benefit from the partnership but no longer contributing to it and ultimately driving its breakdown.

Uranus

This blog post is adapted from an article published by the Gemini Observatory.

Even after decades of observations, and a visit by the Voyager 2 spacecraft, Uranus held on to one critical secret: the composition of its clouds. Now, one of the key components has finally been verified.

Professor Patrick Irwin from the University of Oxford's Department of Physics and global collaborators spectroscopically dissected the infrared light from Uranus captured by the eight-meter Gemini North telescope on Hawaii's Maunakea. They found hydrogen sulfide, the odiferous gas that most people avoid, in Uranus’s cloud tops. The long-sought evidence is published in the journal Nature Astronomy.

The Gemini data, obtained with the Near-Infrared Integral Field Spectrometer (NIFS), sampled reflected sunlight from a region immediately above the main visible cloud layer in Uranus's atmosphere. Professor Irwin said: 'While the lines we were trying to detect were just barely there, we were able to detect them unambiguously thanks to the sensitivity of NIFS on Gemini, combined with the exquisite conditions on Maunakea. Although we knew these lines would be at the edge of detection, I decided to have a crack at looking for them in the Gemini data we had acquired.'

Dr Chris Davis of the United States' National Science Foundation, a funder of the Gemini telescope, said: 'This work is a strikingly innovative use of an instrument originally designed to study the explosive environments around huge black holes at the centres of distant galaxies. To use NIFS to solve a longstanding mystery in our own solar system is a powerful extension of its use.'

Astronomers have long debated the composition of Uranus’s clouds and whether hydrogen sulfide or ammonia dominates the cloud deck, but lacked definitive evidence either way. Professor Irwin said: 'Now, thanks to improved hydrogen sulfide absorption-line data and the wonderful Gemini spectra, we have the fingerprint which caught the culprit.' The spectroscopic absorption lines (where the gas absorbs some of the infrared light from reflected sunlight) are especially weak and challenging to detect, according to Professor Irwin.

The detection of hydrogen sulfide high in Uranus's cloud deck (and presumably Neptune’s) contrasts sharply with the inner gas giant planets, Jupiter and Saturn, where no hydrogen sulfide is seen above the clouds, but instead ammonia is observed. The bulk of Jupiter and Saturn's upper clouds are comprised of ammonia ice, but it seems this is not the case for Uranus. These differences in atmospheric composition shed light on questions about the planets' formation and history.

Dr Leigh Fletcher, a member of the research team from the University of Leicester, adds that the differences between the cloud decks of the gas giants (Jupiter and Saturn), and the ice giants (Uranus and Neptune), were likely imprinted way back during the birth of these worlds. He said: 'During our solar system’s formation, the balance between nitrogen and sulphur – and hence ammonia and Uranus's newly detected hydrogen sulphide – was determined by the temperature and location of planet's formation.'

Another factor in the early formation of Uranus is the strong evidence that our solar system's giant planets likely migrated from where they initially formed. Therefore, confirming this composition information is invaluable in understanding Uranus's birthplace, evolution and refining models of planetary migrations.

According to Dr Fletcher, when a cloud deck forms by condensation, it locks away the cloud-forming gas in a deep internal reservoir, hidden away beneath the levels that we can usually see with our telescopes. He said: 'Only a tiny amount remains above the clouds as a saturated vapour. And this is why it is so challenging to capture the signatures of ammonia and hydrogen sulfide above cloud decks of Uranus. The superior capabilities of Gemini finally gave us that lucky break.'

Dr Glenn Orton of NASA's Jet Propulsion Laboratory, another member of the research team, said: 'We've strongly suspected that hydrogen sulfide gas was influencing the millimetre and radio spectrum of Uranus for some time, but we were unable to attribute the absorption needed to identify it positively. Now, that part of the puzzle is falling into place as well.'

While the results set a lower limit to the amount of hydrogen sulfide around Uranus, it is interesting to speculate what the effects would be on humans even at these concentrations. Professor Irwin said: 'If an unfortunate human were ever to descend through Uranus's clouds, they would be met with very unpleasant and odiferous conditions. However, suffocation and exposure in the -200C atmosphere made of mostly hydrogen, helium and methane would take its toll long before the smell.'

The new findings indicate that although the atmosphere might be unpleasant for humans, this far-flung world is fertile ground for probing the early history of our solar system and perhaps understanding the physical conditions on other large, icy worlds orbiting the stars beyond our Sun.

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In a study of 11 different plant species, published in Molecular Biology and Evolution, researchers at the University of Oxford have shown that the speed at which plants evolve is linked to how good they are at photosynthesis.

The team from the Oxford Department of Plant Sciences detected differences in plant gene evolution that could be attributed to how good or bad those plants were at photosynthesis.

Plants need nitrogen to do photosynthesis. They use it to build the proteins they need to turn atmospheric CO2 into sugars. However, plants also need nitrogen to build their genes, and the different letters in DNA cost different amount of nitrogen to make - A and G are expensive while C and T are cheaper. What the study found is that plants that invest lots of nitrogen in photosynthesis use cheaper letters to build their genes. This molecular “penny-pinching” restrains the rate at which genes evolve and so plants that spend a lot of nitrogen on photosynthesis evolve more slowly.

The study provides a novel link between photosynthesis and plant evolution that can help explain why the number of plant species is unevenly distributed across the globe. It also helps to explain why plants that are highly efficient at photosynthesis form new species faster than plants with lower efficiency.

Lead author, Dr Steven Kelly, from Oxford’s Department of Plant Sciences, said: 'These results also allow us to make predictions about how plants evolve in response to a changing climate. For example, when atmospheric CO2 concentration goes up, plants don’t need to invest as much nitrogen in trying to capture it, and so more of the nitrogen budget in the cell can be spent on making genes. That means when atmospheric CO2 concentration goes up plant genes evolve faster.’

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Is it possible to use natural resources effectively and protect the Earth's wildlife and biodiversity? Oxford University scientists have proposed a new framework that could achieve exactly that. William Arlidge, a doctoral student and Professor EJ Milner-Gulland, Tasso Leventis Professor of Biodiversity; Director, Interdisciplinary Centre for Conservation Science; Fellow of Merton College, discuss their new research as featured in BioScience.

In an effort to help answer one of the biggest questions in conservation,  in our new paper we discuss whether a framework used to reduce negative impacts from development on biodiversity could be expanded to account for all human impacts on nature. 

Biodiversity is the variety of life in all its forms on planet Earth. It’s a broad concept, and conserving it is complex as it needs multifaceted approaches that are aimed at understanding what is most valuable, and at most risk, and what are the best approaches to undertake conservation that is not at odds with other societal needs. Our current efforts to do so comprise a patchwork of international goals, national plans, and local interventions. While our conservation efforts are not without great successes, overall, they are failing to achieve all their desired outcomes. This is largely down to us, because human needs for ever-more space to grow food, harvest wild products like timber and fish, and build infrastructure, are squeezing out nature.

Our continued use of biodiversity to improve our wellbeing is, sadly, all too often in conflict with our efforts to conserve it. At the broadest scale the United Nations Sustainable Development Goals provide a global vision to conserve and sustainably use biodiversity, however guidance on how this broad vision translates to actions at national, regional, and local levels is not clear.

In our new publication, we propose taking a more systematic approach to achieving biodiversity conservation goals, by accounting for all human biodiversity impacts and conservation efforts within a unified global framework.

This framework expands on an existing concept known as the ‘mitigation hierarchy’, which offers a balanced and systematic way to account for and mitigate harmful impacts to biodiversity, while still allowing development activities to occur.

The mitigation hierarchy works by first trying to predict all the negative impacts that are likely to occur as part of a given activity. Creating a palm oil plantation, for example, will mean directly losing some tropical forested areas and their associated biodiversity. There will also be other more indirect impacts such as the risk of sedimentation, pollution and noise disturbance. To account for all these different impacts, sequential steps are taken: developers need first to consider the extent to which they can avoid causing damage. Then they need to minimise the damage they cause from their operations. Next, they should remediate any temporary damage. All these steps mitigate biodiversity impacts on site. Following the implementation of these steps, any residual impacts to biodiversity not mitigated must be offset by boosting biodiversity elsewhere.

Avoiding impacts could include selecting sites that have no biodiversity impact or foregoing the development effort all together. Minimisation could include restricting heavy machinery used to remove palm oil to particular roadways and halting construction during sensitive times. Remediation could include reinstating roads to their previous condition once they are finished with. Offsetting might include replanting forest habitat elsewhere. The logic in undertaking these steps is to achieve a neutral or positive level of impact to biodiversity after a given damaging activity (often referred to as ‘No Net Loss’ or a ‘Net Gain’ of biodiversity).

While the theoretical and practical challenges in achieving No Net Loss of biodiversity are becoming increasingly well described and reported (see papers from Joe Bull, Martine Maron, and David Lindenmayer), the underlying concept of the mitigation hierarchy is both powerful and much more widely applicable than has so far been appreciated.

Currently there is a widespread and piecemeal project-level approach to achieving No Net Loss of biodiversity taking place. This means that, if biodiversity gains and losses were to be aggregated, biodiversity could be lost even if individual projects appear to be reaching their targets. If the concept is to truly have biodiversity benefits, there is a need for a multi-scale approach to No Net Loss, so that wider goals are not contradicted by project-level use of the mitigation hierarchy.

In our publication we propose the use of the mitigation hierarchy to navigate the conservation-development trade-off at the broadest scale possible, the whole planet. Incorporating all human impacts on biodiversity within the single standardised paradigm with a broad biodiversity conservation goal. Crucially, a global mitigation hierarchy offers a systematic framework that is both scalable from the project to the national and international levels, as well as being standardised between the conservation sectors of sustainable use (e.g., certification schemes), minimising the impact of development (e.g., No Net Loss), and efforts to directly restore or protect sites (e.g., protected areas).

Conserving biodiversity while simultaneously seeking to use it for humanity's needs is a huge challenge, which some suggest is not possible on our current growth trajectory. Others have called for half the planet to be set aside for biodiversity conservation, or for more space to be given to nature. But in the absence of a clear pathway to achieving it, it is difficult to see how these aspirations can translate into real biodiversity gains. Our approach cannot solve all of these challenges, but what the mitigation hierarchy offers is transparency, enabling clear understanding of what the consequences of various uses of nature are, with flexibility to address a variety of human impacts on biodiversity, across different sectors and scales.

Fundamental changes are needed if humanity is to reverse the current biodiversity crisis and put the planet on a sustainable course for the future. However, these changes will only be possible if we can see a way forward. Quantifying and accounting for all human-caused impacts to biodiversity could help humanity to reduce these impacts in a feasible and equitable way. A global mitigation hierarchy could be the first step towards achieving such a vision.

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Dr Molly Grace, NERC Knowledge Exchange Fellow in the Oxford University Department of Zoology, discusses the potential impact of IUCN Green Species List, a framework for a standard way of measuring conservation success. A project that she and the team at the Interdisciplinary Centre for Conservation Science played a key role in developing.

What is the goal of species conservation? Many would say that it is to prevent extinctions. However, while this is a necessary first step, conservationists have long recognized that it should not be the end goal. Once a species is stabilised, we can then turn our attention to the business of recovery - trying to restore species as functional parts of the ecosystems from which humans have displaced them. However, to do this, there must be a rigorous and objective way to measure recovery. 

Imagine this scenario: A species is teetering on the brink of extinction. In fact, it has been classified on the IUCN Red List of Threatened Species (the global standard for measuring extinction risk) as Critically Endangered. You rally a global team of scientists, conservation planners, and land managers to put their heads together and figure out how to save this species. This team works relentlessly to bring this species back from the edge, and little by little, the species improves. After years, or even decades, of work, the team achieves its goal— the species is no longer considered threatened with a risk of extinction! However, no one is celebrating—in fact, the mood has become decidedly sombre.

There is a simple reason for this apparent paradox, due to limited conservation budgets, species which are classified as being at risk of extinction are preferentially awarded funding. While this makes sense at a wide scale - of course we should be working hardest to save the species which face an imminent risk of vanishing from the planet - it poses a problem for species who have benefited from concerted conservation actions and are no longer in the “danger zone.” Once the threatened classification vanishes, often so does funding. Without continued protections, species may slip back into the threatened category, nullifying the effect of decades of work. Thus, there is a perverse incentive to stay in the exclusive “highly endangered” club - at least on paper. But this prevents us from celebrating the huge difference that conservation can make.

With the creation of the IUCN Green List of Species, we hope to reverse this perverse incentive to downplay conservation success. The Green List, still in development, will assess species recovery and how conservation actions have contributed to species recovery. It will also calculate the dependence of the species on continued conservation, by estimating what would happen if these efforts stopped. This can be used as an argument for continued conservation funding. With the Green List working in tandem, we can stop thinking of Red List “downlisting”— moving from a high category of extinction risk, to a lower one—as a demotion which disincentivises funding, but rather see it for what it truly is: a promotion which should be celebrated. The framework would be applicable across all forms of life on the planet: aquatic and terrestrial species, plant, animal, and fungal species, narrow endemics to wide-ranging species, you name it.

In our recent paper, we presented this framework, which will potentially measure recovery and work in tandem with the assessment of extinction risk (IUCN Red List) to tell the story of a species. For example, a species that is in no danger of disappearing from the planet (Red List assessment) might nonetheless be absent from many parts of the world in which it was previously found, and so cannot be considered fully recovered (Green List assessment). The local loss of a species can have cascading effects on the rest of the ecosystem.

The Green List of Species also assesses the impact that conservation efforts have had, and could have in the future. For example, the charismatic saiga antelope (Saiga tartarica), found throughout Central Asia, is currently considered “Critically Endangered” on the Red List. However, our Green List assessment shows that in the absence of past conservation efforts, many more populations would be extinct or in worse shape today. We also show that with continued conservation, the saiga's future prospects are bright—a low risk of extinction, reestablishment of populations where they are locally extinct, and some functional populations.

We hope that the Green List of Species will help to encourage and incentivise more ambitious conservation goals, moving beyond triage at the edge of extinction.

If the Green List sparks optimism within you and you’d like to get involved in the process, you can learn more here