The Great London [Search results for Rainforests] 

Scientists from Wageningen UR and other institutes are proposing a new research model - the turnover model - as a way of answering the question why there are always so many plant species in tropical rainforests.

In their publication in New Phytologist magazine, the Dutch, British and Swiss scientists show that major evolutionary changes, such as the origin of large groups of species, occur with a reasonably constant frequency while the origin of new species is an explosive process.

Various models

Darwin’s contemporary Alfred Russel Wallace already argued that the Tropics are, in essence, a museum of biodiversity. As tropical climates are stable, Wallace suggested that species would gradually increase in number over longer time periods, the so-called museum model. More recently, however, it was suggested that the Pleistocene ice ages, and the impact thereof on the climate in the Tropics, resulted in recent explosions of speciation, the so-called cradle model.

Both models are supported by previous research into patterns of diversification in tropical plants. This research is performed by means of reconstructed ‘phylogenetic trees’; genealogical trees that show the interrelated  descent of plant species. Where analyses of plant families focused on studying as many evolutionary lines as possible from the family, diversity was shown to increase gradually. For instance, the development of diversity in important tropical plant groups such as palm trees, the leguminous family and the soursop family, appear to follow the museum model. However, within these large plant families there are also plant genera that seem to follow the cradle model: so-called radiations in which many different species developed recently and over a short period of time.

Equatiing seems impossible

Equating these two models seems an impossible task. How can a large plant family that presents an explosive increase in the number of species diversify as an entire family following the museum model? The answer lies in analysing more species per family, and better modelling speciation over long periods in evolution via the computer.

Mahogany trees

Scientists from Wageningen UR, Kew (London) and Zürich compiled the largest amount of data so far for the Meliaceae , or mahogany family. This family mainly grows in the Tropics, and is known for valuable wood such as mahogany and Spanish cedar. Parts of the nuclear and chloroplast genome of approximately 35% of the species were sequenced; a technology in which all the building blocks of the DNA are mapped.

The analysis of evolutionary diversification showed that the diversity of larger groups, such as plant genera and families, does develop in accordance with the museum model, i.e., with a certain constant frequency in the origin of new branches. The scientists showed that, in addition to this ‘museum fundament’, the origin of individual species is an explosive process which occurs in accordance with the cradle model.

‘Young’ species

The research shows that the mahogany family developed approximately 68 million years ago. The circa 200 mahogany species that grow in the South American rainforests are largely the result of two explosions in speciation (radiations) that occurred independently in two evolutionary lines in the late Miocene epoch, which was less than 10 million years ago.

An interesting aspect of this explosive origin of large numbers of species within the mahogany family is that it involves two different groups within the family which independently evolved the same ecological adaptations, such as plant height and an adaptation of seeds to the same animal species that distribute them. In addition, the two groups show a similar speed of speciation. These abrupt increases in speciation speed occurred after the mahogany family had left its original habitat (tropical dry forests and seasonal forests) and colonised the rainforests, where they were faced with different climate conditions.

New model for evolution

The results of the study show that most mahogany species in the Tropics are relatively recent. It can be assumed that this also applies to other families. The authors propose a new model, the turnover model, in which the number of evolutionary lines increases with a more or less constant speed, while speciation occurs separately and in a more explosive way.

Source: Wageningen University [June 19, 2015]

Research reveals that large areas of 'degraded' forest in Southeast Asia can play an important role in conserving mammal diversity.

Mammals can be one of the hardest-hit groups by habitat loss, and a lot of research has been carried out to find the best ways to conserve mammal diversity.

Much of this research has focused on very large-scale changes in land use and the impacts this will have on overall mammal diversity. However, many important decisions about land use are made at much more local scales, for example at the level of individual landowners.

Now, in a detailed study led by Imperial College London that looked at mammal diversity across different small-scale landscapes in Borneo, researchers have identified previously logged forests as an overlooked source of refuge for mammals.

These 'selectively logged' forests, where only certain tree species are removed, are often considered to be degraded and are frequently cleared to make way for plantations. The new results, published in the >journal Ecological Applications, suggest they should be better protected.

The team recorded mammals using trap-and-release techniques and motion-sensing cameras over three years, creating an unprecedented 20,000 records of species in three land-use types: old-growth forest, logged forest and oil palm plantation. This is one of the most intensive studies of rainforest mammal diversity ever undertaken.

To their surprise, they found that mammal diversity for large mammals, like the clouded leopard and civets, was similar for both old-growth forests and logged forests. For small mammals, such as squirrels and rodents, the diversity was actually higher in logged forests.

Both sizes of mammals however suffered heavy losses of diversity in oil palm plantations. Most species discovered on the plantations likely spilled over from adjoining forests or riparian zones -- strips of forests surrounding rivers to reduce the chance of flooding.

Lead researcher Dr Oliver Wearn, who completed the research for his PhD in the Department of Life Sciences at Imperial, said that the surprise result that mammal diversity remains high in logged forests may be because of the way habitats are distributed.

"The logging process creates a greater variation in habitat types in a smaller area, from untouched areas on steep slopes to completely denuded areas of open grassland. Old-growth forests would likely have the same diversity if we looked at them on a much larger scale."

Dr Wearn also stresses that while a greater diversity is recorded now in these logged forests, it cannot yet be certain that this diversity will remain in the future as the knock-on effects of habitat loss take effect on mammals and other rainforest species.

He added: "What we can say from this study is that protecting those large areas of forest that have already been logged could help conserve mammal species better than preserving fragmented pockets of forests inside oil palm landscapes."

This study complements another recent study from Imperial, where researchers recommended rehabilitating logged forests as a way to prevent highly threatened species from becoming extinct.

"Where old growth forests remain, however, these are still the best habitats for mammals and other native species, and should be the absolute top priority for conservation," said Dr Wearn.

Author: Hayley Dunning | Source: Imperial College London [August 22, 2016]

When members of the BaYaka Pygmies living in the northern Republic of Congo get sick, they don't just go to the doctor for a prescription. Instead, they rely on their shared knowledge of medicinal plants to help them get well. Now, researchers reporting in the Cell Press >journal Current Biology on September 8 have examined shared uses of those plants to understand how Pygmies have passed their extensive plant knowledge along from one person to the next.

The findings show the important role of marital bonds in passing information to otherwise distant families. There were some surprises, too.

"I wasn't expecting that plant uses would be so diverse," says Gul Deniz Salali (@DenizSalali) of University College London. She hadn't expected to find that plants would play an important role in executing social norms, either. "But many Pygmies told me that they used particular plants to detect and punish cheaters."

Salali was interested in exploring how hunter-gatherers accumulated the vast repertoire of plant uses that have helped them to survive in tropical rainforests. To find out, she and her colleagues examined the reported co-occurrence of plant uses between pairs of BaYaka Pygmy individuals based on extensively conducted interviews. Their study included reported uses of 33 different plants by 219 individuals living in four camps.

"We found that long-term pair bonds between men and women allowed otherwise distant families to combine information on medicinal uses of plants," Salali says. "Living in multi-family camps, on the other hand, enabled Pygmies to exchange and accumulate plant knowledge related to cooperative foraging and social beliefs."

The most commonly reported medicinal uses of plants were for treating digestive and respiratory disorders. The BaYaka also use some plants for collecting caterpillars or honey and as a poison for killing monkeys or fish. Other plants were used to regulate social life, including matters concerning lying or sexual taboos.

As an example, Salali says, some Pygmies use the juice extracted from a particular type of tree bark to detect and punish cheaters. "If someone cheated their partner, camp members would squeeze the poisonous juice into the person's eyes which could affect his or her vision. If his or her vision was affected, then people thought the person was guilty. I found that the knowledge on this type of plant use was widely shared among the campmates."

Knowledge of medicinal plants is mainly shared between spouses and other relatives, they found. But plant uses associated with foraging and social norms were often shared more widely among campmates, regardless of relatedness, playing an important role in camp-wide activities that require cooperation.

The researchers also found that BaYaka mothers who used more plants for treating certain diseases had healthier children.

Salali says her next step is to compare plant knowledge and use in hunter-gatherers living in varying proximity to market towns in Congo. "I have lived in some Pygmy camps that were located in the forest, and some larger ones that were located in a logging town," she says. "I am interested in exploring the biological and cultural adaptations of groups in transition from a nomadic hunter-gatherer lifestyle to a more sedentary farming way of life."

Source: Cell Press [September 08, 2016]

Researchers from Royal Holloway, Birkbeck and Kings College, University of London used satellite images to map abandoned shore lines around Palaeolake Mega-Chad, and analysed sediments to calculate the age of these shore lines, producing a lake level history spanning the last 15,000 years.

At its peak around 6,000 years ago, Palaeolake Mega-Chad was the largest freshwater lake on Earth, with an area of 360,000 km2. Now today's Lake Chad is reduced to a fraction of that size, at only 355 km2. The drying of Lake Mega-Chad reveals a story of dramatic climate change in the southern Sahara, with a rapid change from a giant lake to desert dunes and dust, due to changes in rainfall from the West African Monsoon. The research, published in the journal Proceedings of the National Academy of Sciences confirms earlier suggestions that the climate change was abrupt, with the southern Sahara drying in just a few hundred years.

Part of the Palaeolake Mega-Chad basin that has dried completely is the Bodele depression, which lies in remote northern Chad. The Bodele depression is the World's single greatest source of atmospheric dust, with dust being blown across the Atlantic to South America, where it is believed to be helping to maintain the fertility of tropical rainforests. However, the University of London team's research shows that a small lake persisted in the Bodele depression until about 1,000 years ago. This lake covered the parts of the Bodele depression which currently produce most dust, limiting the dust potential until recent times.

"The Amazon tropical forest is like a giant hanging basket," explains Dr Simon Armitage from the Department of Geography at Royal Holloway. "In a hanging basket, daily watering quickly washes soluble nutrients out of the soil, and these need to be replaced using fertiliser if the plants are to survive. Similarly, heavy washout of soluble minerals from the Amazon basin means that an external source of nutrients must be maintaining soil fertility. As the World's most vigorous dust source, the Bodele depression has often been cited as a likely source of these nutrients, but our findings indicate that this can only be true for the last 1,000 years," he added.

Source: University of Royal Holloway London [June 29, 2015]

The forests of Central Africa could be home to up to 920,000 Pygmies, according to researchers from UCL, Manchester Metropolitan University and the University of Malaga, who have conducted the first measured estimate of the population and distribution of these indigenous groups.

Up until now it has not been possible to determine the numbers and actual geographic ranges of Pygmy communities, because of their location in remote forest areas, mobility, lack of census data, and imprecise and partial sources of information. Pygmy communities live in rainforests across nine countries in Central Africa—an area of some 178 million hectares—where they make up a very small minority of the total population.

Despite the Pygmies' significance to humanity's cultural diversity as the largest group of active hunter-gatherers in the world, the new study, published in >PLOS ONE, is the first to predict how many Pygmies are likely to be found in the vast expanse of tropical forests in Central Africa. The study maps their distribution and identifies which areas are of ecological importance.

Dr Jerome Lewis (Hunter-Gatherer Resilience Project, UCL Anthropology), co-author of the paper, said: "This is a very underprivileged and neglected group of people many of whom have already lost their forest land, livelihoods and whose rich cultural traditions are seriously threatened in many regions.

"Information on their locations and population numbers are crucial for developing appropriate human rights, cultural and land security safeguards for them, as for other indigenous peoples."

Using a compilation of evidence collected by an unprecedented number of researchers, the authors generated the largest database of Pygmy camp locations throughout their known range.

As there are no known accurate censuses of Pygmy population the researchers used a statistical method, developed by paper co-author Dr Jesus Olivero (University of Malaga), to forecast the distribution of Pygmies in Central Africa. Based on species distribution models that investigate the relationship between environmental conditions and the distribution of organisms, the study is the first to apply this method to human societies and their cultural diversity.

Dr Olivero said: "By using tried and tested animal and plant distribution models we hope to promote a greater awareness of the importance of these too often ignored and marginalized groups in this region."

Professor John Fa (Manchester Metropolitan University), co-author, explained that understanding where and how Pygmy communities live is an important first step in supporting them and safeguarding their rights.

"It's important for all of the countries involved to come together to help support Pygmies' cultures and human rights to make sure they are respected and understood.

"At the end of the day, 900,000 people living in small groups in such a vast area can very easily be ignored, leading to their cultural extinction, and given the extraordinary role they have played in the human story since well before antiquity, we don't want that."

Source: University College London [January 15, 2016]

The first annual State of the World's Plants report, which involved more than 80 scientists and took a year to produce, is a baseline assessment of current knowledge on the diversity of plants on earth, the global threats these plants currently face, as well as the policies in place and their effectiveness in dealing with threats.

"This is the first ever global assessment on the state of the world's plants. We already have a 'State of the World's ...birds, sea-turtles, forests, cities, mothers, fathers, children even antibiotics' but not plants. I find this remarkable given the importance of plants to all of our lives- from food, medicines, clothing, building materials and biofuels, to climate regulation. This report therefore provides the first step in filling this critical knowledge gap." said Professor Kathy Willis, Director of Science at the Royal Botanic Gardens, Kew at the report launch on Monday.

"But to have effect, the findings must serve to galvanise the international scientific, conservation, business and governmental communities to work together to fill the knowledge gaps we've highlighted and expand international collaboration, partnerships and frameworks for plant conservation and use," she added.

The status of plants outlined in the report is based on the most up to date knowledge from around the world as of 2016 and is divided into three sections; describing the world's plants, global threats to plants and policies and international trade.

Naming and Counting

The first section focuses on the diversity of plants on earth, noting that there are now an estimated 391,000 vascular plants known to science of which 369,000 are flowering plants -- with around 2,000 new vascular plant species described annually. Some of the most exciting were found during fieldwork while many others were detected only after they have already been preserved and filed as herbarium specimens and a few have been discovered in the glasshouses at Kew.

One of the largest carnivorous plants known (1.5m in height), a new insect-eating plant of the sundew genus called Drosera magnifica was even first discovered on Facebook. Eighteen new species of the genus Ipomoea in the morning glory family, were described from Bolivia last year, among them a close relative of the sweet potato, Ipomoea batatas, offering exciting options for the future of this crop.

"But there are still large parts of the world where very little is known about plants. Identification of these important plant areas is now critical." said Steve Bachman, strategic output leader for the State of the World´s Plants report, RBG Kew. "Similarly, we still only know a fraction of the genetic diversity of plants and whole-genome sequences are currently available for just 139 species of vascular plants. Activity in this area needs to speed up," he added.

Useful plants

In terms of the uses of plants, the report collates data from multiple data sources to reveal that at least 31,000 plant species have a documented use for medicines, food, materials and so on. The majority (17,810 plants) of those now documented have a medicinal use.

Aside from the plants that are currently in use, the report looks at where collection efforts should focus to include plants that will be useful in the future. One set of plant species of critical importance to global food security are the wild relatives of crops, a pool of genetic variation that can help to drive the improvement of our crops into the future. A recent inventory has revealed that there are currently 3,546 prioritised global plant taxa identified as 'crop wild relatives' and Kew's Millennium Seed Bank (MSB) includes 688 crop wild relatives among its over 78,000 accessions, but there are still substantial gaps.

Research in this sector has found that the traits that have been bred into crops over years of domestication are not necessarily the same ones that will provide the greatest climate resilience. Given that many of the wild populations of these species are under considerable threat due to land-use and climate change there is an urgent need to conserve those species not adequately represented in current collections. More seed banking will help preserve a wider range of alternatives to the crops on which the world over relies today (report pages 20-23).

Climate change

The report also explores current knowledge around the impact of climate change on plants and finds that while there is a good understanding for some regions of the world, there are still large areas for which little or no research exists. In those areas where good data is available, clear impacts are visible, including changes in flowering times, turnover in plant communities and movement of species with changing climates.

Research referenced in the report shows that all but one of the world's biomes have experienced more than 10% change in land-cover type in the past decade due to the combined impacts of land-use and climate change.

This research, led by teams at the International Center for Tropical Agriculture in Colombia is also the first of its kind to allocate timeframes for the changes in policy and practice needed to maintain food production and security in Africa. It identifies that up to 30% of areas growing maize and bananas, and up to 60% of those growing beans, are likely to become unviable by the end of the century. But it also highlights some crops like cassava and yams that are showing much greater resilience and could worth focusing on in years to come (report pages 36-39).

"Having proof that root crops like cassava and yams are among the climate-smart crops of the future for sub Saharan Africa is vital for informing policy and planning today," added Professor Willis.

Further research into building a climate resilient coffee economy in Ethiopia published in this report highlights how coffee production is likely to be drastically affected by climate change, but claims that this could be offset if there were interventions now to develop new areas for coffee plantations, which may even lead to gains in coffee production.

Important plant areas

1,771 important plant areas have been identified globally but very few currently have conservation protection. In the UK alone, 165 such sites have been recognised, including parts of the Atlantic woodlands and the Celtic rainforests which are considered to be globally important. These sites include the Lizard in Cornwall, the Brecklands in East Anglia and parts of the west coast of Scotland. Important plant areas have also been identified in several of the UK Overseas Territories including the Falkland Islands and plans are underway to extend this programme to the Caribbean UK Overseas Territories.

Invasive species

A large movement of invasive alien plant species is also occurring. Nearly 5000 plant species are now documented as invasive in global surveys. These plants are causing large declines in native plants, damaging natural ecosystems, transforming land-cover and often causing huge economic losses. In the UK, this includes the highly invasive Japanese knotweed (Reynoutria japonica), introduced as an ornamental plant to Britain in the mid-19th century and costing Great Britain more than £165 million annually to control (report pages 48-51).

The report calls for closer collaboration between institutions and organisations working with invasive species to enable the establishment of a single global list that documents taxonomy, threat, distribution, control and other relevant information. Stricter enforcement of legislation and increased implementation of quarantine procedures would minimise the risk of further.

Plant diseases

There are many emerging threats also occurring with plant diseases, and research effort into these diseases is skewed towards countries with a wealthier research infrastructure.

Threats and extinction

Best estimates lead us to believe that 21% of the world's plants are currently threatened with extinction and ongoing monitoring will allow us to determine whether the trend is of plants slipping closer towards extinction or becoming less threatened.

Plants and policies

Although trade in plants supports livelihoods worldwide, illegal or unsustainable trade is causing additional pressure on wild biodiversity and strict enforcement of international legislation is crucial. Adoption and implementation of policies such as CITES (Convention on International Trade in Endangered Species) have had demonstrable benefits and there is cause for optimism that the Nagoya Protocol will enhance the effectiveness with which countries conserve and utilise their biodiversity.

One of the main plant groups that are still widely traded are orchids, a fact confirmed by data from the UK borderforce. Of all plants plants seized at Heathrow airport in 2015 over 42% were wild orchids.

"This is the most significant horizon-scanning document to be released by Kew in recent decades and I hope as many people as possible will access the findings," said Richard Deverell, Director of the Royal Botanic Gardens, Kew.

"Plants represent one of the most important constituents of biodiversity, the foundation of most of the world's ecosystems and hold the potential to tackle many of the world's present and future challenges. We are uniquely placed to unlock their importance and are proud to have both the catalogue of over 250 years of collections and active scientific field work globally that allows us to interpret the data so it will have multiple uses for generations to come," he added.

Read the report >here.

Source: Royal Botanic Gardens Kew [May 11, 2016]