#PlantDiversity; #Europe, #PlantSpecies; #TemperateForests; #NatureEcology; #Evolution
Germany (Europe) Apr 14 (Canadian-Media): In Europe's temperate forests, less common plant species are being replaced by more widespread species. An international team of researchers led by the German Centre for Integrative Biodiversity Research (iDiv) and the Martin Luther University Halle-Wittenberg (MLU) has found that this development could be related to an increased nitrogen deposition. Their results have been published in the journal Nature Ecology & Evolution, phys.org/news reports said.
The researchers analysed data from a total of 68 different sites in temperate forests across Europe. Image Credit: Nature Ecology and Evolution
In Europe's temperate forests, less common plant species are being replaced by more widespread species. An international team of researchers led by the German Centre for Integrative Biodiversity Research (iDiv) and the Martin Luther University Halle-Wittenberg (MLU) has found that this development could be related to an increased nitrogen deposition. Their results have been published in the journal Nature Ecology & Evolution.
The number of animal and plant species is declining globally. By contrast, there are occasionally opposing trends in individual local ecosystems, where there may even be evidence of an increase in species richness (number of species). How can this apparent contradiction be explained, and what are the reasons for it?
It was precisely these questions that an international team of scientists wanted to explore. Using data from a total of 68 different locations in temperate forests in Europe—including forest sites in Thuringia, Saxony-Anhalt and Bavaria—they investigated how the diversity of herb-layer plant species has changed over the past decades. For this, the researchers had to assess stocks of 1,162 different plant species. This set of data was compiled by a network of forest ecologists, called forestREplot. "This network has the advantage that the experts on the actual locations can be asked if something is unclear, and, in this way, it differs from many other large databases," said lead author Ingmar Staude, a doctoral student at iDiv and the MLU.
The analysis of these data was made possible by the sDiv synthesis centre of iDiv. The scientists found that plant species with a small geographical range, which can often be found in only a few forests, tend to have an increased risk of extinction within the respective forests. "This is not so much due to the smaller population size of such plants, but rather to their ecological niche," explains Ingmar Staude. Small-ranged species are often those adapted to relatively few nutrients in the soil.
The scientists were able to show that chronic and excessive nitrogen deposition in many parts of Europe is related to the increased risk of extinction of such species. In contrast, plant species that prefer nutrient-rich soils, such as nettle and blackberry benefit. These plants grow faster under higher nutrient supply and have now a sudden competitive advantage.
While small-ranged species have disappeared, widespread, nitrogen-loving, and occasionally exotic species are on the rise. The average biodiversity of individual forests has therefore not actually decreased. However, the biodiversity of the biome has decreased as small-ranged species were commonly lost. Based on their research, the researchers estimated a 4% decrease over the last decades. However, they point out that many of the sites investigated are in protected areas, and if areas used for forestry were to be examined, the decline could be even greater.
"We now have to find out whether the processes we observe in forests are similar in other biomes," said Ingmar Staude. With the help of the sDiv synthesis centre of iDiv, data are to be evaluated now for a number of biomes; for example, European grasslands and Alpine ecosystems.
The loss of less common species has an impact on ecosystems. If individual plant species disappear, some insect species and soil organisms also disappear along with them. And the further regional floras homogenise, the less effectively these ecosystems can react to changing environmental conditions. The scientists of this study argue that nitrogen deposition needs to be reduced to decrease the extinctions of small-ranged species. These species play an important role when it comes to the capacity of our forest ecosystems to adapt to changing environmental conditions.
#CoquiFossil; #PuertoRico; #CaribbeanForests; #FloridaMuseumOfNaturalHistory
Florida, Apr 7 (Canadian-Media): The bright chirp of the coquí frog, the national symbol of Puerto Rico, has likely resounded through Caribbean forests for at least 29 million years, phys.org news reports said.
Researchers attribute a 29 million-year-old partial arm bone fossil to the genus Eleutherodactylus. The ancient frog, which may have resembled this reconstruction, was less than half an inch long. Image Credit: Jorge Velez-Juarbe
A new study published in Biology Letters describes a fragmented arm bone from a frog in the genus Eleutherodactylus, also known as rain frogs or coquís. The fossil is the oldest record of frogs in the Caribbean and, fittingly, was discovered on the island where coquís are most beloved.
"It's a national treasure," said David Blackburn, Florida Museum curator of herpetology and the study's lead author. "Not only is this the oldest evidence for a frog in the Caribbean, it also happens to be one of the frogs that are the pride of Puerto Rico and related to the large family Eleutherodactylidae, which includes Florida's invasive greenhouse frogs."
Jorge Velez-Juarbe, associate curator of marine mammals at the Natural History Museum of Los Angeles County, found the fossil on a river outcrop in the municipality of San Sebastian in northwestern Puerto Rico. Velez-Juarbe and his collaborators' previous collecting efforts at the site uncovered fossil seeds, sea cows, side-necked turtles and the oldest remains of gharials and rodents in the Caribbean, dating to the early Oligocene Epoch, about 29 million years ago.
Still, "there have been many visits from which I have come out empty-handed over the last 14 years," he said. "I've always kept my expectations not too high for this series of outcrops."
On this trip in 2012, he combed the deposits for half a day without much luck when a small bone, partially exposed in the sediment, caught his eye. He examined it with his hand lens.
"At the moment, I couldn't wrap my mind as to what it was," Velez-Juarbe said. "Then once I got back home, cleaned around it with a needle to see it better and checked some references, I knew I had found the oldest frog in the Caribbean."
The ancient coquí displaces an amber frog fossil discovered in the Dominican Republic in 1987 for the title of oldest Caribbean frog. While the amber fossil was originally estimated to be 40 million years old, scientists now date Dominican amber to about 20 million to 15 million years ago, Blackburn said.
Based on genetic data and family trees, scientists had hypothesized rain frogs lived in the Caribbean during the Oligocene, but lacked any fossil evidence. The small, lightweight bones of frogs often do not preserve well, especially when combined with the hot, humid climate of the tropics.
Matching a single bone fragment to a genus or species "is not always an easy process," Velez-Juarbe said. It can also depend on finding the right expert. His quest for help identifying the fossil turned up empty until a 2017 visit to the Florida Museum where he had once been a postdoctoral researcher.
Today, frogs in the genus Eleutherodactylus, which includes the common coquí, dominate the Caribbean, having diversified into many different body forms and sizes. This fossil shows they have been in the region for at least 29 million years. Credit: Alberto Lopez Torres.
" I got to talk with Dave about projects, and the rest is now history," he said.
Possibly first arriving in the Caribbean by rafting from South America, frogs in the genus Eleutherodactylus, which encompasses some 200 species, dominate the region today.
"This is the most diverse group by two orders of magnitude in the Caribbean," Blackburn said.
"They've diversified into all these different specialists with various forms and body sizes. Several invasive species also happen to be from this genus. All this raises the question of how they got to be this way."
One partial arm bone may not tell the whole story of coquí evolution—but it's a start.
"I am thrilled that, little by little, we are learning about the wildlife that lived in Puerto Rico 29-27 million years ago," Velez-Juarbe said. "Finds like this help us unravel the origins of the animals we see in the Caribbean today."
#London&GermanResearcers; #Rainforests; #SouthPole; #WarmWeather
London (United Kingdom), Apr 1 (Canadian-Media): Evidence of rainforests found by researchers near the South Pole 90 million years ago is suggestive of exceptionally warm climate at the time, phys.org/news reports said.
Map of the drill site and how to continents were arranged 90 million years ago.
Image Credit: Alfred-Wegener-Institut
Analysis of the preserved roots from forest soil discovered by a team from the UK and Germany from the Cretaceous period within 900 km of the South Pole shows that the world at that time was a lot warmer than previously thought.
An international team of researchers led by geoscientists from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research in Germany and including Imperial College London researchers conducted the discovery and analysis. Their findings are published Apr 1 in Nature.
Co-author Professor Tina van de Flierdt, from the Department of Earth Science & Engineering at Imperial, said: "The preservation of this 90-million-year-old forest is exceptional, but even more surprising is the world it reveals. Even during months of darkness, swampy temperate rainforests were able to grow close to the South Pole, revealing an even warmer climate than we expected."
The work also suggests that the carbon dioxide (CO2) levels in the atmosphere were higher than expected during the mid-Cretaceous period, 115-80 million years ago, challenging climate models of the period.
Professor Tina van de Flierdt and Dr Johann Klages work on the sample of ancient soil. Credit: T. Ronge, Alfred-Wegener-Institut
The mid-Cretaceous was the heyday of the dinosaurs but was also the warmest period in the past 140 million years, with temperatures in the tropics as high as 35 degrees Celsius and sea level 170 metres higher than today.
However, little was known about the environment south of the Antarctic Circle at this time. Now, researchers have discovered evidence of a temperate rainforest in the region, such as would be found in New Zealand today. This was despite a four-month polar night, meaning for a third of every year there was no life-giving sunlight at all.
The presence of the forest suggests average temperatures were around 12 degrees Celsius and that there was unlikely to be an ice cap at the South Pole at the time.
The evidence for the Antarctic forest comes from a core of sediment drilled into the seabed near the Pine Island and Thwaites glaciers in West Antarctica. One section of the core, that would have originally been deposited on land, caught the researchers' attention with its strange colour.
The team CT-scanned the section of the core and discovered a dense network of fossil roots, which was so well preserved that they could make out individual cell structures. The sample also contained countless traces of pollen and spores from plants, including the first remnants of flowering plants ever found at these high Antarctic latitudes.
Illustration of the Antarctic rainforest. Credit: Alfred-Wegener-Institut/James McKay
To reconstruct the environment of this preserved forest, the team assessed the climatic conditions under which the plants' modern descendants live, as well as analysing temperature and precipitation indicators within the sample.
They found that the annual mean air temperature was around 12 degrees Celsius; roughly two degrees warmer than the mean temperature in Germany today. Average summer temperatures were around 19 degrees Celsius; water temperatures in the rivers and swamps reached up to 20 degrees; and the amount and intensity of rainfall in West Antarctica were similar to those in today's Wales.
To get these conditions, the researchers conclude that 90 million years ago the Antarctic continent was covered with dense vegetation, there were no land-ice masses on the scale of an ice sheet in the South Pole region, and the carbon dioxide concentration in the atmosphere was far higher than previously assumed for the Cretaceous.
Lead author Dr. Johann Klages, from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, said: "Before our study, the general assumption was that the global carbon dioxide concentration in the Cretaceous was roughly 1000 ppm. But in our model-based experiments, it took concentration levels of 1120 to 1680 ppm to reach the average temperatures back then in the Antarctic."