Modern biogeography—the study of the distribution of species—still relies heavily on the above map, despite the fact that it was drawn by the field’s founder, Alfred Russel Wallace, in 1876. The map indicates regions of historical species mixing, pointing out, for instance, that a mouse in North Africa is more likely and able to mix with its European brethren than its South African cousins. This week researchers have revealed a new and improved biogeographical map, published in Science, which they hope will become the new baseline for ecological and evolutionary studies as well as conservation efforts.
Despite its romantic holiday association, mistletoe has long been villainized in ecology circles for being a parasite—the vine wraps itself around trees and steals nutrients from them to survive. Nobody likes a mooch, but researchers in Australia have found that this parasitic plant is not all bad. In fact, their findings [pdf] published in the Proceedings of the Royal Society of Biological Sciences this July suggest mistletoe may actually be a keystone species in forest ecosystems. The plant is relatively sparse but plays a critical role in maintaining the overall health and diversity of species in its environment.
The manmade changes pushing the planet toward a critical transition
Nature changes gradually—until it doesn’t. As the changes in an ecosystem pile up, they can push the system past a “critical threshold,” and then the change can become extremely fast (in relation to geological timescales) and unstoppable. And in a review in the journal Nature, researchers suggest that the same thing is happening to the whole world: Humans could be driving Earth’s biosphere towards a tipping point beyond which the planet’s ecosystems will collapse abruptly and irreversibly.
This global ecosystem collapse has occurred before, most recently about 12,000 years ago with the last transition from a glacial period to the current interglacial (i.e., warm) period, say the review authors. Over the relatively short period of 1,000 years, fluctuations in the Earth’s climate largely killed off about half the large mammal species, along with birds, reptiles, and a few smaller mammal species. The millennium-long shift was triggered by rapid global warming, and once this warming pushed the planet past its tipping point, the end of the 100,000-year-old ice age became inevitable, giving way to the current 11,000-year-old interglacial era.
Flukes that parasitize amphibians
The enemy of my enemy is my friend—especially if I’m a frog and my enemies are competing parasites. A recent study in PNAS found that frogs populations exposed to a more diverse set of flukes actually had lower rates of infection, with fewer frogs in the group afflicted with tiny hitchhikers.
Researchers at the University of Colorado-Boulder bred Pacific chorus frogs in a lab and put their tadpoles in different tanks with anywhere from one to six different types of flukes. On average, 40% of the frogs that came into contact with only a single fluke species developed infections, while 34% of frogs exposed to four flukes and 23% of frogs exposed to six flukes were infected (the numbers for two, three flukes followed a roughly similar trend). Additionally, some of the fluke species make frogs sicker than others, and oddly enough, the frogs exposed to a greater variety of flukes had a lower proportion of infections from these dangerous species.
Crawling my way to a healthier immune system.
Bacteria are practically everywhere around us, including on and inside you, but that is in many ways a good thing. For instance, having a diverse set of microbes living on your skin might help prevent allergies. A new study published in PNAS links two factors related to how microbes might affect our health: the observation that diversity of microbes on a person is related to the diversity of microbes in their environment, and the hygiene hypothesis, which suggests that the modern uptick in allergies and autoimmune diseases is caused by childhood under-exposure to bacteria.
For a while now, scientists have known that kids living on farms are less likely to have allergies or asthma. Being around livestock means the farm kids are also around a more diverse set of bacteria than city kids living in an apartment. In this new study, scientists swabbed the skin bacteria of 118 Finnish kids, some who lived in rural areas and some who lived in urban areas. They also tested the kids for levels of an antibody called IgE, high levels of which indicate hypersensitivity to allergens, or what is known as atopy. Lastly, they surveyed the parents about plant diversity around their homes.
Sequencing the DNA in a scoop of dirt can tell scientists what creatures are living nearby, a new study using soil from safari parks shows, and the amount of DNA present can even tell how many individuals of each species there are, which could allow field biologists to get preliminary surveys of species. But though the team managed to identify nearly all the species they had expected in the parks, from wildebeest to elephants, they are still addressing how to take samples that accurately represent the area’s biodiversity—one would have to avoid elephant latrines or wildebeest sleeping areas, for instance—and there is the additional problem that rare or small creatures, like insects, might easily be missed. That said, it’s still an unusual and interesting way to take a look at an area’s inhabitants without actually tracking them down.
Read more at Scientific American.
Image courtesy of malcyzk / flickr
It’s no secret that an alarming number of species around the world, especially vertebrates, are in trouble. But is the notion that the Earth is on the brink of a sixth major extinction event—the first since the dinosaur die-off—true, or alarmist? In Nature this week, a team of scientists sought to answer the question directly by counting as many species (and extinctions) as they could in the fossil record and the recent historical record. The result is gloomy news: There’s still a chance to avert much of the crisis, but if nothing changes, such a mass extinction event really could happen in the span of just a few centuries.
Mass extinctions include events in which 75 percent of the species on Earth disappear within a geologically short time period, usually on the order of a few hundred thousand to a couple million years. It’s happened only five times before in the past 540 million years of multicellular life on Earth. (The last great extinction occurred 65 million years ago, when the dinosaurs were wiped out.) At current rates of extinction, the study found, Earth will enter its sixth mass extinction within the next 300 to 2,000 years. [MSNBC]
That range of time the researchers give is so large because of the great diversity of life—it makes it hard to track exactly how many species are disappearing, and how quickly. (Indeed, DISCOVER has covered how biologists are discovering many new species these days just as those species face extinction). So Anthony Barnosky and his team made conservative estimates based on the available evidence. For instance, they pegged the rate of mammal extinction at 80 species out of a total of 5,000-plus in the last five centuries. That may not sound like much, but when you consider the speed at which things typically happen on a geologic scale, it is a faster rate of species loss than the previous five mass extinctions saw, scientists believe.
Sunday marked the opening of the worldwide tiger summit, which brought together high-level representatives from the 13 tiger-habitat countries, including Russia and China, to discuss the best plan to save the tigers. The meeting goes through Wednesday.
Only about 3,200 tigers remain in the wild, and without help experts say populations will start to go extinct in less than 20 years.
“Here’s a species that’s literally on the brink of extinction,” said Jim Leape, director general of conservation group WWF. “This is the first time that world leaders have come together to focus on saving a single species, and this is a unique opportunity to mobilise the political will that’s required in saving the tiger.” [BBC News]
The working plan includes provisions to decrease poaching and smuggling of the tigers and calls for more protected habitats. Researchers say that if tigers are left alone and provided with enough habitat and prey, the population could double in 12 years.
What does it take to make a wellspring of biodiversity like the Amazon rainforest? A huge mountain range, a blast of heat, and a little time.
A pair of studies in this week’s edition of Science attempt to sort through tropical natural history and reach the root causes of Amazonia’s embarrassment of biological riches. The first, led by palaeoecologist Carina Hoorn, points to the influence of the Andes Mountains, the spine of South America that runs up its western coast. Sometime between about 35 and 65 million years ago, colliding tectonic plates sent the Andes bulging up. According to the researchers, the birth of a mountain range set of an ecological chain reaction.
The rising mountains that resulted from the uplift blocked humid air from the Atlantic, eventually increasing rainfall along the eastern flank of what became the Andes that eroded nutrient-loaded soils off the mountains. The Andes also kept water from draining into the Pacific, helping form vast wetlands about 23 million years ago that were home to a wide range of mollusks and reptiles. [LiveScience]
While the temperature effects of climate change are expected to be less dramatic in the equatorial regions, the cold-blooded tropical animals that live there may be in for a dramatic shock.
A study published this week in Nature focused on these cold-blooded animals–including insects, amphibians, and lizards–whose body temperatures are not constant, but instead rise and fall with the temperature of their environment. The researchers found that these creatures show great increases in their metabolism from slight changes in temperature; the metabolic increases were on the order of twice that of warm-blooded animals.
“The assumption has been that effects on organisms will be biggest in the place where the temperature has changed the most,” [first author Michael] Dillon said. “The underlying assumption is that … no matter where you start, a change means the same thing. But with physiology, that’s rarely the case.” [Scientific American].
This means that though climate change will be more extreme in toward the Earth’s poles, the cold-blooded animals that live near the equator (where changes should be milder) may react more strongly to the changes.