November 20, 2013
In 1834, Charles Darwin discovered a strange animal during his exploration of Chile’s southern coast. The creature, a small frog, was shaped like a leaf with a pointed nose, but appeared puffed up as if had been blown full of air, like a balloon. As it turned out, those fat male frogs hadn’t been gorging themselves on too many mosquitoes, but instead were enacting duties that earn them distinction as one of nature’s best dads. They were incubating several of their squirming babies in their vocal sac.
These peculiar animals, known as Darwin’s frogs, are today divided into two species, one that occurs in northern Chile, and another that lives in southern Chile and Argentina. When a female Darwin’s frogs lay her eggs, her mate keep a careful watch until the tadpoles hatch. The eager dad then swallows his young, allowing the babies to safely grow within his vocal sac until they turn into frogs and are ready to strike out on their own. Here, you can see a dutiful papa frog seemingly vomit up his living young:
Northerly Darwin’s frogs, however, have not been spotted in the wild since 1980. Researchers are nearly certain the species is extinct. Meanwhile, their southerly cousins are in steep decline and seem to be heading down extinction’s death row as well. For once, it seems that humans are not entirely to blame for these biodiversity disasters (unlike the western black rhino, which bit the dust a couple years ago after enduring decades of poaching for its valuable but medicinally worthless horn, used as an ingredient in traditional Chinese medicine). Instead, the deadly amphibian chytrid fungus, researchers report today in PLoS One, is likely to blame.
The chytrid fungus has popped up in amphibians in North and South America, Europe and Australia. The fungus infects the animals’ skin, preventing them from absorbing water and other nutrients. The fungus can rapidly decimate amphibian populations it comes into contact with, and has been called (pdf) “the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted, and its propensity to drive them to extinction” by the International Union for Conservation of Nature.
To identify chytrid as the likely culprit behind the Darwin’s frogs disappearance and decline, researchers from Chile, the UK and Germany conducted a bit of historical sleuthing. They dug up hundreds of archived specimens of Darwin’s frogs and closely related species dating from 1835 until 1989, and then tested them all for fungal spores (the problematic form of chytrid fungus was first recorded in the 1930s and reached epidemic-status around 1993, but researchers aren’t certain of when it first emerged). They also took around 800 skin swabs between 2008 and 2012 from 26 populations of still-living southern Darwin’s frogs and other similar frog species that live nearby.
Six of the old museum specimens, all collected between 1970 and 1978–just before the northern Darwin’s frog’s disappearance–tested positive for the disease. More than 12 percent of the living frogs tested positive for the fungal spores. In places where the Darwin’s frog has gone extinct or is experiencing drastic declines, however, rates of infection jumped to 30 percent in other amphibian species. Although these events don’t prove that the fungus killed the northern Darwin’s frogs and are now wiping out the southern species, the researchers strongly suspect that is the case.
Despite evidence that the disease has spread throughout the Darwin’s frog’s range, the researchers are not giving up on hope to save one of the world’s greatest dads from extinction. “We may have already lost one species, the Northern Darwin’s frog, but we cannot risk losing the other one,” Claudio Soto-Azat, the study’s lead author, said in a statement. ”There is still time to protect this incredible species.”
November 6, 2013
New species of insects, worms and other creepy-crawlers are announced on a monthly basis. Similarly, just last week, two new humpback dolphin species splashed into the headlines. And in October, news broke that early humans may have included fewer species than previously thought. This forces the question: what does it take to be a distinct species?
More than 70 official species definitions exist, of which 48 are widely accepted and used by scientists. And there’s no hard rule that scientists must stick to just one definition; some apply a handful of species definitions when approaching the topic. “I personally go to my lab every day and use five species definitions to conduct research,” says Sergios-Orestis Kolokotronis, a molecular ecologist at Fordham University, and co-author of the new dolphin study, published in Molecular Ecology. “And I sleep just fine amidst this uncertainty.”
Species definitions oftentimes do not translate from one organism to another. Dolphins may become isolated by distance and behavior that prevents them from reproducing, but in other cases–such as bacteria, which reproduce asexually–these distinguishing markers do not apply. Thus, the definition of what constitutes a species varies depending on whether scientists are studying dolphins, monkeys, insects, jellyfish, plants, fungi, bacteria, viruses or other organisms, Kolokotronis explains. And likewise, methods for investigating those species also vary. “Whoever figures out THE unifying species definition across the Domains of Life gets the Crafoord Prize!” Kolokotronis jokes.
In the case of the four dolphin species, each occupy different sections of ocean around the world, including in the Atlantic off West Africa (Sousa teuszii), in the central to western Indo-Pacific (Sousa plumbea), in the eastern Indian and western Pacific (Sousa chinensis) and in northern Australia (researchers are in the process of working on a name for that one–Sousa bazinga, anyone?).
While the humpback dolphins look quite similar, their genetics tells a different story. Researchers collected 235 tissue samples and 180 skulls throughout the animals’ distribution, representing the biggest dataset assembled to date for the animals. The team analyzed mitochondrial and nuclear DNA from the tissue, which revealed significant variations between those four populations. They also compared the skulls for morphological differences.
Although the line between species, sub-species and populations is a blurry one, in this case, the researchers are confident that the four dolphins are divergent enough to warrant the “species” title. The mitochondrial DNA turned up genetic signatures distinct enough to signal a separate species, and likewise, differences in the dolphins skulls supported this divergence. Although the nuclear DNA provided a slightly more confounding picture, it still clearly showed differences between the four species.
“We can confidently say that such strong divergence means these populations are demographically and evolutionarily isolated,” says Martin Mendez, a molecular ecologist at the American Museum of Natural History and lead author of the dolphin paper. “The key is that all the evidence–mitochondrial DNA, nuclear DNA and morphology–exhibited concordant patterns of distinct units,” he continues, which are “usually a must for species proposals.”
The genetic data the team collected does not have enough resolution to reveal how long ago the humpback dolphins diverged, and the team has yet to examine the drivers that fueled those speciation events. But Mendez and his colleagues have found that, in some dolphin populations, environmental factors such as currents and temperature play a role in separating populations and encouraging speciation. Different behaviors can help reinforce that separation, too. Most likely, however, geographic isolation plays a significant role in this case. “For populations living a couple hundred kilometers from one another, it’s perfectly possible for them to meet,” Mendez says. “But the distance from Africa to Australia is so great, it’s difficult to imagine those populations would ever be linked.”
Dolphins, Mendez and his colleagues are finding, evolve relatively quickly once isolated from parent populations. New cryptic–or hidden–species have similarly turned up in waters near South America. There may very well be other species of dolphins–or any type of animal, in fact–lurking undetected within an already-discovered species. ”This really applies to most taxa,” Mendez says. Across the board, “we’re adding many more species by looking at genetic data.”
While cryptic species almost certainly await discovery and will increase the head-counts of some organisms, in the case of ancient human ancestors, on the other hand, researchers now suspect that we’ve been too quick to pull the species card. An extremely well-preserved, approximately 1.8 million year-old Homo erectus skull discovered in Georgia alerted scientists to the potential revision. The skull’s odd proportions–large, but with a small brain case–prompted researchers to analyze variation between modern human and chimpanzee skulls, and compare those variations with other known human ancestor species. As the Guardian reports:
They concluded that the variation among them was no greater than that seen at Dmanisi. Rather than being separate species, the human ancestors found in Africa from the same period may simply be normal variants of H erectus.
If the scientists are right, it would trim the base of the human evolutionary tree and spell the end for names such as H rudolfensis, H gautengensis, H ergaster and possibly H habilis.
Ancient humans, of course, are no longer around for us to study their behaviors and mating tendencies, so anatomy has to do. For now, researchers are calling for more specimens to determine where that line will fall.
The line distinguishing two species may be a fuzzy one, but in the case of the dolphins, it is a big deal in terms of conservation. Australia, for example, is planning to design protective legislation for its new dolphin species, and Mendez hopes other countries will do the same.
Nonetheless, pondering the speciation of humans in dolphins in light of these two findings raises lots of questions: Are we fractally subdividing genetic information and brain cavity size to group and regroup organisms, or is there vast genetic diversity in even familiar species that we’ve yet to uncover? What does it mean for a species to gain or lose members of its family tree? The world and its organisms await more research.
July 1, 2013
Developing nations often have bigger problems to worry about than protecting wildlife. The limited resources available are directed towards fulfilling basic human needs such as food, sanitation, shelter and disease treatment and prevention. Rather than taking away from those human-oriented endeavors, developing countries rely upon donations largely from North America and Europe to address conservation. But the international donor community, it turns out, plays favorites when it comes to doling out funding for environmental protection–and those biases don’t necessarily have anything to do with the biodiversity at stake.
Until now, attempts to identify highly underfunded yet biodiverse countries have been hampered by poor and incomplete data on actual spending. To figure out which countries are the biggest losers when it comes to conservation, researchers decided to build the most complete database of global conservation funding to date.
To explore how international donors, governments and various organizations invested in conservation each year from 2001 to 2008, an international team of researchers analyzed around-the-world donations on a country-to-country basis. The database included all money a country spends on conservation, including funds procured from both outside and within the country. Those expenditures totaled $19.8 billion and represented the most complete database of conservation spending ever assembled. They created a statistical model that took into account factors ranging from country size, government effectiveness, political stability, GDP and biodiversity. Using statistical analyses, the authors teased out the underlying reasons driving whether countries do or don’t get funding.
For measuring biodiversity, they calculated the proportion of a species an individual country possesses, rather than just a species head-count, since some countries may contain just a handful of animals while another houses the bulk of the world’s population. They used mammals as a proxy for biodiversity because more information tends to be available for mammals than for other types of animals or plants, and because conservation dollars oftentimes favor the cute and furry over the scaly or slimy.
Upper income countries, as defined by the World Bank, distributed 94 percent of conservation funding, the team found, while countries in the lowest income bracket supplied just 0.5 percent. The U.S. and Germany topped the list of countries that provide aid to promote conservation; non-nation donors that contribute the most aid are the Global Environment Facility and the World Bank . The report also listed the 40 countries that receive the least funding given what would be expected based upon their size, biodiversity and GDP. From those, the top ten are:
- Solomon Islands
When the team plugged all of their data into a statistical model to try and figure out what’s driving these disparities, the results, published in the journal Proceedings of the National Academy of Sciences, explained 86 percent of the variation in how conservation money is spent each year. The most important factors for determining how funding is invested, they found, were the number of species, a country’s size (larger countries were favored for receiving funding over smaller ones) and the country’s GDP (higher GDPs were favored for receiving funding over smaller ones).
To see how conservation spending related to biodiversity, they compared funding data to the proportion of threatened biodiversity nations house. Significantly, they write, 40 of the most highly underfunded countries contain 32 percent of the world’s threatened species. The most strikingly disparate examples included Chile, Malaysia, the Solomon Islands and Venezuela. Highly underfunded countries also tended to occur in geographical groups, such as Central Asia, Northern Africa, the Middle East and parts of Oceania, meaning some species may miss out on protection across their entire range.
How did those 40 countries slip through the cracks? Some of the variation, they found, reflected political and historical biases. For example, predominantly Islamic countries receive less than half the funding as other countries that are equally biodiverse but follow a different religious and political scheme.
Other poorly funded countries, like Sudan and the Ivory Coast, suffered recent or ongoing conflicts, suggesting that donors may be hesitant to invest in conservation efforts in areas they perceive as being threatened by human strife. The researchers did not have enough data to include Somalia in the study, though they guess that it most likely falls within the severely underfunded category. “Globally, countries in conflict have high levels of both biodiversity and threat,” the authors write. “Donor reticence therefore deserves careful consideration because removal of funding may make a bad situation even worse.”
They do not address, however, whether or not nations in strife would be able to effectively manage conservation projects, though that likely depends on a case-by-case basis. Afghanistan, for example, declared its first national park in 2009, and long-term conservation efforts in the Central African Republic were threatened but still managed to prevail when violence broke out earlier this year.
Targeting underfunded areas that contain high levels of biodiversity, the authors think, could make a greater impact for protecting species than investing that money elsewhere, where ample resources already exist. Strengthening conservation efforts in the places with the highest biodiversity but least funding support “may therefore reduce short-term biodiversity losses with appreciably greater efficiency than would current spending patterns,” they write.
Because the most underfunded countries tend to be developing nations, they continue, a relatively small investment on the part of the international community could make a significant difference for wildlife there. They add, “Our results therefore suggest that international conservation donors have the opportunity to act now, in a swift and coordinated fashion, to reduce an immediate wave of further biodiversity declines at relatively little cost.”
May 23, 2013
Most people consider saving the Amazon rainforest a noble goal, but nothing comes without a cost. Cut down a rainforest, and the planet loses untold biodiversity along with ecosystem services like carbon dioxide absorption. Conserve that tract of forest, however, and risk facilitating malaria outbreaks in local communities, a recent study finds.
Nearly half of malaria deaths in the Americas occur in Brazil, and of those nearly all originate from the Amazon. Yet few conservationists consider the forest’s role in spreading that disease. Those researchers who do take malaria into account disagree on what role forest cover plays in its transmission.
Some think that living near a cleared patch of forest–which may be pockmarked with ditches that mosquitoes love to breed in–increase malaria incidence. Others find the opposite–that living near an intact forest fringe brings the highest risk for malaria. Still more find that close proximity to forests decrease malaria risk because the mosquitoes that carry the disease are kept in check through competition with mosquitoes that don’t carry the disease. Most of the studies conducted in the past only focused on small patches of land, however.
To get to the bottom of how rainforests contribute to malaria risk, two Duke University researchers collected 1.3 million positive malaria tests from a period of four-and-a-half years, and ranging over an area of 4.5 million square kilometers in Brazil. Using satellite imagery, they added information about the local environment where each of the cases occurred and also took rainfall into account, because precipitation affects mosquitoes’ breeding cycles. Using statistical models, they analyzed how malaria incidences, the environment and deforestation interacted.
Their results starkly point towards the rainforest as the main culprit for malaria outbreaks. “We find overwhelming evidence that areas with higher forest cover tend to be associated with higher malaria incidence whereas no clear pattern could be found for deforestation rates,” the authors write in the journal PLoS One. People living near forest cover had a 25-fold greater chance of catching malaria than those living near recently cleared land. Men tended to catch malaria more often the women, implying that forest related jobs and activities–traditionally carried out by men–are to blame by putting people at greater risk for catching the disease. Finally, the authors found that people living next to protected areas suffered the highest malaria incidence of all.
Extrapolating these results, the authors calculated that, if the Brazilian government avoids just 10 percent of projected deforestation in the coming years, citizens living near those spared forests will contend with a 2-fold increase in malaria by 2050. “We note that our finding directly contradicts the growing body of literature that suggests that forest conservation can decrease disease burden,” they write.
The authors of the malaria study do not propose, however, that we should mow down the Amazon in order to obliterate malaria. “One possible interpretation of our findings is that we are promoting deforestation,” they write. “This is not the case.” Instead, they argue that conservation plans should include malaria mitigation strategies. This could include building more malaria detection and treatment facilities, handing out bed nets and spraying for mosquitoes.
This interaction between deforestation and disease outbreakis just one example of the way efforts to protect the environment can cause nature and humans to come into conflict. Around the world, other researchers have discovered that conservation efforts sometimes produce negative effects for local communities. Lyme disease–once all but obliterated–reemerged with a vengeance (pdf) in the northeastern U.S. when abandoned farmland was allowed to turn back into forest. Human-wildlife conflict–including elephants tearing up crops, tigers attacking livestock, and wolves wandering into people’s backyards–often comes to a head when a once-declining or locally extinct species makes a comeback due to conservation efforts.
“We believe there are undoubtedly numerous ecosystem services from pristine environments,” the PLoS One authors conclude. “However, ecosystem disservices also exist and need to be acknowledged.”
April 26, 2013
You probably haven’t heard of the world’s second rarest ape, the cao vit gibbon. Scientists know of only one place the species still lives in the wild. In the 1960s, things got so bad for the cao vit gibbon that the species was declared extinct. But in 2002, to the surprise and elation of conservationists, the animals—whose shaggy coats can be a fiery orange or jet black—turned up along Vietnam’s remote northern border. Several years later, a few gibbons were found in China, too.
Also known as the eastern black-crested gibbon, the cao vit gibbons once covered an expanse of forest spanning from southern China and northern Vietnam just east of the Red River, but today only about 110 individuals survive. This gibbon is highly inclined to stick to the trees—in a previous study, during more than 2,000 hours spent observing gibbons in the field, researchers saw only once and very briefly one young male cao vit gibbon come down from the canopy and walk on a rock for a few seconds. Population surveys based on watching the animals in the branches reveal that the gibbons live in 18 groups scattered throughout the area. That makes it the second least populous species of ape, just after the Hainan gibbon, another type of extremely rare gibbon living in the same area of Asia.
In 2007 and 2009, Vietnam and then China hustled to establish special protected areas dedicated to preventing the cao vit gibbon’s extinction. Much of the area surrounding the remaining populations of gibbons is quickly being converted to agricultural fields and pasturesor cut down to make charcoal to sell and use at home, a common practice in the area. Hunting—though illegal—is also an issue, as exotic wild meat dinners are popular with locals in the region.
For an endangered species to recover rather than just survive, it needs to grow in numbers. But any given patch of land can only support so many animals given the amount of food and space that’s available. If populations exceed this threshold—called a carrying capacity—then animals will either starve, get picked off by predators or have to move somewhere else.
Researchers from Dali University in Yunnan, the Chinese Academy of Sciences in Kunming and the Chinese Research Academy of Environmental Sciences in Beijing wanted to find out how much of the protected forest the cao vit gibbons had expanded into, and also how many animals that pocket of land could eventually support. To answer this question, they turned to high-resolution satellite images, describing their results in the journal Biological Conservation.
Once they acquired aerial images of the gibbons’ habitat, they classified it into forest, scrub, shrub land and developed areas. This was important because gibbons can only live high in forest canopies, meaning the latter three categories were out of bounds for potentially supporting the animals. Overall, the area could be divided into five different zones that were split apart by either roads or rivers. From there, the researchers plugged the data into computer models that ranked possible gibbon habitat from high to low quality.
Their results revealed several bits of news, some good and some bad. First, from the models it seems that 20 groups of gibbons could eventually live in the protected forest areas before the population reaches its carrying capacity threshold. However, as human development creeps closer and closer, that disturbance could lower that figure. As things stand, the gibbons will likely reach their carrying capacity in the current habitat in 15 years, which doesn’t bode well for building up the species’ numbers.
There are a couple options. The protected area isn’t all great habitat, it turns out. Some of it is just mediocre for gibbons. If that span of forest could be improved, it could eventually support up to 26 groups of animals. The researchers also identified two other potential areas where gibbons could live if they could somehow manage to travel there (no gibbon has ever been known to cross a river or a road). But these patches of welcoming forest, located in Vietnam, are not protected, so they likely will not remain forests for long. If the government decided to protect those areas, the researchers write, they could serve as places for cao vit gibbons to live in the future, especially if narrow corridors of trees connecting the two areas were protected and restored as well.
If these patches of forest were protected, gibbons would not be the only species to benefit. Numerous other species of primates and monkeys, civets, pangolins, porcupines, birds, bats and many more depend upon those last remaining jungle habitats for survival. “In summary, the last remaining population of cao vit gibbon is nearing its carrying capacity in the current remaining forest patch,” the authors write. “Forest protection and active forest restoration using important food tree plantings to increase habitat quality and connectivity should be the most critical part of the ongoing conservation management strategy.”