Category Archives: Scientific semantics

Surviving Fires, Global Warming — With Naps

The unprecedented Black Saturday bushfires in the countryside surrounding Melbourne in 2009 left 1 million acres of Australian landscape charred. Squeaked mousey marsupial after losing its insect hunting grounds: “Yawn.”

Wildfire-adapted wildlife has to cope with more inferno-related threats than just the flames.

The scorched earth left behind by wildfire can be bereft of the plants and insects that are used for food by many small animals. As they move through the black landscape, these animals can lose their camouflage and succumb to predators.

To survive these tough times, some antechinuses — marsupial mice in Australia and New Guinea — amplify their siesta-style torpor, taking longer power naps every day.

That reduces their daily energy needs, allowing them to get by on less while the forest recovers around them.

“There’s a perception that bushfire affects animals through the direct effects of fire killing individuals,” said Australian National University researcher Sam Banks.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

“Certainly, this happens,” Banks said. “But it seems to be the availability of crucial resources in the post-fire environment that determines whether animal populations persist.”

In 2009, Banks led a group of scientists that aimed to use the aftermath of the fires as a laboratory to investigate how two species of small marsupials survive and recolonize after bushfire.

The team found that agile antechinuses were more than twice as likely, compared with bush rats, to continue inhabiting a scorched habitat after a fire.

The antechinuses — which eat insects and, despite their outward resemblance, are not rodents — were 30 percent as likely to inhabit a burned patch of land compared with an unburned one. The bush rats (they are native rodents) were 12 percent as likely.

“It always seemed to me slightly unusual that such a small mammal with high energetic requirements would persist in burnt habitat with — presumably — reduced food availability,” Banks said.

An agile antechinus. Photo by Michael Sale/Flickr
An agile antechinus. Photo by Michael Sale/Flickr

New research suggests that the use of torpor could explain the antechinuses’ reluctance to flee post-fire landscapes.

“It’s interesting to see that they might have some physiological responses that would enable them to cope with tough periods,” Banks said, after reading the new paper, which was published in the journal OIKOS by a team of scientists from Australia’s University of New England.

“For antechinus, they shelter in hollow trees, all but the most decayed of which remain standing after fire,” Banks said. “I guess the torpor response helps them deal with the lack of food.”

The University of New England paper tracked brown antechinuses, which closely resemble agile antechinuses, in and near a 1,000-acre prescribed fire in a national park in southeastern Australia. The researchers focused on females, in which torpor is more pronounced.

One of the five females being studied in the burned area took shelter from the fire beneath rocks, where it was killed by the flames.

The other four took shelter in trees, where they survived. Before the fire, they had spent about half their time in states of torpor, in which metabolism slows down and energy is conserved. The same was also true for a control population studied.

After the fire, the four female survivors spent most of their time in torpor. The average power nap rose in length to an average of three to five hours — up from between one and three hours.

One female clocked up more than ten hours of nonstop torpor after the fire. That doubled the group’s pre-fire torpor record.

These marsupials are pulling a trick known as heterothermy.

A heterothermic mammal or bird can display the characteristics of a warm-blooded endotherm, churning through energy as it ferrets about for food and mates. But when it needs to slow its demand for energy, it can hibernate, or enter a briefer form of daily hibernation known as torpor, displaying characteristics of a cold-blooded ectotherm — such as a snake.

The list of heterotrophs is long — check out this table from a Current Biology article by University of New England professor Fritz Geiser. Geiser also led the antechinus torpor study published in OIKOS.

Current Biology
Current Biology

Some scientists have argued that heterothermy helped some mammals survive the mass extinction that killed the dinosaurs.

As earth’s biosphere plunders into the anthropocene, and as greenhouse gas pollution drives longer and harsher wildfire seasons, these marsupials’ heterothermy may give them a fire-resistant evolutionary upper hand.

It is “likely,” Geiser wrote in his 2013 Current Biology essay, that “opportunistic heterotherms may be better equipped” than other species to cope with “anthropogenic influences such as habitat destruction, introduced species, novel pathogens and specifically global warming.”

That, he wrote, is because these animals have “highly flexible” energy needs, can limit foraging and avoid predators.

When Hybrids Go Wild

By John Upton

Q: How do you make a hybrid trout go wild?

A: You wait.

From a survival-of-the-fittest perspective, a domesticated animal is a poor facsimile of its wild relative. That’s why a salmon or a trout reared in a hatchery is less likely to survive in the ocean and return safely to its home river come spawning time.

When domesticated creatures are mixed with a population of wild ones, such as through fish-stocking programs, their domesticated genes, many of which are ill-suited to the idiosyncrasies of the new environment, can be passed on to the next wild-dwelling generation. The genetic contamination lingers so long in the newly hybridized population that wildlife management policies generally consider it to be permanent.

The good news for a hybrid-wearied world is that recent research suggests that a wild trout population’s newly-hybridized traits could be shed quickly — even if some of the hybrid DNA sticks around.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

Ontario and Concordia University researchers reared brook trout from two hybridized populations and from one wild population in Ontario’s Algonquin Park. They also obtained trout from a nearby hatchery. The four populations were mixed equally in holding tanks, then released into three small, hitherto trout-free lakes in the North Shore region of Lake Huron.

The researchers sampled from the three lakes five months later, testing how well each of the strains had survived the rigors of the new environment. By then, most of the fish had died, which is normal after brook trout are planted

in Ontario waters. Mortality in one of the lakes was 96 percent. In the other two lakes: 80 percent. The scientists found that members of the hybrid and wild populations had similar chances of survival — and that they all fared better than their hatchery cousins.

One of the hybrid populations studied had last been contaminated with hatchery fish some five generations earlier. The other had been hybridized for 11 generations.  The results, the scientists wrote in a paper published recently in Evolutionary Applications, “suggest that within five to eleven generations, selection can remove introduced foreign genes from wild populations.”

The findings are a reminder of the fast pace at which evolution is capable of working.

“Allowing natural selection to act for relatively few generations can produce hybridized populations that closely resemble nearby non-hybridized populations — both physically and ecologically,” said Concordia University’s Andrew Harbicht, one of the researchers behind the study.

“Certain genetic vestiges will persist into the future over the long term. But, generally, the hybrids will behave ecologically similarly to their wild predecessors after a fairly short time period,” Harbicht said.

Natural History of Sex

By John Upton

If you could exchange the orgasmic gift of mammal-style intercourse for the messy ritual of dribbling fluids together, would you?

If you were the lineage of the world’s fish, then the latest evidence suggests that the answer to that unlikely conundrum would be, ‘Yes,’ to the great surprise of scientists documenting backbone-baring animals’ earliest known instances of internal fertilization.

We’re not talking about pudgy, panting penetration following happy hour pitchers. We’re talking rock-hard prehistoric fish, dermal claspers and paired dermal plates — locked, hundreds of millions of years ago, in ocean-floor embraces.

Bow guppy bow wow.

antiarchs
Illustrated by Perry Shirley.

A new scientific study peers into the most intimate moments in the lives of fish of several closely related ancient fish genii — MicrobrachiusPterichthyodes and Bothriolepis. Each was an antiarch, which was a heavily-armored order of fish known as placoderms. Placoderms were early gnathostomes, an infraphylum also called boned vertebrates, which includes all the fish alive today.  Gnathostomes started the branch on our evolutionary family tree that blossomed into lizards, birds and apes.

These long-dead fish were caught in the act of possessing the organs needed for sexual penetration. In a question over which came first, be it fish intercourse or external spawning, the answer would seem to be the former.

(The word antiarch means “opposite anus,” by the by, because a scientist once mistook a fossil’s mouth for its ass. And, while we’re at it, one of the species studied was M. dicki. Because somebody couldn’t help themselves.)

We’ve included a sketch of this primal love making below. Just make sure there are no underaged fish fossils in the room.

Mating Microbrachius
Adapted from a figure in Nature showing Microbrachius mating.

Is there anything cuter than fish that lock arms like that at a time like that? In real life, the width of that embracing scene would have been an adorable inch and a half.

We’re not sure if those are expressions of ecstasy — or the shocked looks that are to be expected when scientific method walks through the doors of ancient history during the most intimate of hypothesized moments. But we did confirm with Flinders University paleontology professor John Long that those big holes are where the eyes and nostrils would be. Because we didn’t want to get anything ass-backwards.

By now you might be wondering such things as, What does this have to do with me? If I took the right medicine, could I lead a life like that? And, How can I not think about this next time I’m bonking my boyfriend, or rolling in the hay at that haystack that my wife and I both like; won’t somebody please come and scoop the vision of adorable ancient randiness from my braincase? Aarrrggghhhhh.

We don’t know the answers to all your implied imaginary questions. What we do know comes from a study published Sunday in Nature by a large team of scientists led by Long.

The scientists analyzed fossils of the three genii that we mentioned earlier, and found in the males what they believe to be evidence of dermal claspers. They also found what they take to be the paired dermal plates of their female counterparts. Place those together and you’ve got yourself some internal fertilization, Velcro style.

The researchers write that the claspers found in these fossils resemble those of ptyctodonts, an order of placoderms that came after the unfortunately-named antiarchs. Those similarities, they wrote, suggest that “all placoderm claspers are homologous,” and that “internal fertilization characterized all placoderms.”

And they say that implies that spawning, which is so popular with the gnathostomes of today, must be an evolutionary adaptation that began with internal fertilization, even though such a transformation had been regarded as implausible.

“The complex physiology of fish that internally fertilize precludes a reversion back to spawning in water,” Long told us. “Yet our analysis shows it was the most likely explanation.”

How are emus related to ostriches?

By John Upton

Which came first — the chicken or the egg?

It’s inside an egg that genes combine to code for an individual, so we’re going to go with ‘the egg.’ Next question, please.

Which came first — the ostrich or the emu?

Looking at pictures of these flightless birds, you’d be forgiven for mistaking them for kissing cousins. They’re both swift-footed birds with buns of feathers hitched high — alluring outfits that show off their slender legs and necks.

emu and ostrich
Illustrated by Perry Shirley.

But they’re not as closely related as they might at first seem.

Ostriches and emus are both ratites — members of a group of large flightless birds endemic to the Southern Hemisphere. Ratites were all thought to have descended from a common ancestor; examples of what scientists dub vicariance biogeography, or convergent evolution, in which members of once-conjoined populations become geographically separated, such as through the geological manifestation of a new river, gulf, or mountain, and then pursue their own evolutionary trajectories. In the case of ratites, they were thought to have gone their separate ways following the bust-up of Gondwana, from where their presumed ancestor was thought to have hailed.

Just a decade ago, in his book The Ancestor’s Tale: A Pilgrimage to the Dawn of Evolution, famed biologist and writer Richard Dawkins described ratites as a “truly natural” group. “Ostriches, emus, cassowaries, rheas, kiwis, moas and elephant birds really are more closely related to each other than they are to any other birds,” he wrote. “And their shared ancestor was flightless too.”

Dawkins’ statement reflected leading science from the time. But advances in molecular phylogenetics have since revealed the folly of longheld assumptions about ratite evolution. The apparent similarities between different species of ratites are now thought to have been the consequence of convergent evolution — the independent evolution of similar features by different species in far-flung places that inhabit similar ecological niches.

It seems that flightlessness just makes sense in the right environments. Research in recent years has revealed that selection pressures independently pushed the forebears of today’s ratites to shrink their wings, bloat their bodies, flatten their sternums, and evacuate the skies.

Several years ago, University of Florida researchers used BUCKy software to analyze the genomes of various birds, and found that the ratite family tree includes a surprising cousin — tinamous, an order of grouse-resembling birds from Central and South America. These birds spend much of their lives on the ground, but many of the species are perfectly capable of flying. The tanimous were found to be more closely related to emus then they were to ostriches, providing further evidence of the independent evolution of flightlessness in different ratites. The findings were published in the journal Systematic Biology:

(Credit: Systematic Biology)
(Credit: Systematic Biology)

“The independent evidence we obtained provided strong corroboration of the hypothesis that nonostrich paleognaths form a clade,” wrote the three scientists involved with the research in their paper. “This sharply alters our understanding of the evolutionary history of the flightless ratites by providing support for multiple losses of flight. It remains possible there was a single loss of flight early in paleognath history followed by a regain of flight in tinamous, but this is unlikely because the loss of flight appears to be a relatively easy transition for birds whereas the loss followed by the regain of flight has never been documented. The hypothesis that flight has been lost multiple times in the ratites suggests that some of the most distinctive morphological characters in ratites arose through convergent evolution.”

We asked one of the authors of the paper, Edward Braun, an associate professor in the university’s biology department, how this information and similar analyses could help answer our question. Which species is older — the emu or the ostrich?

Braun said that’s a tough question to answer; but he suggested a couple of alternatives, which he then answered.

“One valid question is, ‘When did ostriches start looking like ostriches, and when did emus start looking like emus?'” Braun said. “I suspect that, if the question is asked that way, the answer is, ‘About the same length of time.'”

“On the other hand, another way of asking the question is, ‘When did ostriches separate from other extant birds, relative to emus?’ The answer to that is clear. Ostriches have no close relatives. Ostriches separated from other birds a long time ago; probably in the Paleocene [66 to 56 million years ago], since there are middle Eocene fossils that are probably now extinct parts of the ostrich lineage. Emus are more closely related to rheas, kiwis, and quite close to cassowaries.”

Enjoy this fun video of emus and an ostrich playing with a motorized ball, which helps to reveal differences in the appearances of the species:

Why don’t we measure biodiversity?

By John Upton

Vast resources are plowed into measuring the metrics associated with global warming. Calculations reveal that American and European greenhouse gas emissions are falling while China’s are rising, and that more carbon dioxide is being pumped out worldwide every year than had been the case the year before. We know that carbon dioxide levels passed a record-breaking 400 parts-per-million point in May, well above the preindustrial level of 280 ppm, before dipping in line with normal seasonal fluctuations — that knowledge is courtesy of air monitoring in Hawaii and the findings of ice-core studies. And gravity-measuring satellites are used to estimate the rate at which glaciers are melting — revealing that despite harboring just 1 percent of the world’s land ice, these thawing rivers of ice are responsible for 29 percent of the rise of sea levels.

The results of these measurements don’t just keep us awake at night. They help policy-makers target efforts to reduce emissions and to prepare communities for changes in the climate.

But what about biodiversity?

Although the world is rallying around efforts to come to terms with its climate problem (even if not enough is being done to actually solve that problem), it is failing to measure the alarming decline of biodiversity, which by one recent estimate has fallen 30 percent in 40 years. It is not investing the resources needed to track the genetic stockpile contained in the cells of plants, animals, mushrooms and other forms of life as forests are bulldozed, rivers are diverted and acidifying oceans are overfished.

Every time a species or a jungle is lost, and every time environmental tumult helps generalists (such as ring-billed gulls) outcompete specialists (such as piping plovers), the world loses some of its genetic code. That code is critically important. It can help an ecosystem weather changes in the, well, in the weather, which is happening now more than ever in human history. It can help sustain a myriad of complex food chains that underpin the very functioning of the natural world. And it can present humans with chemical compounds that prove useful as new drugs or foods.

If we are to get a handle on the specifics of the biodiversity crisis, which we must do if we are to effectively manage the problem, then more scientists need to be trained and employed and provided with the resources needed to advance their fields.

Aware of the problem of falling biodiversity, the United Nations last year formed the Intergovernmental Platform on Biodiversity and Ecosystem Service. The group is structured a bit like the Intergovernmental Panel on Climate Changeits primary function is to review, assess, synthesize and share information about biodiversity with policy makers.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

The group held meetings in Malaysia this week to discuss two main topics: the measurement and assessment of genetic and biological resources; and the calculation of the value of key ecosystem services.

The conclusion: The world just isn’t doing enough to measure biodiversity.

“Of the estimated 10.8 million species on land and in the oceans, less than 2 million have been scientifically described,” IPBES chairman Zakri Abdul Hamid, science advisor to Malaysia’s prime minister, said in a statement published Wednesday at the end of the three days of talks. “If we don’t know what species there are out there, we don’t know what niche they fill in a healthy ecosystem or perhaps in remedying some human condition.” More from the statement:

Most world nations – unanimously committed to protecting biodiversity – nevertheless cannot measure and assess their genetic and biological resources, nor the value of key ecosystem services nature provides to them, international experts from 72 countries warned today.

In addition to taxonomists, nations lack economists able to put a value on the water purification, storm protection and other services of nature, which would inform trade-off choices in development planning. And fewer still deploy social scientists to estimate nature’s non-economic (e.g. cultural) values, or to find ways to effect needed changes in human attitudes and behaviour.

“There’s an old saying: We measure what we treasure. Unfortunately, though we profess to treasure biodiversity, most nations have yet to devote adequate resources to properly measure and assess it along with the value of ecosystem services,” Zakri said. “Correcting that is a priority assignment from the world community to IPBES.”

Research: Bat-killing fungus arrived from afar

By John Upton

A ripple of bat deaths has grown since 2006 to become millions of Chiroptera deep, stretching out from its New York epicenter into five Canadian provinces and west at least as far as Missouri. The latest state to be affected was Minnesota, where infected bats were discovered in two parks.

The dead bats were all members of species that hibernate — and they succumbed to white nose syndrome. The disease is caused by a fungus that eats away at their wings and faces.

Little brown bats are among the worst affected. These adorably tiny bats were common throughout Eastern America as little as a decade ago, sucking down mosquitoes and other pests during their nocturnal maunders. Now the species appears to be on the verge of being listed as federally endangered.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

Mammals appear to have developed high body temperatures to help stave off infections of fungi. But hibernating bats have a chink in that armor: When they hibernate, their body temperatures plummet. And when most bats hibernate, they huddle together, which helps the fungal infection spread through the slumbering colony.

What caused this fast-moving fungus to suddenly begin attacking bats? Did it go rogue, evolving from a soil eater into a devourer of bat flesh? Or is it an invasive species that arrived from some far-flung place?

A pair of Wisconsin-based U.S. Forest Service scientists studied the DNA of the disease along with that of more than a dozen species of other fungi found growing in bat caves in the eastern U.S. What they found, first and foremost, was that the pathogen was not quite what everybody thought it was.

Scientists have called the disease Geomycetes destructans since it was identified in 2009. But the recent research, described in the journal Fungal Biology, indicates that the fungus is actually a member of the genus Pseudogymnoascus. Hence, it has been reclassified P. destructans.

Of the other species of Pseudogymnoascus fungi sampled in the studied hibernacula, the scientists reported that none were closely related to P. destructans. That’s significant, because it suggests that white-nose syndrome arrived in New York from some other part of the world, perhaps on the shoes of a traveler or shipped in as a few spores with freight.

Researcher Andrew Minnis said the study is part of a wider effort to find a way to protect bats from the fungus. “Once key elements of this [fungus] species’ biology, including mechanisms of pathogenicity, are identified, it will be possible to target them,” he said.

Once it was realized that many related fungi were present in bat caves, but weren’t killing bats, “thoughts arose that these species could be used for comparative purposes — to understand why P. destructans is different,” he said. Following the findings from this study, “further and more informed comparative work can now be performed.”

Confirmed and suspected white-nose syndrome cases. Map updated August, 2013 by the U.S. government.
Confirmed and suspected white-nose syndrome cases. Map updated August, 2013 by the U.S. government.

Was Azaria Chamberlain killed by a native or invasive dog?

By John Upton

Australia’s legal system exonerated Lindy Chamberlain of infanticide this week, again, 32 years after a dingo ran off with her baby. A basis of the prosecution was always the notion that dingoes don’t eat babies. Ergo, prosecutors argued, the mother’s nightmare story was fabricated to cover up her own hideous deed while camping at Uluru.

A dingo at Fraser Island, Queensland, where a four-year old girl was attacked in 2007, helping confirm that dingoes are capable of attacking kids. Flickr: ogwen

Perhaps Chamberlain’s legal nightmare could have been avoided if the powers that be had listened more closely to the Pitjantjatjara people. The traditional stewards of the land where two-month old Azaria was hunted down know dingoes well. They reportedly never doubted that a dingo was capable of such ferocity. Similar attacks since have shown they were right.

The seclusive canines remain a mystery to most people. Scientists cannot even agree on whether the predators should be considered a native species in Australia. That’s because they were introduced several thousand years ago by seafarers sweeping south through Asia.

Those who argue that dingoes are a native species point out that they have struck an ecological balance with the environment.

University of New South Wales researchers set up a test they thought would reveal whether dingoes should be considered native. They monitored the activity of rabbit-like bandicoots in suburban backyards, some of which were home to pet dogs and some of which were not. Because the nocturnal bandicoots avoided yards that contained dogs during the day, they concluded that the creatures have evolved to instinctively identify the threat posed by dogs through thousands of years of dingo interactions. That suggests to them that dingoes have become a native species.

“The logical criterion for determining native status of a long-term alien species must be once its native enemies are no longer naïve,” the scientists, Alexandra Carthey and Peter Banks, wrote in a January paper published in the journal PLoS ONE. “Our study suggests that these bandicoots may no longer be naïve towards dogs.”

On the other hand, the foreign and invasive nature of the species in Australia is also clear.

When dingoes arrived, they did what invasive predators do best: They chewed through the wildlife and condemned native species to extinction. Their arrival coincided with the extirpation from mainland Australia of the thylacine, a dog-like predator that’s better known as the Tasmanian Tiger. The species survived in Tasmania, an island that remained inaccessible to the dingoes, until the 20th century when the last sad specimen died in a zoo.

Thylacines were Australia’s largest predators until the dingoes arrived. Recent research by scientists at the University of New South Wales and the University of Sydney revealed that the female thylacines of mainland Australia were considerably smaller than the dingos, making them vulnerable to direct predation by the continent crashers.

The dueling species also differed in a way that highlights dingoes’ alienness. Like almost all other native Australian mammals, thylacines were marsupials. (The other native Australian mammals are monotremes — egg-laying echidnas and platypuses.) Marsupials give birth shortly after conception and rear their young on a teat in a pouch. Dingoes, on the other hand, are placental mammals. If dingoes are to be considered a native species, then they are the continent’s only native placental mammal.

Dingoes can be found nowhere in the world other than in Australia. They have evolved into a distinct subspecies of the grey wolf, although that distinction is blurred by interbreeding with pet and feral dogs brought by more recent European settlement.

So if dingoes aren’t native to Australia, then they can be considered native to nowhere. They are either a native Australian species or a homeless wolf on a milleniums-long walkabout.

Either of which sounds like an appropriate description to me.

Uluru, a famous sandstone rock in the Northern Territory where baby Azaria was snatched in 1980 / Flickr: LKEM