Tuesday, September 30, 2008

The Ground-Breaking Research Must Be Included Here


Artist: Michael Skrepnick 2005.

Jan. 19, 2005

Relatives of Living Ducks and Chickens Existed Alongside Dinosaurs More Than 65 Million Years Ago


A reconstruction by well-known dinosaur artist Michael Skrepnick shows Vegavis in the immediate foreground with a duckbill dinosaur (hadrosaur) in the background.
A reconstruction by well-known dinosaur artist Michael Skrepnick shows Vegavis in the immediate foreground with a duckbill dinosaur (hadrosaur) in the background. Copyright Michael Skrepnick 2005.

Newly published North Carolina State University research into the evolution of birds shows the first definitive fossil proof linking close relatives of living birds to a time when dinosaurs roamed the earth.

Research by paleontologist Dr. Julia A. Clarke, an assistant professor in the marine, earth and atmospheric sciences department at NC State, and colleagues provides unprecedented fossil proof that some close cousins to living bird species coexisted with dinosaurs more than 65 million years ago. Information from a new avian species called Vegavis iaai indicates that these birds lived in the Cretaceous period and must have survived the Cretaceous/Tertiary (K/T) mass extinction event that included the disappearance of all other dinosaurs.

Analysis of fresh evidence from computed tomography (CT) scans of the fossil – which uncovered new bones deep within the rock matrix – and recovery of latex peels made of the specimen just after its discovery in Antarctica in 1992 revealed its importance to avian evolution and that it represented a new species. This partial skeleton is the most complete specimen from the Cretaceous to be found to have its evolutionary relationship to a living bird group. These new data show Vegavis is within the group Anseriformes, which includes ducks and geese.

The research is published in the Jan. 20 edition of the scientific journal Nature.
One half of the Vegavis iaai specimen (left) and the volumetric rendering from the computed tomography (CT) data (right).



The question of whether relatives of living birds existed alongside non-bird dinosaurs has evoked intense recent controversy in scientific circles. Some scholars, arguing from some “molecular clock” models and new DNA sequence data as well as the distribution of living bird groups, have concluded that relatives of living birds must have existed alongside non-avian dinosaurs and survived the mass extinction of dinosaurs at the K/T boundary, about 65 million years ago. Until the discovery of Vegavis, fossil data to support this hypothesis was weak at best.

Other scientists have claimed this limited previous data was unreliable and that the fossil record showed no evidence of living bird lineages in the Cretaceous. In a “big bang” theory of bird evolution, these scientists have proposed that relatives of today’s birds came on the scene only after non-avian dinosaurs became extinct at the K/T boundary.

“We have more data than ever to propose at least the beginnings of the radiation of all living birds in the Cretaceous,” Clarke says. “We now know that duck and chicken relatives coexisted with non-avian dinosaurs. This does not mean that today’s chicken and duck species lived with non-avian dinosaurs, but that the evolutionary lineages leading to today’s duck and chicken species did.”

The fossil’s fragility – the specimen was damaged as it was being prepared for study – led to difficulties in conducting a full examination in 1992. Earlier this year, Clarke received a grant from the National Science Foundation to give the fossil – named for the location it was discovered (Vega Island in western Antarctica) and for the name of the party that made the discovery (the Instituto Ant├írtico Argentino, or IAA) – a second look with a team of colleagues from Argentina and the United States.

Clarke and her fellow scientists conducted new analyses on the fragile partial skeleton. CT scans were performed on the fossil for the first time; these X-rays uncovered new bones in the rock matrix, including a number of vertebrae, pelvic bones, and arm and leg bones. The researchers also found the original latex peels – applied to the fossil before any other preparation had been done – that provided a mirror image of the bones originally exposed on the rock surface.

The newly discovered bones and latex peels allowed the scientists to compare features of Vegavis to other birds and determine its evolutionary relationships. Clarke and her colleagues used some of the largest data sets available and all placed Vegavis within the radiation of living birds – as most closely related to ducks and geese. Histological analysis of the bone tissues present in a cross section of a Vegavis arm bone not only indicates that Vegavis was an adult at the time of death but also supports inference of its evolutionary relationships from the independent phylogenetic results.

The data place Vegavis within Aves, which includes common ancestors of all living birds we have today and all its descendents – that is, the radiation of all living birds – and specifically within one group of Aves called Anseriformes, the waterfowl, which includes ducks, geese and allies. Within this group Vegavis is positioned close to the lineage leading to true ducks and geese, called Anatidae.

Clarke will now continue her search for more clues to the evolution of birds. “Looking to the Cretaceous for more parts of extant avian radiation is essential,” she says.

Funding for the research came from an NSF Office of Polar Programs Small Grant for Experimental Research.

- kulikowski -

An abstract of the Nature paper follows.

“Definitive Fossil Evidence for the Extant Avian Radiation in the Cretaceous”
Authors: Julia A. Clarke, North Carolina State University; Claudia P. Tambussi, Museo de la Plata-Conicet, La Plata, Argentina; Jorge I. Noriega, Centro de Investigaciones Cientificas y TTP-Conicet, Entre Rios, Argentina; Gregory M. Erickson, Florida State University; Richard A. Ketcham, University of Texas
Published: Jan. 20, 2005, in Nature
Abstract: Long-standing controversy surrounds the question of whether living bird lineages emerged after non-avian dinosaur extinction at the Cretaceous/Tertiary (K/T) boundary or whether these lineages coexisted with other dinosaurs and passed through this mass extinction event. Inferences from biogeography and molecular sequence data project major avian lineages deep into the Cretaceous period, implying their “mass survival” at the K/T boundary. By contrast, it has been argued that the fossil record refutes this hypothesis, placing a “big bang” of avian radiation only after the end of the Cretaceous. However, other fossil data – fragmentary bones referred to extant bird lineages – have been considered inconclusive. These data have never been subjected to phylogenetic analysis. Here we identify a rare, partial skeleton from the Maastrichtian of Antarctica as the first Cretaceous fossil definitively placed within the extant bird radiation. Several phylogenetic analyses supported by independent histological data indicate that a new species, Vegavis iaai, is a part of Anseriformes (waterfowl) and is most closely related to Anatidae, which includes true ducks. A minimum of five divergences within Aves before the K/T boundary are inferred from the placement of Vegavis; at least duck, chicken and ratite bird relatives were coextant with non-avian dinosaurs.

Article and Abstract courtesy of NC University@
http://www.ncsu.edu/news/press_releases/05_01/015.htm

University News Services
newstips@ncsu.edu.

Image of the Day



Hesperornis was a large, up to about five-foot-tall, flightless seabird. It was equipped with sharp, pointed teeth and probably preyed on fish and squids underwater. Although it was incapable of flight, Hesperornis was a swift swimmer that could propel itself through the shallow coastal waters of the Pierre Sea with its powerful hind legs. Painting by Dan Varner.

Penguins-Origin and Expansion

Origin and expansion of penguins --

* Penguins (Spheniscidae)
o distribution centered in the southernmost part of the southern hemisphere
o almost certainly had an extensive Cretaceous distribution within Gondwanaland (Cracraft 1974)
o early Tertiary fossil faunas suggest the influence of intercontinental connections

Fossil Evidence for the Extant Avian Radiation in the Cretaceous -- Clarke et al. (2005) provide apparent evidence that cousins of living birds coexisted with dinosaurs more than 65 million years ago. Information from a new species called Vegavis iaai indicates that these birds lived in the Cretaceous and must have survived the Cretaceous/Tertiary (K/T) mass extinction event that included the disappearance of all other dinosaurs. Analysis of the fossil, discovered in Antarctica in 1992, revealed a new species in the group Anseriformes, which includes ducks and geese. The question of whether relatives of living birds co-existed with non-bird dinosaurs has evoked controversy. Some investigators, using “molecular clock” models and DNA sequence data as well as the distribution of living birds, have concluded that relatives of living birds must have existed alongside non-avian dinosaurs and survived the mass extinction of dinosaurs at the K/T boundary. Others believe such data are unreliable, that the fossil record shows no evidence of living bird lineages in the Cretaceous, and that relatives of today’s birds evolved after the K/T boundary.

“We have more data than ever to propose at least the beginnings of the radiation of all living birds in the Cretaceous,” Clarke says. “We now know that duck and chicken relatives coexisted with non-avian dinosaurs. This does not mean that today’s chicken and duck species lived with non-avian dinosaurs, but that the evolutionary lineages leading to today’s duck and chicken species did.”
Vegavis


Fossil record and phylogeny of ornithurine birds (ornithurine = bird-like, as opposed to sauriurine = reptile-like, e.g, Archaeopteryx).
Solid lines show geological ranges of taxa with first and last occurrences shown by squares.
Dashed lines show postulated phylogeny compiled from the literature (Slack et al. 2006).


Calibrating avian evolution -- Slack et al. (2006) described the earliest penguin fossils and analyzed complete mitochondrial genomes from an albatross, a petrel, and a loon. The penguin fossils were from a Paleocene (early Tertiary) formation just above a well-known Cretaceous/Tertiary boundary site. The fossils, in a new genus (Waimanu), provide a lower estimate of 61–62 Ma for the divergence between penguins and other birds and thus establish a reliable calibration point for avian evolution. Combining fossil calibration points, DNA sequences, maximum likelihood, and Bayesian analysis, the penguin calibrations imply a radiation of modern (crown group) birds in the Late Cretaceous. This includes a conservative estimate that modern sea and shorebird lineages diverged at least by the Late Cretaceous about 74 million years ago. It is clear that modern birds from at least the latest Cretaceous lived at the same time as archaic birds including Hesperornis, Ichthyornis, and the diverse Enantiornithiformes. Pterosaurs also coexisted with early birds. Additional fossils and molecular data are still required to help understand the role of biotic interactions in the evolution of Late Cretaceous birds and thus to test that the mechanisms of microevolution are sufficient to explain macroevolution

Classic problems in historical biogeography are where did penguins originate, and why are such mobile birds restricted to the Southern Hemisphere? Competing hypotheses posit they arose in tropical-warm temperate waters, species-diverse cool temperate regions, or in Gondwanaland 100mya when it was further north. To test these hypotheses, Baker et al. (2006) constructed a phylogeny of extant penguins from 5851bp of mitochondrial and nuclear DNA. Their analysis suggests that an Antarctic origin of extant taxa is highly likely, and that more derived taxa occur in lower latitudes. Molecular dating indicates that penguins originated about 71 million years ago (i.e., penguins and albatrosses shared a common ancestor approximately 71 mya) in Gondwanaland when it was further south and cooler (and Antarctica was still attached to Australia and South America, and New Zealand was still relatively close to the supercontinent). Moreover, extant taxa are inferred to have originated about 40 mya (Eocene) when Aptenodytes diverged as the basal lineage, and coincident with the extinction of the larger-bodied fossil taxa as global climate cooled. Baker et al. (2006) hypothesized that, as Antarctica became ice-encrusted, modern penguins expanded via the circumpolar current to oceanic islands within the Antarctic Convergence, and later to the southern continents. Thus, global cooling has had a major impact on penguin evolution, as it has on vertebrates generally. Penguins only reached cooler tropical waters in the Galapagos about 4 mya, and have not crossed the equatorial thermal barrier.

The demise of the larger-bodied putative stem-group taxa near the end of the Eocene about 40 mya coincides roughly with the origin of Antarctic-breeding extant taxa (Aptenodytes and Pygoscelis) in the crown-group, and with the beginning of a general cooling in global climate. This was also approximately when the fish-eating cetaceans evolved, and it has been hypothesized they may have out-competed these larger penguins which probably relied on the same food source. Two abrupt cooling periods resulting in the formation of large ice sheets in Antarctica are associated with the diversification of penguin taxa. The first cooling occurred about 34-25 mya, when Spheniscus, Eudyptes and Eudyptula diverged from the older Antarctic genera. These latter ancestral lineages may have dispersed northward by the newly formed circumpolar current, judging from the occurrence of a Eudyptula fossil in New Zealand about 24 mya. As surface waters in the Southern Oceans continued to cool towards the middle Miocene, and the flow of the circumpolar current around Antarctica intensified, another rapid climate transition, the middle miocene climate transition (MMCT) and subsequent increase in Antarctic ice volume occurred between 14 and 12 mya. The MMCT was accompanied by a second bout of cladogenesis that gave rise to multiple species of extant penguins distributed at even lower latitudes, including tips of southern continents. If this scenario is run backwards in the future, continued global warming might be expected to drive temperate-adapted species out of lower latitudes towards their ancestral distribution, possibly causing multiple extinctions of existing species.

Information courtesy of:
http://people.eku.edu/ritchisong/birdbiogeography1.htm#cretaceousduck

Monday, September 29, 2008

Image of the Day

Waikato Penguin Fossils



Slightly older document, but still valid information:


Fossilised penguin discovered in the Waikato

By: Dr Nichola Harcourt
In January 2006, the children of the Hamilton Junior Naturalist Club (JUNATs) discovered the fossilised remains of a penguin on the foreshore of the Te Waitere Inlet at Kawhia.

Penguins are the heroes of many children's books and videos, being known and loved throughout the world for their comical walk and distinctive coats. Emperor penguins are the largest living penguins, obtaining heights of 1.2m tall and weights of 20-40kg. However, there were once far larger penguins waddling across the earth. In January 2006, the children of the Hamilton Junior Naturalist Club (JUNATs) discovered the fossilised remains of a penguin on the foreshore of the Te Waitere Inlet at Kawhia. At first glance the fossilised bones resembled rusty iron, however, as luck would have it amateur archaeologist Chris Templer was present on the trip and immediately recognised that the fossil was in fact a penguin. Penguin fossil - JUNATs

The penguin skeleton is almost complete, though missing the skull, which makes it a very important scientific find as other penguin fossils consist of a few bones only. One of the difficulties with unearthing a fossil on a muddy foreshore is that it can be rapidly covered by mud deposits from the incoming tide. Realising that the careful removal of the fossil would require forward planning, the JUNATs left the fossil in situ with the intention of returning at a later date with the appropriate tools. On their return, the JUNATs worked quickly to retrieve the fossil before it would be submerged by the incoming tide. The recovery involved cutting a trench in the rock and making a horizontal slice under the fossil. The fossil was then lifted out as a large embedded rock.

Having some experience in fossil stabilisation, Chris Templer removed residual debris from around the bones and coated the exposed bone surfaces with diluted polyvinyl acetate. The penguin fossil was placed in a custom-built cradle and anchored in place using a plaster mold. The fossil was then moved to the Waikato Museum and housed under controlled conditions. As it is anticipated that the fossil will undergo further rounds of preservation in the future, current stabilisation techniques are restricted to reversible methods. The fossil has been prepared for display and is now being exhibited in the foyer of the Waikato Museum.

We know from the structure and arrangement of the bones that the fossil is a penguin.

The key bones required for description and identification of the penguin include the wing bones, coracoid and tibiotarsus. The length of the femur is also a useful predictor for height of the bird. The straight shafts of the femur and humerus coincide with the genus Palaeeudyptes (as based on comparison with catalogued bones) while these bones are curved in other genera.

By comparing the length of the fossilised wing bone with that obtained from an adult Emperor penguin, we know that the fossil penguin was far larger. Comparing the length of the humerus, the fossilised penguin measures 180 mm, the Emperor's 128 mm, and the Little Blue penguin, 46 mm. It is not known why the early fossil penguins were so large, but may reflect their evolution in the absence of predators (which may have evolved somewhat later). This is based on the observation that the extinction of larger penguins coincides with the time that seals and smaller whales developed. This is the most complete fossilised penguin found yet to date. Therefore, it has the potential to solve many problems in understanding the evolution of fossil penguins. Given that all known penguins (living and fossilised) are found in the Southern Hemisphere, it is likely that penguins evolved there. New Zealand has an extensive fossil record of penguins with 13 species currently recognised.

Based on the established age of rocks in the Te Kuiti Group which are widespread in the Kawhia area, it is likely that the penguin would be aged in the range of 25-30 million years old. As a fossil of this antiquity lies well outside the sensitivity range of carbon dating, a rock specimen has been removed for further dating based on the foraminifera contained within. Two thirds of modern day New Zealand were submerged during the Oligocene. The movement of tectonic plates in the north of New Zealand caused large areas of the oceanic crust to be subducted, so that these areas were pushed into and over northern and western parts of the North Island. The Kawhia area was a series of small low-lying islands. Large marine species (e.g. sea urchins, oysters such as those found fossilised in limestone at Marokopa, molluscs and giant sharks) and giant penguins were abundant in the shallow seas.

Article courtesy of Waikato Museum @

http://www.waikatomuseum.co.nz/images/1645.jpg?w=267&h=200

Sunday, September 28, 2008

Antarctica - A Place Like No Other - Video

See this amazing 20minute video from the British Antarctic Survey
Here

Image of the Day



The leg bone (tarsometatarsus) of a fossil Penguin from Glen Massey, Waikato, North Island, New Zealand. It is of Early Oligocene age (34-27 million years old). Included in the photo is the equivalent bone from a Little Blue Penguin.

Wednesday, September 24, 2008

Tuesday, September 23, 2008

Image of the Day


Feathered Dinosaurs 3, originally uploaded by Aaron Gustafson.

Ancestor day. :)

Antarctic Protection



'Chemical equator' protects Antarctica's clean air


* 15:40 23 September 2008
* NewScientist.com news service
* Catherine Brahic


An invisible barrier separates the carbon-monoxide-rich air of South-East Asia from the pristine air of the Southern Ocean (Image: Hamilton et al./AGU)
An invisible barrier separates the carbon-monoxide-rich air of South-East Asia from the pristine air of the Southern Ocean (Image: Hamilton et al./AGU)Enlarge
Advertisement

Scientists have discovered a "chemical equator" just north of Australia that divides polluted air from South-East Asia from the largely uncontaminated atmosphere of the Southern Ocean that surrounds Antarctica.

The discovery will help researchers create accurate simulations of how pollutants move in the atmosphere and assess their impact on climate.

The polluted air of the northern hemisphere and the clearer air of the southern hemisphere tend not to mix. A mobile cloudy belt known as the Intertropical Convergence Zone that runs around the globe roughly at the level of the equator is thought to form a meteorological barrier between the two.

But a team of researchers have found an additional barrier high up above the Western Pacific that prevents the pollution from forest fires in countries such as Thailand and Sumatra contaminating the pristine skies above the Southern Ocean.

While flying a plane equipped to detect chemicals in the atmosphere, the team led by Jacqueline Hamilton of the University of York, UK, found a 50 kilometre wide "chemical line" north of Australia.
'Hidden' barrier

Levels of carbon monoxide – a by-product of burning – were four times higher to the north of the line than they were to the south.

At the time, the Intertropical Convergence Zone lay much further south, over Central Australia. So the researchers concluded that they must have come across another "hidden" barrier.

Hamilton explains that the shallow waters of the Western Pacific may help form the barrier.

The surface waters are amongst the hottest in the world, fuelling strong storm systems. "These powerful storms may act as pumps, lifting highly polluted air from the surface to high in the atmosphere where pollutants will remain longer and may have a global influence," she says.

To the south, cyclones above Australia suck in pristine maritime air. The two systems do not mix, creating an invisible chemical barrier.

Hamilton's study was carried out in January and February 2006, during the Australian-Indonesian monsoon, and the effect may be seasonal, she says.

Journal reference: Journal of Geophysical Research - Atmospheres (DOI: 10.1029/2008JD009940)

Original story HERE

Monday, September 22, 2008

Saturday, September 20, 2008

Thursday, September 18, 2008

Image of the Day


Prodigious Penguins, originally uploaded by pwallroth.

I don't think we'd have so many touristas in Antarctica with a beak like that. :)

Tuesday, September 16, 2008

Image of the Day


Feathered Dinosaurs 1, originally uploaded by Aaron Gustafson.

Something old-something new. :)

Check out these videos!

Dino Birds: Relating birds and dinosaurs:

http://videos.howstuffworks.com/hsw/21401-dinobirds-relating-birds-and-dinosaurs-video.htm

and also:












Wednesday, September 10, 2008

A Press Release from the Center for Biological Diversity







For Immediate Release, Monday, September 8, 2008

Contact: Shaye Wolf, Center for Biological Diversity, (415) 436-9682 x 301, cell (415) 385-5746

Penguins Marching Toward Endangered Species Act Protection;
Court Deadline Set For 10 Penguin Species Threatened By Global Warming

SAN FRANCISCO— A federal judge today approved a settlement between the Center for Biological Diversity and the U.S. Fish and Wildlife Service over the fate of 10 penguin species imperiled by global warming. Under the settlement, the Service must by December 19th complete its overdue finding on whether the penguins should be protected under the Endangered Species Act.

The finding is due on the emperor, southern rockhopper, northern rockhopper, Fiordland crested, erect-crested, macaroni, white-flippered, yellow-eyed, African, and Humboldt penguins.
“Right now penguins are marching towards extinction due to the impacts of global warming,” said Shaye Wolf, a seabird biologist with the Center for Biological Diversity. “Protecting penguins under the Endangered Species Act is an essential step toward saving them.”

Abnormally warm ocean temperatures and diminished sea ice have wreaked havoc on the penguins’ foods supply. Less food has led to population declines in penguin species ranging from the southern rockhopper and Humboldt penguins of the islands off South America, and the African penguin in southern Africa, to the emperor penguin in Antarctica. The ocean conditions causing these declines have been linked by scientists to global warming and are projected to intensify in the coming decades.

Krill, an essential food source not just for penguins but also for whales and seals, has declined by as much as 80 percent since the 1970s over large areas of the Southern Ocean. Scientists have linked the ocean conditions causing these declines to global warming and loss of sea ice. The emperor penguin colony at Pointe Geologie, featured in the film “ March of the Penguins,” has declined by more than 50 percent due to global warming.

Many penguin species also are harmed by industrial fisheries, either directly, such as when individual penguins are caught and killed in trawls, nets and longlines; or indirectly through the depletion of essential prey species such as anchovy and krill. Overfishing by industrial fishing fleets plays a prominent role in the hit movie “Happy Feet,” which features two of the petitioned species, the emperor and rockhopper penguins.

Listing under the Endangered Species Act will provide broad protection to these penguins, including a requirement that federal agencies ensure that any action carried out, authorized, or funded by the U.S. government will not “jeopardize the continued existence” of the penguin species. For example, if penguins are listed, future approval of fishing permits for U.S.-flagged vessels operating on the high seas would require analysis and minimization of impacts on the listed penguins. The Act also has an important role to play in reducing greenhouse gas pollution by compelling federal agencies to look at the impact of the emissions generated by their activities on listed species and to adopt solutions to reduce them.

The Center for Biological Diversity filed a petition in November 2006 to list 12 penguin species as threatened or endangered. The filing of the listing petition triggered a three-stage process for the Fish and Wildlife Service, with a strict timeline for each step. The agency is required to first decide within three months whether to conduct a status review of the penguins based on the concerns raised in the petition. The Service initiated status reviews of 10 of 12 penguin species, but it did not do so until July 2007, taking more than twice the time allowed under the law.

In the second stage of the listing process, the Service must decide whether the species should be listed for protection under the Endangered Species Act. This decision is required within 12 months of receiving the petition. In response to ongoing delays by the Service, the Center filed a lawsuit in February to set a court-ordered timeline for the listing decisions. Today’s court settlement ensures that the Service must make the listing determination by December 19th. A positive decision will then trigger the third stage, during which the agency has another 12 months to finalize the listing of the penguins. Until this process is completed, the penguins do not receive any protection under the Endangered Species Act.

“Penguin populations are in jeopardy and we can’t afford to delay protections,” Wolf said. “It is not too late to save them, but they need the lifeline provided by the Endangered Species Act and immediate reductions in greenhouse gas pollution.”

For more information on penguins and a link to the federal petition, please see:

http://www.biologicaldiversity.org/species/birds/penguins/index.html

The Center for Biological Diversity is a national nonprofit conservation organization with more than 180,000 members and online activists dedicated to the protection of endangered species and wild places.
# # #


________________________________________

Tuesday, September 9, 2008

Live from the Poles: Focus on Penguins

Safeguarding Fragile Antarctic Ecosystems

Although not directly related to Penguin Science, there are some very interesting proposals raised that are important enough to warrant a mention here. Those proposals deal with the conservation and survival of penguins through safeguarding measures. This is a lengthy article, but a necessary one for all who seek to preserve the lives of these birds.






New Rules Needed To Govern World's Fragile Polar Regions

ScienceDaily (Sep. 8, 2008) — A new co-ordinated international set of rules to govern commercial and research activities in both of Earth's polar regions is urgently needed to reflect new environmental realities and to temper pressure building on these highly fragile ecosystems, according to several of the experts convening in Iceland for a UN-affiliated conference marking the International Polar Year.

Please go here to read the rest of the article:

http://www.sciencedaily.com/releases/2008/09/080907123702.htm


Monday, September 8, 2008

Theory of Evolution of Flightless Birds Challenged


Long-held Assumptions Of Flightless Bird Evolution Challenged By New Research

ScienceDaily (Sep. 7, 2008) — Large flightless birds of the southern continents – African ostriches, Australian emus and cassowaries, South American rheas and the New Zealand kiwi – do not share a common flightless ancestor as once believed.

Instead, each species individually lost its flight after diverging from ancestors that did have the ability to fly, according to new research conducted in part by University of Florida zoology professor Edward Braun.

The new research, which appears this week in the online edition of the Proceedings of the National Academy of Sciences, has several important implications.

First, it means some ratites, like the emus, are much more closely related to their airborne cousins, the tinamous, than they are to other ratites, Braun said.

Second, it means the ratites are products of parallel evolution – different species in significantly different environments following the exact same evolutionary course.

Braun and his fellow researchers began closely studying this group of flightless birds, known collectively as ratites, after a discovery made while working on a larger-scale effort to better understand the evolution of birds and their genomes by analyzing corresponding genetic material sampled from the tissue of many different bird species and determining how they relate to one another.

As they analyzed the genetic material, they noticed that the ratites did not form a natural group based on their genetic makeup. Rather, they belonged to multiple related but distinct groups that contained another group of birds, the tinamous, with the ability to fly.

Previously, the ratites were used as a textbook example of vicariance, a term that describes the geographical division of a single species, resulting in two or more very similar sub-groups that can then undergo further evolutionary change and eventually become very distinct from one another.

Scientists assumed that a single flightless common ancestor of the ratites lived on the supercontinent of Gondwana, which slowly broke up into Africa, South America, Australia and New Zealand; once divided, the ancestor species evolved slightly in each new location to produce the differences among the present-day ratites, Braun said.

But in light of this new information, he said it's more likely that the ratites' ancestors distributed themselves among the southern continents after the breakup of Gondwana, which began about 167 million years ago, in a much more obvious way.

They flew.

Although these new revelations teach evolutionary scientists a great deal, they also pose a great many new questions. For example, why did these birds evolve into such similar organisms in such different environments?

"To know for sure, we'll have to go into the lab and really study the genetics underlying the ratites' developmental pathway," Braun said. "But nobody would have asked that question without the type of data we've collected, which raises the question in the first place."

The scientists' effort to analyze such a tremendous amount of genetic material collected from birds across the globe is in turn just a single part of a program called Assembling the Tree of Life, funded and organized by the National Science Foundation, which aims to assemble a body of similar research for every group of organisms on the planet, including animals, plants, fungi, algae and bacteria.


University of Florida. "Long-held Assumptions Of Flightless Bird Evolution Challenged By New Research." ScienceDaily 7 September 2008. 8 September 2008 /releases/2008/09/080903172152.htm>.


Tuesday, September 2, 2008

Timing is Everything for Krill Reproduction

From the Australian Antarctic Division:

Sea ice algae put spring in krill growth

Researchers have found that spring-time growth of sea ice algae is critical to krill growth and reproductive potential.

A krill larva at the final larval stage - Fucilia VI - just before moulting to become a juvenile krill
A krill larva at the final larval stage - Fucilia VI - just before moulting to become a juvenile krill
Photo: So Kawaguchi
The annual formation and retreat of sea ice around Antarctica is one of the largest physical changes on Earth. Besides its substantial impact on both regional and global climate, the ice cover plays a pivotal role in the biogeochemical cycles of the Southern Ocean and is an important structural element of Antarctic marine ecosystems. Forming a centimetre- to metre-thick skin on the ocean's surface, sea ice provides a platform for marine birds and mammals and a substrate for microalgae. It is also a habitat for Antarctic krill – a key species in the Southern Ocean food chain - that feed on ice algae during winter and spring, when food in the water column is scarce.

The importance of sea ice for marine ecological and biogeochemical processes is still poorly understood and information on the physical, chemical and biological properties of sea ice during winter and early spring is scarce. Classical ice sampling methods – often based on ice corers with small diameters – provide insufficient data to understand large-scale processes. New methods and technologies are needed to answer two important and pressing questions: how does the winter sea-ice extent affect biological productivity off East Antarctica and; how sensitive are krill populations to potential future changes in sea ice extent?

During the Sea Ice Physics and Ecosystem eXperiment (SIPEX) we used newly developed sampling and observing systems and technologies to address these questions. These included an instrumented Remotely Operated Vehicle (ROV) equipped with a sonar, light sensors and camera system, to observe and film krill under sea ice, and a custom-built Surface and Under Ice Trawl (SUIT) and Rectangular Midwater Trawl to collect animals for physiological experiments.

Scientists deploy the Remotely Operated Vehicle
Scientists deploy the Remotely Operated Vehicle
Photo: Klaus Meiners
The ROV was piloted from a control stand within a laboratory container on board the Aurora Australis, while a small crew operated its 350 m-long tether at a drill-hole out on the ice floe. Using online sonar data, the ROV could be 'flown' at a known distance to the subsurface of the ice, and while video observations were performed, measurements of the under-ice light field were taken. These optical measurements are used to estimate the algal biomass within the sea ice. The method allows the quantification of ice algal biomass along transects and is approximately 20 times faster than classical ice coring methods, saving valuable ship time.

The SUIT – developed by the Dutch research team of Dr. Jan van Franeker at Wageningen Institute for Marine Resources and Ecosystem Studies – floats directly under the ice and catches krill that are feeding at the subsurface of the ice floes. The deployment of this truck-sized trawl requires the coordination of ship officers on the bridge, winch operators, and gear officers and crew on the trawl deck. After demanding trials both in open water and thin ice, the trawl was successfully used in the inner pack, allowing us to catch krill from directly under the ice. Captured krill were then assessed for their feeding conditions. Experiments on krill growth rates and their demographic measurements were also conducted.

The Surface and Under Ice Trawl is equipped with a high-resolution video system to film the subsurface of the sea ice
The Surface and Under Ice Trawl is equipped with a high-resolution video system to film the subsurface of the sea ice
Photo: Patti Virtue
We found that adult krill were just about to start boosting their maturity in preparation for summer reproduction, by utilising ice algae under ice floes as a food source, as well as phytoplankton blooms in areas where the ice had started to retreat. During the voyage krill larvae were also found to be on the verge of accelerating their growth rates, in preparation for summer.

Undoubtedly, the amount and timing of algae associated with sea ice, and in open water at retreating ice edges, are very important determinants for krill population dynamics. Preliminary analysis of the data suggests that SIPEX was carried out at the very moment when biological activities were taking off in our survey area off East Antarctica. New methods were successfully deployed and tested and will allow time- and cost-effective sampling and monitoring of the sea ice habitat in the future.

The collected information on the physical, chemical and biological parameters of sea ice, in combination with our work on krill, will allow us to relate the performance of krill with various sea ice conditions and habitats during spring, and to help forecast what might happen to krill populations given possible future changes in sea ice extent.


http://www.aad.gov.au/default.asp?casid=35225

KLAUS MEINERS1 and SO KAWAGUCHI2
1Antarctic Marine Ecosystems program, ACE CRC
2Southern Ocean Ecosystems program, AAD