Pleistocene Saiga Antelopes

August 31, 2017

The saiga antelope (Saiga tatarica) ranged from western Europe to Alaska and the Yukon during some climate phases of the late Pleistocene.  This range closely corresponds with an environment known as the mammoth steppe.  This paleoenvironment was similar to the present day central Asian steppe but was more productive, hosting a greater variety of plants and microhabitats that included scrub, woodland, and wetland embedded in a sea of grass.  Summers were cool, winters were long, wind was constant, and precipitation was infrequent.  The bulbous nose of the saiga antelope is an adaptation for living in this kind of environment.  It helps warm frigid air and filter the dust in a dry windy climate.  The range of the saiga antelope has been greatly reduced since the late Pleistocene due to changes in the environment and overhunting by man.  Nevertheless, saiga antelope occurred in eastern Europe as late as the 17th century, indicating they are not a relict species confined to steppe grasslands.  A recent scientific study examining the bone chemistry of subfossil and extant saiga antelope specimens concluded this species can survive on a greater variety of plant foods than present day populations consume.

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Saiga antelopes are critically endangered today but lived from the British Isles to the Yukon, Canada during the late Pleistocene.

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Present day saiga antelope range.  During the Pleistocene they occurred from western Europe to Alaska.

This study found the diet of the saiga antelope overlapped with that of the caribou (Rangifer sp.) in southwestern Europe between 20,000 years BP-15,000 years BP.  It seems likely both species were subsisting upon lichen during winters when other plant foods were scarce.  Pleistocene saiga antelope apparently had a greater flexibility in their diet than present day populations.  The authors of this study suggest saiga antelope could potentially be introduced outside their present day range.  Poaching and disease outbreaks are endangering the surviving remnants of saiga antelope populations, so it could prove beneficial to establish new populations outside their present day range.  However, it’s possible some Pleistocene populations of saiga antelope may have been a distinct now extinct species with different dietary tolerances.  Some Russian paleontologist noted some morphological differences in saiga antelope specimens found outside their present day range, and they proposed a new species–Saiga borealis. Other paleontologists don’t accept this designation.  So far, no genetic studies have solved this difference of opinion.

The saiga antelope is considered a distant sister clade to the springbok-gerenuk clade.  They are the sole survivors of antelopes that roamed Europe before Ice Ages began to occur.  None of their closest relatives were able to evolve fast enough to survive deteriorating climatic conditions.

Reference:

Jurgensen, J.; at. al.

“Diet and Habitat of the Saiga Antelope during the Late Quaternary Using Stable Carbon and Nitrogene Isotope Ratios”

Quaternary Science Review March 2017

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The Korean Demilitarized Zone is an Amazing Wilderness

August 26, 2017

North Korea is not going to attack the U.S., no matter what Donald Trump says or doesn’t say.  The little fat turd who controls North Korea knows it would mean the end for him because even China wouldn’t back him, if he was the aggressor.  And the U.S. isn’t going to attack North Korea.  Trump will listen to his generals when they tell him an attack on North Korea would draw China into the war, and China has hundreds of nuclear weapons and enough surface-to-surface missiles to sink our entire Pacific fleet.

I feel sorry for the North Korean people because they are forced to live under the little fat turd’s rule.  But the U.S. voluntarily elected a giant fat turd as president.  Actually, referring to Donald Trump as a turd is an insult to turds.  A turd in a punchbowl would make a better president than Trump.

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A turd in a punch bowl would make a better president than Donald Trump.

Trump opened up his presidential campaign by calling Mexicans “drug dealers and rapists”–words that sounded like they came straight out of Archie Bunker’s mouth.  Ironically, Trump must think rape is only bad if a Mexican is the rapist because Trump brags about how he can rape women and get away with it. Trump is so dumb he equates peaceful protestors with neo-Nazis, and he thinks Jefferson Davis and other Confederate figures are comparable to George Washington and Thomas Jefferson.  They are not the same–they are the opposite.  George Washington helped found this country, while the Confederacy tried to tear it apart.  The Confederacy was an enemy of the U.S..  Enemies of the U.S. should not be venerated.  Trump has no credibility because he rarely tells the truth about anything.  He makes up absurd conspiracies and tweets them out in the middle of the night.  This is the symptom of a man who doesn’t have all his marbles.  Trump is also highly unethical, but I’m not going  to delve into this here because just the details of his crooked business interests could fill volumes.

Trump disgusts me, but I am even more disgusted with the stupid uneducated fools who voted for him.  They all look like a bunch of angry, shriveled-up losers.  They are so dumb they actually think this billionaire prick gives a shit about them.  Trump’s economic policies, if he ever is able to enact them, would greatly aid ultra rich plutocrats, like himself, while steamrolling the working class chumps who voted for him.  Trump proved this when he said he would actively work to make Obamacare fail.  This means he cares more about a legislative victory than the well being of the American people.  The election of Trump is an insult to the intelligence and integrity of the American people.  I think many people voted for him because of name recognition.  They were familiar with this dumb bigoted celebrity from his brainless TV show.  Other people are attracted to his xenophobic racism.  It is disturbing to realize there are millions of pro-rape racists living in this country.  I hate Trump voters.

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Trump supporters are shriveled up old losers.  His rallies are a sea of white faces, though occasionally there will be a token black guy carrying an awkward sign saying “Blacks for Trump.”  The Trump campaign undoubtedly paid for the token black guy to stand there.  Trump was elected by pissed off racists.  It is alarming to realize there are tens of millions of brain dead racists in this country.

The Korean Demilitarized Zone divides North and South Korea.  People haven’t lived in this zone for 64 years, and the land has reverted to wilderness.  The KDZ is 400 square miles of mountains, forests, prairies, wetlands, and tidal marshes.  At least 52 species of mammals live in the KDZ including 5 kinds of deer, wild boar, Asiatic black bears, leopards, leopard cats, and raccoon dogs.  Many of the species that live here are rare or extinct in the rest of Asia.  Critically endangered long-tailed gorals (a kind of goat), musk deer, red-crowned cranes, white-naped cranes, and black-faced spoonbills make the KDZ their home.  There are even rumors of Siberian tigers roaming the KDZ.  It seems impossible that so much wildlife can exist here.  Reportedly, there are 2500 landmines per square mile, and animals occasionally do trigger them.  Animals can thrive in minefields but can’t tolerate the presence of man–another example of how detrimental people are for wildlife.  Maybe some day, if Korea is ever unified, the KDZ will become a park.  In the rest of China and Korea wildlife has been obliterated, and pollution is a disaster.  Asia badly needs a park like this.

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The critically endangered red-crowned crane finds refuge in the KDZ.

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Ruddy kingfisher.

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Korean water deer.

Naemorhedus caudatus

Long-tailed goral.

 

Rapid Anole (Anolis carolinensis) Evolution

August 21, 2017

Misinformed creationists some times ask, if evolution is true, why isn’t it happening now?  There is a simple answer to that question.  Evolution is an ongoing process, and it IS happening now.  Evidence of continuing evolution isn’t readily apparent to the non-observant eye because usually it is a slow process–evolution often requires generations of natural selection to influence the phenotypical changes that demonstrate it.  However,  scientists discovered an example of evolution that occurred within 1 generation of an anole population in south Texas.  A team of scientists had recently studied the differences in cold tolerance between the population of anoles that live in south Texas with those that live near the northern limits of their range.  The south Texas anoles lose muscular coordination when temperatures drop to about 51 degrees F, while anoles near the northern limits of their range lose coordination when temperatures reach 43 degrees F.  An unusual cold snap struck south Texas shortly after scientists gathered this data, and they took another look at this anole population.  They discovered that exposure to cold temperatures changed the DNA of south Texas anoles.  4 genomic regions, especially those related to nervous system function, changed.  The lizards had rapidly evolved the ability to retain muscle coordination at lower temperatures, and they will pass these genetic changes on to the next generation.  This is a perfect example of evolution, defined as the change over time in the genetic characteristics of a population.  Most creationists can’t even define evolution.  They reject the fundamental basis of all biological science because it interferes with their belief in the supernatural.  Let’s see them try to deny this case study.

Anole characteristic threat display.

Anoles are a successful and rapidly evolving species. Some populations have adapted to city living, having evolved stickier toe pads that enable them to climb window glass.  In Florida the brown Cuban anole was accidentally introduced.  They occupy the same niche as the American anole.  In areas colonized by this alien anole, native anoles evolved larger toes that allow them to climb thinner branches.  This occurred in less than 15 years (20 generations for anoles living in Florida).  So now, areas with both species of anoles have a niche partition–Cuban anoles occupy lower branches, while native anoles live in the tree tops.

Worldwide, there are 391 species of anoles, but 9 are closely related to the species (A. carolinensis) that is widespread in the southeastern U.S.  Genetic studies suggests all 9 of these species descend from a founder population originating on Cuba.  A. carolinensis diverged from western Cuban anoles about 6 million years ago.  This occurred as a rafting event when a tropical storm washed debris from Cuba to the Gulf Coast of North America.  At least 1 male and 1 female were clinging to the debris when it made landfall.  All Caribbean islands were populated by anoles originating on Cuba from similar rafting events.

Fossil evidence of anoles has been excavated from 1 site in Georgia (Ladds), 1 site in Alabama (Bell Cave), and 10 sites in Florida.  None date to older than the mid-Pleistocene, but genetic evidence indicates they’ve occurred in southeastern North America since the late Miocene.

References:

Campbell-Staten, Shane; et. al.

“Winter Storms Drive Rapid Phenotype, Regulation, and Genome Shift in the Green Anole Lizard”

Science August 4, 2017

Glor, Richard; J. Losos, A. Larso

“Out of Cuba: Overwater Dispersal and Speciation Among Lizards in the Anolis subgroup”

Molecular Ecology 14 2005

Extant South American Canids are Ancient Relics

August 16, 2017

Several species of medium-sized canids native to South America descend from species that formerly occupied North America.  The extant bush dog (Speothos vunaticus), maned wolf (Chrisocyon brachyuras), and the recently extinct Falkland Islands wolf (Dusicyon australis) are (or were) similar to primitive dogs that occurred across North America during the late Miocene and Pliocene.  The emergence of the Canis genus (wolves and coyotes) early during the Pleistocene competitively excluded these primitive dogs from North America, but their ancestors pushed through the jungles of Central America, and they colonized South America where they still thrive today when not persecuted by man. The tropical rain forests of Central America served as a geographical barrier that prevented Canis species from following their primitive relatives.  Though Canis species may be more adaptable overall, their primitive relatives were better able to withstand tropical conditions, a factor that saved them from extinction.

The South American bush dog is a widespread but uncommon pack-hunter that preys on large rodents, peccaries, and rheas.  One genetic study suggests they are most closely related to maned wolves, but another more recent genetic study determined they are most closely related to African hunting dogs.  A species similar to the African hunting dog lived in North America as late as the mid-Pleistocene, so the bush dog may very well be an offshoot of this canid line.  The maned wolf is a solitary species, not a pack-hunter–additional evidence supporting a closer evolutionary link between bush dogs and pack-hunting African dogs, rather than the maned wolf.  The bush dog was known from fossil evidence found in a Brazilian cave before it was recognized as an extant species.

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South American bush dogs.  They are descended from primitive dogs that roamed North America before the Canis genus dominated that continent.

The Falkland Islands wolf was the only mammal species native to the Falkland Islands.  It was a completely naïve species, unafraid of man, and was hunted to extinction by the late 19th century.  Settlers coveted its furry coat and were afraid it would kill their sheep.  Actually, the diet of this species is unknown, but it probably subsisted on penguins, geese, and sea shore scavenging.  How this species colonized the Falkland Islands, located 285 miles from the mainland of South America, was a mystery until recently.  Geologists discovered underwater ridges connected to the mainland that were above sea level during Ice Ages.  A narrow 20 mile straight between the ridges and the Falkland Islands froze into solid ice during winters of the Last Glacial Maximum (~16,000 years ago), allowing the canids to cross.  They may have been hunting penguins on the ice, leading them to the islands.  No other mammal found motivation to cross the ice bridge.

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Extinct Falkland Islands Wolf.  Unfortunately, they had no fear of people.

Genetic evidence suggests the Falkland Island and maned wolves are most closely related to false foxes (Lycalopex sp.), 6 species of which are found in South America today.  However, the Tibetan fox is the maned wolf’s closest living relative.  The Tibetan fox is likely related to the ancestors of all false foxes.  An extinct species of maned wolf (C. nearctus) lived in North America during the Pliocene.  Fossil evidence of this species has been found at sites in Arizona, California, and northern Mexico.  The maned wolf has long legs that help it look over tall grass for rodents–its main prey item.  Genetic evidence shows maned wolf populations increased during Ice Ages when grasslands expanded and contracted during interglacials.  Pliocene environments were often dry and included an expansion of prairie habitat, so it’s likely the North American maned wolf also had long legs.  The fossil evidence of C. nearctus is limited to lower jaws and teeth, so it’s not known how long its legs were.  Maned wolves are omnivorous, and they are important dispersers of seeds.  They often defecate on leafcutter ant nests, and the ants move the viable seeds, helping them germinate.

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Maned wolf.  Maned wolves lived in North America during the Pliocene.

The maned wolf grows to about 50 pounds, but a larger genus of primitive dogs lived in North America until the early Pleistocene.  Theriodictis hunted megafauna in Florida.  Species from the Canis genus outcompeted them in North America, but they continued to thrive in South America until the late Pleistocene extinctions of the megafauna.

Reference:

Nyakatura, K.; et. al.

“Updating the Evolutionary History of Carnivora (Mammalia): A New Species Level Super Tree Complete with Divergence Time Estimates”

BMC Biology 10 (12) 2017

Tedford, Richard; X. Wang, B. Taylor

“Phylogenetic Systematics of the North America Fossil Caninae”

Bulletin of the American Museum of Natural History 2009

 

Hurricane Ivan Uncovered a 60,000 year old Cypress Forest in the Gulf of Mexico

August 9, 2017

In 2004 Hurricane Ivan spawned 140 mph winds, 90 foot waves, and the fastest sea floor current ever recorded.  That incredible sea floor current removed a sediment layer covering a 60,000 year old cypress forest in the Gulf of Mexico.  The exposed trees formed a natural reef, attracting a concentration of fish and other sea life 60 feet below the ocean surface and 15 miles offshore.  Fishermen noticed the unusual concentration of fish and asked scuba divers to investigate.  The scuba divers discovered the uncovered ancient forest, and scientists are now studying this rare site.

The scientists who visited the flooded forest were impressed with the marine life they encountered–flounder, cardinal fish, red snapper, blennies, sea bass, moray eels, sandbar sharks, hawksbill turtles, octopus, boring worms, anemones, and sponges.  But they were even more impressed with the ancient cypress wood they brought with them to the surface.  They sawed through it in the laboratory and smelled fresh sap.  Nevertheless, they couldn’t use radiocarbon dating because they discovered the wood was over 50,000 years old–too old for that method.  Instead, they found the nearest organic material that could be dated and estimated a 60,000 year old date based on stratigraphic location and assumed rates of deposition.

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Map of weather stations in south Alabama.  During Ice Ages dry land extended for miles into the Gulf of Mexico.  Mobile Bay was a valley of forests and grasslands.  Dauphin Island and Fort Morgan were high hills “hundreds of feet above the surrounding landscape.”

When it was alive, this flooded forest stood during a time period classified as Marine Isotope Stage 3.  I am fascinated with MIS3 because the dramatically fluctuating climate cycles had a major impact on natural communities.  MIS3 occurred just before the Last Glacial Maximum (the coldest stage of the last Ice Age), but unlike the LGM, MIS3 experienced warm interstadials alternating with cold phases.  Many geographical regions hosted an admixture of northern flora and fauna with warm climate species of plants and animals because of this climatic instability.  Tree rings on the fossil cypress wood excavated from this locality demonstrate this instability.  The tree rings provide a 489 year record of climate from MIS3.  The cypress tree rings show climate varied with warm wet years and dry cold spells but for the most part they are narrower than tree rings found in modern day cypress trees.  This reflects a cooler drier climate with lower levels of carbon dioxide in the atmosphere.  The trees were especially stressed during the last 50 years of their existence, and they all died at the same time, though the trees were of different ages.  Saltwater intrusion killed the trees.

Sea level rose rapidly here, probably during a warm phase of climate when glaciers were melting.  Cypress wood is resistant to decay, an adaptation for living in aquatic environments, but when exposed to air will eventually rot away.  The dead stand of cypress wood likely stood for decades, perhaps a century, before becoming covered in sand and mud.  Thus sealed off from air, it was preserved for tens of thousands of years.  Now that it is exposed to oxygen again, it will decay into nothing in a few centuries.

Scientists cored into the mud around the trees and took samples of pollen to analyze the type of natural environment that existed here 60,000 years ago.  Cypress, oak, and alder pollen dominated.  The palynologist who analyzed the pollen composition (the data as far as I know is still unpublished) concluded the forest was a rare type that no longer occurs in the region.  The closest modern analogue is classified as an Atlantic Coastal Plain Blackwater Bar/Levee Forest.  This type of forest occurs in small areas near the coasts of North and South Carolina.  Bar/Levee forests grow on soil formed on the inside bend of a river.  Sediment accumulates here through deposition, and the area is seasonally flooded.  (Indeed, this particular forest occurred alongside a river, and the paleomeander scar is still visible at the bottom of the ocean adjacent to the flooded forest.)  Dominant trees in a Bar/Levee forest are cypress, river birch, laurel oak, overcup oak, willow oak, sweetgum, red maple, elm, and loblolly pine.  The understory consists of holly and hop hornbeam along with red maple and ash saplings.  The shrub layer is made up of blueberry, titi, sweetspire, grape, poison ivy, climbing hydrangea, Alabama supplejack, greenbrier, sweet pepperbush, violet, and sedge.  Spanish moss covers the trees.  Bar/levee forests are similar to bottomland hardwood forests but are distinguished by the abundant presence of river birch or water elm (Planara aquatica which is not a true elm).

Macrofossils of Atlantic white cedar and palm have also been found among the dead cypress.  There are small disjunct colonies of Atlantic white cedar scattered throughout the southeast, indicating it was more widespread in the region during the Ice Age.  (See: https://markgelbart.wordpress.com/2012/03/11/the-discontinuous-range-of-the-atlantic-white-cedar-chamaecyparis-thyoides/ ) The presence of palm shows that climate, though cooler than that of today, was still warm enough for that species.  I suspect this was a unique forest that doesn’t exactly match any classified natural community of the present day.

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60,000 years ago, a cypress and oak forest grew at a location 15 miles off the coast of Alabama.  It was rapidly inundated during a sudden rise in sea level, becoming covered in sediment before the cypress trees rotted away.

The pollen evidence suggests alder was a pioneer species here that probably became established when the point bar of the river began depositing sediment.  Cypress and oak became dominant for about 500 years.  Then, after salt water intrusion killed the cypress, grass pollen predominates, suggesting a salt marsh replaced the cypress forest.  Extinct megafauna such as mastodon, tapir, and capybara undoubtedly passed through this environment, but vertebrate fossils have yet to be found.

Below is a documentary about the flooded forest–the source of information for much of this blog entry.

Reference:

Schafale, M; and A. Weakley

“Classifications of the Natural Communities of North Carolina, third approximation”

North Carolina Natural Heritage Program 1990

The Enigmatic Small Wolf Species of the Early-Mid Pleistocene of North America

August 6, 2017

There were at least 5 species of wolf-sized canids living in North America from about ~1.8 million years BP-~300,000 years BP.  Edward’s wolf (Canis edwardii) was a medium-sized canid, averaging about 75 pounds, that apparently occurred from coast to coast.  It’s the same species formerly known as Canis priscolatrans, and it was an evolutionary dead end–its extinction occurred about 300,000 years ago.  Armbruster’s wolf (Canis armbrusteri) co-occurred with Edward’s wolf but was a larger species, weighing on average 125 pounds.  Armbruster’s wolf is thought to be the evolutionary ancestor of the famous dire wolf (Canis dirus) which became extinct about 11,000 years ago.  Troxell’s dog (Protocyon texanus) was related to African hunting dogs.  Fossil evidence of this species has been found in Texas, the Yukon, and Alaska; and it probably had a wider range than the fossil record indicates.  Perhaps it lived in low numbers in geographic regions where processes of preservation were rare. The timber wolf (Canis lupus) was apparently confined to Alaska and Eurasia during the mid-Pleistocene and didn’t colonize North America until the late Pleistocene.  Finally, a mystery species nearly identical to the present day coyote (Canis latrans) left fossil evidence at sites in Nebraska, Colorado, California, Arkansas, Pennsylvania, Maryland, and West Virginia.  Some of the fossils at these sites are estimated to be 1 million years old.  Paleontologists identified these specimens as Canis latrans, though they cautiously also referred to them as coyote-like.  However, a recent study of wolf, coyote, and dog genetics determined the coyote is a recently evolved species no older than 50,000 years when it first diverged from timber wolves.  This result suggests the mid-Pleistocene species identified as Canis latrans may be an extinct mystery species.

In addition to the fossil record scientists can use a molecular clock to determine when 2 or more species diverged from a common ancestor.  A species has a fixed mutation rate, and scientists add up generations of mutational changes to determine the time of divergence from its closest related species.  (This is a vastly oversimplified explanation but will suffice for the purpose of this blog article.)  There are problems with using molecular clocks.  Different species have different rates of mutation, and the mutation rate can change over time.  Scientists try to calibrate the molecular clock with the fossil record by using various statistical methods.  An early study of wolf and coyote genetics determined the 2 species diverged about 1 million years ago, and this result is consistent with the fossil record, but the results of the newer study mentioned above totally contradict the fossil evidence.  There are 2 explanations for this discrepancy.  a) The new study is wrong.  Maybe the scientists used too many assumptions and dodgy statistics and just came up with the wrong number.  or b) The new study is right, and the mid-Pleistocene species identified as Canis latrans was an evolutionary dead end that went extinct.  The similarity between this mystery species and Canis latrans is just a remarkable example of convergent evolution. c) The new study is right and is not inconsistent with the fossil record.  Perhaps the common ancestor of the coyote and timber wolf was coyote-like.  Ice Age glaciers caused the divergence.  Populations north of the Cordilleran ice sheet evolved into timber wolves but populations south of it remained coyote-like.

Below are images of mid-Pleistocene  skull and jaw specimens identified as Canis latrans along with the skull and jaw of a present day coyote.  I can’t tell the difference, so I favor explanation a.  Even in a case of convergent evolution, there would have to be some notable anatomical differences between 2 different species.

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Genetic evidence from 1 study suggests coyotes diverged from gray wolves about 50,000 years ago.  However, this skull, assigned to Canis latrans (coyote) from Maryland dates to >300,000 years ago.  Is the genetic evidence incorrect or was there a species then so similar to modern coyotes it deceived paleontologists? Image from the below referenced paper by Tedford et. al.

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Present day skulls of Canis latrans.

Some zoologists think coyotes and dogs should now be classified as subspecies of timber wolf based on the data from the newer genetics study.  I don’t agree.  The behavioral characteristics of wolves, dogs, and coyotes are too dissimilar; and they don’t normally interbreed in natural conditions.  Humans can easily eradicate wolves from a region, but they can not eliminate coyotes because the latter are so much better adapted for living close to people.  Wolves and coyotes can survive in the wilderness, but they make terrible pets.  Most dogs make excellent companions for people but can’t survive in the wild.  In my opinion wolves, coyotes, and dogs are closely related but definitely different species.

References:

Tedford, Richard; X. Wang, and B. Taylor

“Phylogenetic Systematics of the North American Fossil Caninae”

Bulletin of the American Museum of Natural History  2009

Von Holdt, Bridgett; et. al.

“Whole Genome Sequence Analysis Shows that Two Endemic Species of North American Wolf are Admixtures of Coyote and Gray Wolf”

Science Advances (27) July 2016

Wilson, Paul; et. al.

“DNA Profile of Eastern Canadian Wolf and Red Wolf Provide Evidence for a Common Evolutionary History Independent of the Gray Wolf”

Canadian Journal of Zoology 2000

 

 

 

Floodplain Fish

July 31, 2017

River systems host a hidden world of tiny invertebrates.  Some are microscopic, while others, though visible to the naked eye, remain unseen unless a curious fisherman cuts open the stomach of his catch.  A fish’s stomach might contain small crustaceans including water fleas (Cladocera), seed shrimp (Ostracada), amphipods, copepods and/or isopods.  These minute shrimp-like creatures form the basis of a food chain that supports fish populations.

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Seed shrimp (Ostracods) along with other small crustaceans are an important part of the food chain in aquatic habitats.

In southeastern North America rivers overflow their banks between November and March because cooler temperatures reduce evapotranspiration and dormant riverside vegetation takes in less water.  The flood stage is especially wide in the flat coastal plain region where a sheet of water 2-3 feet deep can cover hundreds of square miles alongside major rivers, though modern dams, ditches, and canals have reduced the former extent of these flooded wetlands.  This flooded land offers more territory for fish to forage and reproduce.  The diet of many fish species changes from the aquatic crustaceans mentioned above to prey that normally lives some distance from the river.  1 study found fish occupying floodplains ate a species of isopod that lives in small pools of water, terrestrial species of crayfish, beetle larva, and caterpillars.  These terrestrial species were not normally found in fish’s stomachs until the flood stage.  Some species of fish even breed over floodplains that become dry land during summer.  The blueback herring (Alosa aetivalis) spawns in flooded hardwood swamps, unlike its relatives the American shad and hickory shad that spawn in the main channel and tributaries of a river.  Blueback herring eggs adhere to twigs on the forest floor.

 

Blueback herring spawn over flooded land.

White bass (Morone chrysops) also spawn on floodplains during high water.  This species is probably the “white fish” mentioned by John Lawson in his book A New Voyage to the Carolinas.  A few years ago, I wrote a blog article identifying the fish Lawson wrote about in his early natural history book.  (See: https://markgelbart.wordpress.com/2014/08/31/identifying-the-species-of-fish-described-by-john-lawson-in-1710-part-2/   )I was able to figure the identity of most of them despite the archaic names and vague descriptions, but his “white fish” stumped me.  Zach Matthews, editor of The Itinerant Angler, suggested to me that Lawson was referring to the white bass.  Lawson’s description that it was found in “freshets” or floodwaters is good evidence he was discussing the white bass.

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White bass also spawn over floodplains.  This is probably the “white fish” John Lawson discussed in his book A New Voyage to the Carolinas.

There have been plenty of genetic studies of the white bass and its cousin the striped bass because the 2 closely related species are hybridized for sports fishermen.  But I can’t find any genetic studies that explore the evolutionary origin of this genus.  It seems likely white bass diverged from the same ancestor as the striped bass, and this common ancestor was probably an anadromous fish, like the latter species. The initial ancestral population of white bass began spawning on floodplains and became landlocked and unable to return to the ocean when something temporarily blocked access to the ocean.   This explains how the 2 species diverged from each other.  White bass evolved the ability to survive entirely in freshwater habitats and were able to colonize aquatic environments much further inland than striped bass.  White bass collect fat reserves and can endure cold winters.  They became well adapted to the colder temperatures of Pleistocene Ice Ages.  Geneticists could probably use a molecular clock to determine when this divergence occurred, and they may be able to tie the timing to some climatic event.

Fish use floodplains to migrate to new habitats and maintain genetic vigor between populations.  During flood stages many fish from the Okefenokee Swamp swim through flooded habitat to the Suwannee River.  Warmouth, flier, bowfin, pickerel, bullheads, and lake chubsuckers have all been recorded traveling through 2-3 feet of water to the river.  Floods can also connect breeding fish from oxbow lakes with fish from the main branch of the river.  Shiners, bream, catfish, darters, mosquito fish, and starhead minnows often travel through flood waters between oxbow lakes and rivers.  Eels also use these corridors but they don’t breed in freshwater.  Many fish get trapped in oxbow lakes and sloughs after floodwaters recede.  However, oxbow lakes provide better habitat for fish than rivers, often holding 12 X more fish per acre though species diversity is identical.  The most common fish in Altamaha River oxbow lakes are gizzard shad, spotted sucker fish, and channel catfish.

During Ice Ages rivers in the southeast didn’t flood as much as they do today.  The fish best adapted for braided river patterns were most common.  Cut-off channels within river beds probably held concentrated populations of catfish and killifish.  Anadromous fish such as shad and striped bass spawned in areas that have since been inundated by rising sea levels.  Following the end of the Ice Age, there was a supermeandering phase of rivers when flooding was more extreme than it is today.  This caused a resurgence of floodplain fish species.

Reference:

Clark, J.R.; and J. B. Forado

Wetlands of Bottomland Forests

Proceedings of Bottomland Hardwood Forest Wetlands in Southeastern United States 1980

The Younger Dryas Cold Phase may have been Exacerbated by Megafauna Extinctions

July 26, 2017

In my previous blog entry I explained how Pleistocene megafaunal extinction impacted ecosystems, but some scientists hypothesize the loss of megafauna influenced atmospheric conditions as well.  The existence of enormous ice caps during Ice Ages caused extremely unstable climate conditions as the below temperature graphs illustrate.  The climate alternated between warm phases known as Dansgaard-Oeschger Events and cold phases referred to as Heinrich Events.  The onset of these patterns was often sudden occurring within decades, though some cold phases occurred gradually.  The fluctuations were interrelated.  Dansgaard-Oeschger Events melted glaciers and eventually released too much cold fresh water into oceans, shutting down ocean currents that carried tropically heated water to northern latitudes.  Colder oceans caused temperatures on adjacent continental land masses to drop. The Younger Dryas, a cold phase that began 12,900 years ago, was an exaggerated Heinrich Event.  Scientists, led by F. A. Smith, a professor at New Mexico University, propose the collapse of megafauna populations in North and South America contributed to the severity of the Younger Dryas stadial.

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Ice core data from Antarctica illustrates fluctuations in climate over the past 500,000 years.  The brief but severe Younger Dryas cold snap can’t be seen on this chart, but supposedly it was an anomaly compared to other fluctuations.

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Ice core data from Greenland showing fluctuations in climate over the past 23,000 years.  Within decades a warming climate phase reversed, and average annual temperatures matched the coldest of the preceding Ice Age.

Large populations of megafauna produce immense quantities of manure–a source of methane (CH4), an important greenhouse gas.  Megafaunal populations collapsed shortly before the Younger Dryas began, so perhaps without the mitigating effect of this manure-sourced methane temperatures dropped further than they would have, if these animals had still been present in the environment.  Moreover, more forest replaced grasslands because there were no megaherbivores suppressing tree regeneration.  Trees help reduce CO2, another greenhouse gas.  Today, methane produced by increasing populations of livestock combined with deforestation contribute to an increase in greenhouse gas concentration and global warming.

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Modern day livestock contribute to greenhouse gas emissions.  A new hypothesis suggests the extinction of Pleistocene megafauna in North and South America contributed to the severity of the Younger Dryas cold phase when average annual temperatures suddenly plummeted to levels not seen since the Last Glacial Maximum.

Reference:

Smith, F.A.; S. M. Elliott and S.K. Lyons

“Methane Emissions from Extinct Megafauna”

Nature Geoscience 3 (6) 2010

 

The Unraveling of Pleistocene Ecosystems in Southeastern North America

July 23, 2017

The entrance of humans into southeastern North America and the subsequent extinction of megafauna species had a profound effect on the region’s ecosystems.  Evidence from other regions suggests megafauna populations began to collapse during the Boling/Alerod interstadial, a warm phase of climate following the Glacial Maximum that lasted from ~15,000 years BP-~12,900 years BP.  Megafauna populations should have been increasing during this climate phase because the increase in precipitation and warmer temperatures fostered greater plant growth and species composition diversity.  However, the improved climatic conditions benefitted people and in turn the presence of humans is almost always disastrous for wildlife.  When the men failed on a day’s hunting trip, they still had plenty of food, thanks to the women who gathered wild plant foods and trapped fish, turtles, and birds in their nets all day.  The increased precipitation also caused an expansion of wetland habitat and aquatic resources. Under these environmental conditions human populations rose rapidly, much to the detriment of large animals.  Within a few thousand years humans wiped out almost all of the large mammal species in the south, so for the first time since a few million years after the KT impact that knocked off the dinosaurs, the region was nearly devoid of large megafauna populations.

Few scientists have studied the details of megafauna extinctions in the south and how they impacted the ecosystem.  One study (Smith, F.A. 2015 referenced below)  looked at all the Pleistocene sub-fossils found in Hall’s Cave, Texas–a site with well dated chronology and a continuous record of mammals from 22,000 years BP to the present.  A statistical analysis suggests many Pleistocene mammals were positively associated with other species.  This means complex interrelationships between species probably existed, though we have no way of knowing what they were.  This blog entry is my attempt, as an educated layman, to imagine what occurred as Pleistocene ecosystems unraveled.

I propose the first animals to be overhunted to extinction in the southeast were ground sloths, pampatheres, glyptodonts, and giant tortoises.  Ground sloths and pampatheres were important keystone species because they constructed extensive deep burrow systems.  (I also believe giant tortoises, like their extant relative the gopher tortoises, dug burrows.  Unfortunately, a paleontologist labeled giant tortoises as “non-burrowing” in a 1950’s era paper, and no qualified vertebrate zoologist has ever challenged his assumption.  I am unaware of any study of Hesperotestudo   anatomy that determined whether they could burrow or not.  If they couldn’t dig their own burrows, they must have been dependent upon ground sloth and pampathere burrows.) These burrow systems provided refuge, not only for ground sloths and pampatheres (a kind of giant armadillo) but many other species as well.  They served as shelter for hundreds of species of small vertebrates and invertebrates, much like the tunnels of prairie dogs and gopher tortoises do today.  I hypothesize ground sloths were immune to snake bite venom because their burrows likely served as winter dens for rattlensakes.  Large predators, bears, and peccaries probably used abandoned ground sloth burrows for shelter.  Ground sloths excavated large quantities of subsoil too and when mixed with topsoil these mounds supported unique plant communities.  It seems likely the plants that grew around ground sloth burrows were edible for ground sloths and many other herbivores.  I recently watched an episode of Expeditions with Patrick McMillan that showed a prairie dog town surrounded by mallow flowers.  Fossil coprolites indicate globe mallow was a favorite food of 1 species of ground sloth.

I doubt ground sloths lived in dense colonies like prairie dogs.  I guess there was normally 1 active ground sloth burrow every 3-5 square miles.  Intraspecific competition, if it existed in ground sloths, may have limited population density.  The burrows helped ground sloths survive climatic extremes, and the large powerful animals were able to hold their own against predators, but they were defenseless against men with projectile weapons.  They were the easiest of all the megafauna for men to kill–the most meat from the least effort–and therefore were the first to be hunted into extinction.  The increased frequency of fires set by humans may have also contributed to their extinction.  Instinct told them to take refuge in their burrows during lightning storms when the flashes of electricity ignited natural fires, but fires set by humans could overcome them at any time of year during sunny conditions.  Ground sloths could not outrun fires.  All the animals and plants that benefitted or completely depended upon ground sloths, pampatheres, and giant tortoises had to re-adapt to their absence.

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Photo of a prairie dog colony.  Though giant ground sloths and giant tortoises probably didn’t live in dense colonies, they also dug burrows throughout their range and were important keystone species that played as an important role in ecosystems as prairie dogs do today.  They were likely the first organisms to be wiped out by humans in North America.

The largest most dangerous predators were the next group of animals to be eliminated from the landscape.  Giant short-faced bears, giant lions, and fanged cats had no fear of people, yet they were no match for groups of men with projectile weapons.  Many of these animals were killed while contesting carcasses with people.  The decline of large carnivores likely occurred simultaneously with the extermination of mammoths and mastodons.  During the Boling/Alerod interstadial mastodon populations should have been increasing because this semi-aquatic species benefitted from the expansion of wetlands.  But humans drove mammoths and mastodons away from their favorite foraging grounds and watering holes, and they disrupted their migration routes.  The reproductive rates were too slow to keep up with human hunting pressure.

African elephants influence their environment today.  In Kruger National Park elephants uproot 1500 mature trees annually.  They convert forest into open savannah.  Mammoths and mastodons likely kept environments in southeastern North America in a constant state of flux.  The environment was patchy with various stages of forest succession located adjacent to other stages–meadow next to shrubby thickets alongside 2nd growth and mature woodland.  There were groves of large seeded fruits such as Osage orange, pawpaw, honey locust, and persimmon that had been planted in the excrement of the proboscideans.  After mammoths  and mastodons were eliminated the patchy woodland and grassland transformed into a monolithic mature forest that supported few large mammals.  The loss of patchy habitat hurt populations of llama, peccary, and tapir.  Even some small animals disappeared from the region, as their favored micro-environment converted to deep forest.

Next came the slaughter of horses and bison.  With mammoths and mastodons gone, the final populations of horses in southeastern North America were hemmed into smaller grasslands because forests expanded now that trees weren’t being uprooted with the same frequency.  This made them more vulnerable to human hunters.  Bison benefitted from their co-existence with horses.  Bison feed on the nutritious new growth spurred by horses grazing tall grass.  But the elimination of horses also meant bison, those that avoided human hunters, had a hard time surviving in the region.

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Pleistocene horses may have improved the quality of grazing for bison.

The loss of megafauna spelled the end of the line for a long list of commensal species including condors, and extinct species of vultures, eagles,  storks, and cowbirds.  There wasn’t enough prey for dire wolves and even extinct subspecies of jaguars and cougars.  Genetic evidence suggests all North American cougars descend from a population originating in South America 10,000 years ago.  Eventually, cougars recolonized the region, probably from a population that evolved a tendency to avoid man and prey on small game as well as deer.  And after European diseases decimated Indian populations, bison, and horses introduced by the Spanish recolonized the region as well.

References:

Malhi, Y. et. al.

“Megafauna and Ecosystem Function from the Pleistocene to the Anthropocene”

PNAS 113 (4) 2015

Smith, F.A. et. al.

“Unraveling the Consequences of the Terminal Pleistocene Megafauna Extinction on Mammal Community Assembly”

Ecography 39 2015

100 Species of Reptiles and Amphibians along the Altamaha River, Georgia

July 17, 2017

The corridor along the Altamaha River drainage is the best remaining wilderness in Georgia.  The land here is protected by 11 state wildlife management areas and 2 private landowners.  The Nature Conservancy owns Moody Forest, and the Orianne Indigo Snake Society owns land that hosts the greatest variety of reptiles and amphibians in the state.  Scientists have recently begun studying this largely undeveloped corridor.  From 2008-2016 scientists conducted the first comprehensive survey of reptiles and amphibians along this river system.  They used intensive group searches, turtle traps, and drift fences to find species; and they listened for frog calls.  Drift fences are barriers interspersed with pitfall traps.  Smaller reptiles and amphibians attempt to go around the barriers and fall into the traps.  Surveyors collected an astonishing 100 species, indicating the region has the richest diversity of reptile and amphibian species in the state.  Fort Stewart army base ranks 2nd with 97 species, and the Okefenokee Swamp hosts 88 species.

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Map of the Altamaha River Drainage.  The Altamaha is fed by 3 major tributaries–the Oconee, Ocmulgee, and Ohoopee.

Scientists catalogued 59 species of reptiles and 41 species of amphibians along the Altamaha River.  This number includes 17 species that are considered endangered by the federal and/or state governments, including indigo snake, diamondback rattlesnake, southern hog-nosed snake, rainbow snake, harlequin coral snake, pine snake, pine woods litter snake, slender glass lizard, mole skink, gopher tortoise, spotted turtle, southern dusky salamander, and gopher frog.

Surprisingly, cottonmouth water moccasins were found at less than half the sites surveyed, and they were absent from the main branch of the river.  The authors of this study suggest regular flooding “scours” riverside vegetation, eliminating the cover favored by the venomous snakes.  On the other hand river cooters (Pseudemys concinna) were found to be abundant in the river, though according to the preceding scientific literature they were not known to be present here.

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River cooters are common in the main branch of the Altamaha River.  Before the below referenced survey was conducted, reptiles and amphibians along this river were so little studied, this species was unrecorded in the scientific literature as living in the river.

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Red salamanders (Pseudotriton ruber) reach the southeasternmost limit of their range at the Altamaha River.  This waterway is a geographical barrier for 14 species of reptiles and amphibians.

species photo

The pine woods litter snake (Rhadinia flavilata) reaches the northern limit of its range at the Altamaha River.  This species grows to about 1 foot in length and mostly lives underground.  They are venomous but have rear fangs that are probably unable to break human skin.  They feed on small reptiles and amphibians and are no danger to people.

The reason such a high diversity of species occurs along the Altamaha River is the great variety of habitats.  The corridor hosts open water, bottomland hardwoods, cypress/tupelo swamps, longleaf pine savannahs, sandhills, Carolina Bays, and muddy seepage areas at the bottom of north-facing slopes.  However, the river itself serves as a barrier blocking movement of some species’ populations.  The Altamaha River is the southeasternmost range limit for 13 species, and the northernmost range limit for 1 species.

The high number of reptile and amphibian species is evidence the region of the Altamaha River has been climatically stable for millions of years.  The vicissitudes of Pleistocene climate fluctuations were muted here.  During cold arid stadials swampy wetlands shrunk in size but persisted as relics, while savannahs and scrubby sandhill habitat expanded.  Currently, wetland habitat has expanded but before European settlement grassland and scrub habitat were still extensive.  Western Georgia and Alabama have also experience long term climatic stability.  (See:

https://markgelbart.wordpress.com/2015/04/28/the-pleistocene-ridge-and-valley-reptile-corridor/

https://markgelbart.wordpress.com/2015/08/21/extralimital-species-of-pleistocene-aged-turtle-remains-found-in-the-upper-coastal-plain-of-alabama/

)  Like the black prairie region of Alabama, the Altamaha river also undoubtedly served as a refuge for species of reptiles whose current range was obliterated by an ice sheet during Ice Ages.  Blanding’s and wood turtles may have extended their range this far south then.  Extinct giant tortoises (Hesperotestudo crassicutata and H. incisa) likely lived alongside their smaller cousin, the gopher tortoise.  But otherwise the modern species list of reptiles and amphibians in the region is mostly unchanged from the Pleistocene.

Reference:

Stevenson, Dirk, and Houston Chandler

“The Herpetofauna of Conservation Lands along the Altamaha River, Georgia”

Southeastern Naturalist 16 (2) 2017