Archive for the ‘invertebrates’ Category

Disjunct Populations of Western Insects Occur on Black Belt Prairies of Southeastern North America

September 4, 2017

The Black Belt Prairie region extends through Alabama and Mississippi with additional isolated patches in Georgia and Tennessee.  There is a different Black Prairie region in east Texas.  The chalky soils of Black Prairies favor grass over trees, and in the southeast they produce a mosaic of forest and prairie.  Western species of plants such as little bluestem grass grow on Black Prairie landscapes, and they attract species of insects not normally found in southeastern North America.  At least 15 species of insects that occur on western grasslands exist as disjunct populations on the Black Prairies located in southeastern North America.  This includes the white bee (Tetralonella albata)–a pollinator of prairie clover–as well as 4 species of long-horned beetles and 10 species of moths.  The red-femured long-horned beetle (Tetraodes femorataand the Texas long-horned beetle (T. texanus) feed upon milkweed.  Most of the moths are hosts on flowers in the aster family.

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Map of Black Belt prairie region in southeastern North America.  (Shaded orange.)  Although the map doesn’t show it, some isolated pockets of Black prairie occur in Georgia as well.

Bee on Dalea - Tetraloniella albata

The white bee occurs in disjunct populations in Mississippi and Arkansas.  The main population occurs from Colorado and Illinois to California.

Milkweed Longhorn Beetle (Tetraopes sp.) - Tetraopes femoratus

The red-femured long-horned beetle ranges from the Great Basin to Mexico.  Disjunct populations occur in the Blackland Prairie Region.

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Epiblema iowana–another western species found in the Black Belt prairie region plus 1 site in Florida.

A grassland corridor formerly must have connected the Great Plains grasslands with the Black Belt prairies of the southeast.  Some scientists speculate that before the last Ice Age this corridor may have existed along the Grand Prairie of Arkansas or through the Arkansas River Valley.  The Mississippi River was lower then and interspersed with lightly vegetated sandbars that allowed for insect passage between the 2 regions.  After the last Ice Age glacial meltwater expanded the Mississippi River, blocking insect passage, but a grassland corridor between the Great Plains and the southern Black Belt Prairie may have existed through cedar glades in Tennessee to Kentucky to Illinois where the Mississippi River was more narrow. Currently, the Mississippi River and forested habitat separate the 2 grassy regions.

During Ice Ages the Black Belt prairies may have served as a refuge for many species of grassland insects found in the Great Plains today.  Forests of jack pine and spruce replaced Great Plains grasslands during glacial phases.  Summers were cooler and shorter.  Species of insects that preferred grassland communities and long warm summers retreated to the Black Belt prairies and Gulf Coast grasslands of southeastern North America.  Populations considered disjunct today may actually be seed populations that replenish Great Plains insect fauna following the end of Ice Ages.

Reference:

Peacock, Evan; and Timothy Schauwecker

“Blackland Prairies of the Gulf Coastal Plain”

University of Alabama Press 2003

 

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Pleistocene Oysters (Crassostrea virginica)

March 14, 2017

Before humans harvested them, oysters lived longer, grew larger, and produced denser quantities of offspring.  Scientists compared oyster shells from Pleistocene-age oyster reefs with those from Native-American archaeological sites and modern harvests.  Pre-human contact oysters lived as long as 30 years, while oysters since human colonization never live longer than 6 years.  Pleistocene oysters grew up to 10.2 inches, pre-historic oysters from Native-American middens grew to 7.4 inches, and modern oysters reach 6.1 inches.  Native-Americans harvested oysters in a sustainable way, but populations of oysters since European colonization have been reduced by over 99%, despite restoration efforts.  Pollution and overharvesting have destroyed oyster numbers.  This is unfortunate because oyster reefs are a productive natural community, providing habitat for at least 303 species that have co-evolved with oysters over the past 135 million years, ever since these bivalves first evolved. Scientists estimate the original oyster population of Chesapeake Bay was capable of filtering the entire contents of this estuary in just a few days, so they help clean the water as well.  Modern day estuaries are suffering without more abundant populations of oysters.

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Ancient oyster midden.

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Pelican in front of a Georgia oyster reef at low tide.

A representative of every species living in oyster reefs could fill a big city aquarium.  Barnacles, mussels, clams, and bryozoans attach themselves to the reefs and live out their lives filter feeding just like their hosts.  Mud crabs (Eurypanopeus depressus) graze on the algae and detritus that accumulates on the reefs and sometimes feed upon the smaller oysters.  Oyster pea crabs (Pinnotheres) depend upon reefs for their very survival. The seashore springtail (Anurida maratima), unusual salt water insects, prey on microorganisms living on the reefs.  Amphipods, worms (Polydora and Polychaetas), anemones, mites, and hydroids are commensal animals dependent upon the existence of oyster reefs.  Boring sponges (Cliona) and starfish directly prey on the oysters.

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The seashore springtail is a true insect that lives on oyster reefs.

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The depressed mud crab grazes on algae, detritus, and small oysters on oyster reefs.

Many small species of fish swim in and around oyster reefs during low tide because the structure affords protection from predators.  Species of fish commonly found in Georgia oyster reefs include in order of abundance naked goby (Gobiosoma bosci), feather blenny (Hypoblennius hentzi), skilletfish (Gobiosox strumosus), seaboard goby (Gobiosoma ginsbingi), striped blenny (Chasmodes bosguianus), oyster toad fish (Opsanus sp.), and the crested blenny (Hypleurochilus geminatus).  During high tide larger fish such as sheepshead, black drum, and croakers move in and feed upon the shellfish and smaller fish living on the reef.

Image of Gobiosoma bosc (Naked goby)

The naked goby is the most common fish living in Georgia oyster reefs.  They feed upon worms, crustaceans, and dead open oysters.

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The skillet fish clings to oysters with its sucking mouth.

Land vertebrates forage oyster reefs during low tide.  Raccoons and wading birds find many a meal on the reefs.  Oyster catchers (Haematopus palliatus) specialize on feeding upon the oysters and other bivalves growing here.  Even boat-tailed grackles exploit oyster reefs–they eat the amphipods and pea crabs crawling over the reef.

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The American oystercatcher thrives on oyster reefs.

Oysters have a complex life cycle.  They expel sperm and eggs into the ocean water, and when these sex cells meet by chance they form larva.  (Oysters change sexes, so that males become females and vice-versa.  Some individuals are hermaphroditic  and expel sperm and egg at the same time.)  The larva lives in the zooplankton until they develop a foot.  The oyster senses pheromones from other oysters on a reef and will attach its foot to the structure where it will remain for the rest of its life, filter feeding upon diatoms, dinoflagellates, inorganic particles, bacteria, and marsh plant detritus.

Oyster reefs also have life cycles.  When oysters begin colonizing an area it is known as the clustering phase.  Oysters attach to each other and on old dead oyster shells during the accretionary stage, building reefs.  Eventually, oysters reach a vertical limit and start building the reef horizontally during the senescent phase.  Large reefs block sediment and shell debris carried by tidal currents and this action can create islands.  Little Egg Island in the middle of the Altamaha River mouth is an example of an island created by an oyster reef.

References:

Bahr, Leonard, William Larsen

“The Ecology of Intertidal Oyster Reefs of the S. Atlantic Coast: A Community Profile”

U.S. Geological Survey 1981

Lockwood, R.; K. Kusperck, S. Bonanani, and Gratt, A.

“Reconstructing Population Demographics and Paleoenvironment of Pleistocene Oyster Assemblages: Establishing a Baseline for Chesapeake Bay Restoration”

North American Paleontological Convention 2014

Rick, Turbin; et. al.

“Millenial-scale Sustainablity of the Chesapeake Bay Native American Oyster Fishery”

PNAS 2016

Wharton, Charles

The Natural Environments of Georgia

Georgia Department of Natural Resources 1978

The Amazing Fishing Spiders (Dolomedes sp.) are Greater than Jesus

March 6, 2017

Fishing spiders are more amazing than the so-called “amazing” Spider-Man. Fishing spiders really exist and have persevered for millions of years, while Spider-Man is a fictional character created by Steve Ditko in 1962.  Fishing spiders are greater than Jesus Christ because there is proof they can walk on water whereas there is little evidence the semi-fictional legend even existed.  The story of Jesus walking on water was invented by the unknown author of Mark, the oldest New Testament gospel, and it was plagiarized by the unknown authors of Matthew and John.  Their stories were so ridiculous they were too ashamed to attach their real names to them. Instead, they forged other people’s names to their scrolls, hoping to avoid ridicule.  Jesus could not walk on water.  The laws of physics as we understand them in the present day demonstrate he would sink.  But fishing spiders use hairs on their legs to stride on the surface tension of water, a feat I’m sure Jesus could not actually accomplish in real life.

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The striped fishing spider (Dolomedes scriptus) is large, growing up to 3 inches long.

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Fishing spider with dinner.

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Fishing spiders walk on water…like Jesus Christ allegedly could do.

Fishing spiders mostly hunt aquatic insects on top of the water, but they can also dive underwater to seize minnows, tadpoles, frogs, and crayfish.  They carry an air bubble with them attached to the hairs on their body when they dive underwater.  Their venomous fangs quickly deliver a mortal bite to their prey and the buoyant air bubble carries them back to the surface.  Fishing spiders are able to sense their prey the same way web-spinning spiders do.  Spiders detect vibrations made by insects captured in their web; fishing spiders feel vibrations made by prey moving through water.  Fishing spiders don’t need webbing to sense prey because water serves as their web.

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An Okefenokee fishing spider (D. okeefenokensis) with a crayfish.  I wonder how they get past the claws. They also prey on small frogs.

There are 9 species of fishing spiders native to North America in the Dolomedes genus.  8 of them are aquatic–the lone exception lives in trees.  The Okefenokee fishing spider lives in south Georgia and Florida but there are several species that occur as far north as southern Canada.  Striped fishing spiders were able to expand their range north following the end of the last Ice Age.  It would be interesting to know how long it took for this dispersal to take place.  It would also be interesting to know the evolutionary relationship between the 9 species and other closely related spiders.  It’s likely they evolved from terrestrial ancestors.  Alas, as far as I can determine, scientists have not yet studied Dolomedes genetics.

 

The Continent Conquering Human Flea (Pulex irritans)

January 8, 2017

A flea can jump 160 times its own body length–the equivalent of a 6 foot tall human jumping the length of over 3 football fields.  Most of the known 2500 species of fleas are ectoparasites that use this phenomenal jumping ability to leap from the ground to an host or from one host to another.  Scientists believe the human flea was originally a parasite of wild cavies, species of rodents native to South America.  9,000 years ago, South American Indians began domesticating a species of cavy, either Cavia tschudii or C. aperearesulting in the well known household pet, the guinea pig ( C. porcellus ).  The domestication process may have been instigated by the cavies rather than humans.  Cavies likely were attracted to the shelter of human dwellings where they fed on vegetal kitchen scraps.

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The human flea expanded to many times its size. Their toes serve as a lever that helps them jump many times their body length.

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The guinea pig is thought to be the original host of the human flea.  Fur traders spread the flea from South America to North America and across the Bering Strait to Asia.

By 7,000 years ago, guinea pigs were commonly raised in many South American Indian households.  Maintaining a population of 20 individuals yielded about 12 pounds of meat per month, so they served as a valuable source of food, lessening the need to hunt wild animals.  Fleas from guinea pigs made the leap to man and from there they conquered 5 continents.  According to the lead author of the below referenced study, they advanced through a “step by step gift exchange of furs from South to North America and over the Bering Strait.”  Fur traders slept on their skins and left flea larva living in the detritus of flea feces, dried blood, and human skin flakes that accumulated on their unwashed beds.  After mature fleas feed on blood, they lay their eggs in this detritus.  Human fleas were carried along Asian trade routes and they conquered Egypt by 6000 BP.  The Roman armies carried fleas from Egypt to southern Europe, and the Vikings may have carried fleas from North America to northern Europe.

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Roman legions and Vikings carried fleas with them to Europe.  Bubonic plague carried by fleas from rats to humans and back depopulated Europe.  Fleas were responsible for far more deaths than Romans and Vikings.

Human fleas made a colossal impact on human history.  Fleas jumping back and forth between rats and humans spread bubonic plague, a disease that killed an estimated 30%-60% of the European population during the years 1347-1350.  Much of Europe reverted back to wilderness following this depopulation.  The Romans and the Vikings thought they had conquered the world, but they are long gone.  Human fleas are still here and can be found in just about every hotel, even in the finest, most expensive chains.

Reference:

Panagiotakopulo, Eva; and Paul Buckland

“A Thousand Bites–Insect Introductions and Late Holocene Environments”

Quaternary Science Reviews November 2016

Red Rain in India was Caused by a Microorganism from Europe, not Outer Space

May 4, 2016

The Color Out of Space: H.P. Lovecraft One of the first stories I’ve read from Lovecraft. It’s basically about this meteor that falls on some farm property, and everything slowly changes.  While you just chant the whole time “Leave! Move somewhere else!”, they can’t because something bigger is keeping them there. What I really love about Lovecraft is nothing is ever simple and there’s seldom a happy ending.

An unusual meteorological occurrence in India reminds me of my favorite H.P. Lovecraft story–“The Colour out of Space.”

H.P. Lovecraft published the classic science fiction/horror story, “The Colour Out Of Space,” in 1927.  The story is about a meteor that crashes in a farmer’s field and causes strange unnatural changes to all the plants, animals, and people living in the vicinity of the impact zone.   It’s remarkably prescient because the story precedes scientific knowledge of radiation poisoning, and the descriptions of the meteor’s effects bear a resemblance to nuclear fallout, though Lovecraft implies a supernatural explanation.  This work of literature directly influenced the movie, “Five Million Years to Earth,” still often aired on Turner Classic Movies, and Stephen King’s novel The Tommyknockers, his last book written while he was under the influence of cocaine and alcohol.  Some literary analysts make the claim the aliens taking over people’s minds in King’s novel is a metaphor for the drugs taking control of the author before he succumbed to treatment.  (I disagree with Stephen King when he later admitted he thinks this was a bad novel.  I rank it in the upper 25% of his creations.)  Lovecraft’s theme of an alien life form effecting life on earth permeates much of the science fiction/horror genre.  Yet, this idea is not solely confined to the realm of fiction.  Many scientists think life on earth originated in outer space, a concept known as Panspermia.  They believe non-photosynthetic microorganisms, living deep inside meteorites, crash landed on earth and later evolved into all the life forms now existing on the planet.  (The microorganisms would have to have been inside the meteorite because they couldn’t have lived on the surface in space nor could they have survived the friction heat generated by entering earth’s atmosphere.)  Proponents of Panspermia Theory thought they had strong supporting evidence when a strange red rain periodically fell in India for 2 months in 2001.  They examined the rain under a microscope and observed single-celled organisms that appeared to be multiplying but had no apparent DNA.  They assumed the organisms originated in a meteor that broke apart in the atmosphere, releasing the extra-terrestrial spawn.

There have been many incidents of red rain falling in India.  Some scientists proposed this as evidence of  Panspermia.

Genetic tests determined the rain got its color from a species of algae that originated in Austria.

However, a more detailed study of the organisms found in the red rain determined they were a species of algae that lives in symbiosis with a species of European lichen.  A DNA analysis identified the microorganisms as spores of Trentepohlian annulata.  Weather conditions sent airborne spores into clouds blown over the ocean, and they eventually fell as rain on India.  The algae recently colonized lichen growing on Indian rubber trees.  Though this study probably disappoints Panspermia proponents, it does illustrate an amazing case of an organism’s dispersal capability.  The same weather patterns periodically recur–red rain in India has been reported as recently as 2012 and as long ago as 1896.

There may be no hard evidence supporting the Theory of Panspermia, but there is a curious fact about microorganisms in space that lends support to the concept.  Astronauts often discover thick disgusting layers of biofilm growing inside space stations.  The microorganisms were introduced by accidental contamination.   A scientific study showed bacteria reproduce and grow more rapidly in zero gravity conditions, resulting in a greater biomass.  This is especially hazardous for astronauts because the human immune system completely shuts down in zero gravity.  Maybe it’s just a coincidence that simple one-celled organisms thrive in weightless conditions of outer space.  Or maybe they are so well adapted to zero gravity because it is the condition from which they originated.

References:

Bast, Felix; Jackson Adnankunju, and F. Stocker

“European Species of Subaerial Green Algae Trentepohlian annulata (Trentepohliales, Uluphyreae) Caused Blood Rain in Kerala, India”

Journal of Phylogen Evolution Biology Feb 2015

Wouseong, Kim; et. al.

“Spaceflight Promotes Biofilm Formation of Pseudonomous aeriginori

PLOS ONE 2013

Pleistocene Dung Beetles

March 31, 2016

An odd thought occurred to me the other day involving Hindu reincarnation myths and dung beetles.  I happened to jog past a female rainbow scarab beetle (Phanaeus vintex), rolling a dog turd on the asphalt-topped road.  (Female scarab beetles lack the male’s horn, making the sexes easy to distinguish.)  Scarab beetles bury feces and lay their eggs in it.  Both the adults and larva eat shit.  Apparently, this particular scarab beetle was looking for soft earth where it could bury its offspring’s food supply, but it couldn’t find the end of the hard road–it kept rolling the turd in circles.  I felt sorry for the creature because it would roll the turd within inches of the side of the road, almost to the dirt, then it would turn around and roll it toward the other side.  A car ran over the turd, busting it into 3 pieces.  Undeterred, the dung beetle picked the largest piece left and began rolling it in circles again, never quite reaching the dirt for as long as I observed it.  I’m not familiar with the Hindu religion, but I think they believe human spirits can be reincarnated as animals.  Suppose the Hindu Gods punished a human, whose sin during life was laziness, by reincarnating his soul as a dung beetle stuck rolling a heavy turd on a hard surface where it could never find a soft place to rest.  The soul could spend an eternity of hard labor to make up for his earthly slothfulness.  In reality a dung beetle never gets discouraged because insects are automatons with no emotions.  Before man built hard roads the only environment where dung beetles could become indefinitely trapped rolling turds were large granite outcroppings.  Dung beetles are yet another organism suffering a high death toll because of man’s extensive road network.

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I saw this female rainbow scarab beetle rolling a dog turd on the street in front of my house.  It was aimlessly rolling it around in circles.  It just missed getting run over by cars.  Click to enlarge.

There are 3 types of dung utilization behaviors among the many species of dung beetles.  Some take a piece of shit and roll it some distance away from the manure pile before digging a hole and depositing an egg in it.  These dung beetles are known as “rollers” and include members of the Phanaeus genus.  The “tunnelers,” including members of the Onthophagus genus, dig holes adjacent and under the dung pile where they deposit their eggs.  The “dwellers” live and lay their eggs inside the dung pile.  These include members of the Aphodius genus, and they release chemicals that keep the dung patty moist.

It is likely the widespread extinction of megafauna at the end of the Pleistocene caused a drastic reduction in the abundance and diversity of dung beetles.  One study found that the diversity and size of dung beetle species in Africa was higher in regions with abundant populations of megafauna.  Researchers counted 50 species of dung beetles in savannahs where elephants still occurred, 41 species where just cattle ranged, and 30 species in regions with no large mammals.  Dung beetles that switched to donkey shit in regions where elephants became extirpated were reduced in size.

Most species of extinct Pleistocene dung beetles will likely remain unknown to science because the odds of preservation for insects are even lower than those for large vertebrates.  However, 3 extinct species have been recovered from the La Brea Tar Pits in California–Onthophagus everestae, Copris pristinus, and an unnamed species in the Phanaeus genus.  (It’s possible some of these may be extant but undiscovered, but so far no entomologist has found a living specimen.)  The only species of dung beetle found in a preserved mammoth turd is the still extant Aphodius fossor, a large insect found in cow and horse pastures of Eurasia and North America.  Aphodius fossor probably followed herds of megafauna across the Bering land bridge almost 2 million years ago.  The specimen of mammoth dung containing the sub-fossil dung beetle was recovered from Bechan Cave, Utah.  An excavation at Snowmass, Colorado has yielded the remains of 9 species of dung beetles associated with the bones of megafauna dating to 120,000 years BP-77,000 years BP.  Scientists have identified 3 of the species, and they still occur in the region.  The remains of the other 6 species are too fragmentary to positively identify to the species level, but they may or may not represent extinct beetles.  Dung beetles have yet to be discovered from giant ground sloth dung, but fly larva from the Diptera genus, and a fly pupa from the Scairidae family have been found in sloth shit occasionally preserved in caves.  Flies compete with dung beetles.  Some species of dung beetles have evolved to prey on fly larva they capture inside feces.

Aphodius fossor - David Gould - The Spearwort Fields - 06 July 2014

Aphodius fossor, the only species of dung beetle ever found inside mammoth feces, though without a doubt many species were attracted to piles of megafauna shit during the Pleistocene.  The rarity of manure preservation in the fossil record explains the absence of evidence for other species.

Dung Beetle Life Cycle

Life cycle of a dung beetle roller.  Some other species tunnel into dung and lay their eggs inside the patty.

Dung beetles are beneficial organisms that expedite the recycling of nutrients.  The adults and larva also serve as food for birds and mammalian insectivores.  Birds, moles, shrews, skunks, possums, and armadillos apparently don’t mind the taste of the manure-flavored beetle grubs.

References:

Hanski, Ilkka; and Yues Cambefust

Dung Beetle Ecology

Princeton University Press 2014

Krell, Frank-Thorsten

“Pleistocene Dung Beetles from MIS 5 at Ziegler Reservoir, Snowmass Village, Colorado (Coleoptera: Scarabaedae: Aphodine)”

Denver Museum of Nature and Science Annals 2014

Pierce, W. D.

“Fossil Arthropods of California: Descriptions of Dung Beetles (Scarabidae of the Tar Pits”

Bulletin of Southern California Academy of Science 1946

 

Pleistocene Spiders

August 5, 2015

My fascination with the ecology of southeastern North America prior to man’s colonization of the region is frustrating.  Most of the data dating to this time period has been lost to the ravages of time.  I can make educated guesses about the appearance of pristine landscapes untrammeled by man, but this is little better than conjecture based on the pollen and fossil records from a handful of sites.  Many species of plants produce so little pollen they don’t even register in samples collected by palynologists.  And the pollen that is recovered usually can’t be identified below the genera level.  So we know that pine may have produced up to 50% of the pollen at 1 site during a certain time span, but we don’t know whether it was from jack pine, a cool climate species, or longleaf pine, a denizen of warm climates.  But at least we have some data about Pleistocene plant composition.  There are thousands of species of spiders living in the south today, yet I’m unaware of a single Pleistocene-aged site in southeastern North America where the remains of spiders have been recovered.  Spiders have been a vital part of land ecosystems ever since life crept out of the sea.  Nevertheless, there is no evidence of spider species composition dating to the Pleistocene.  Spiders are soft bodied creatures, and their remains get crushed into dust over time.  The remains of hard-shelled beetles, millipedes, and snails have been found in cave deposits located in the southern Appalachians because their hard exoskeletons can remain intact for millennia.  Spiders were also certainly abundant in caves during the Pleistocene, but evidence of their presence is gone.

It’s unfortunate that we know nothing about spider species composition and distribution in the south during the Pleistocene. Even modern spiders are poorly known. There are over 120,000 species of spiders in the world, but only a tiny fraction of these have been studied in detail.  The vast majority of spider species have yet to be described and named in the scientific literature.  Spiders vastly outnumber the scientists willing to study them. Spiders have high rates of reproduction, and therefore evolve rapidly, making them an ideal candidate for an evolutionary biologist to study.  During the Pleistocene many present day species already existed, but there may have been some now extinct species.  Some were evolutionary ancestors of present day species, while others may have left no descendants.  The abundance of certain species varies annually for unknown reasons, perhaps chance.  Below are some interesting species of spiders.

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Artist’s depiction of a trapdoor spider (Ummidia sp.).  I can usually find 1 of these when I dig in my garden.

Common garden spider aka black and yellow argiope (Argiope aurantia).  They build big beautiful webs capable of catching small birds and bats.  Some natives use orb-weaver webs as fishing nets.  Spider webbing is incredibly strong.

Green lynx spiders  (Peucetian viridans) are beneficial for gardeners.  This individual caught a moth.  The larva of some species of moth eat through garden vegetables.

Spined Micrathena, Micrathena gracilis

A spined micrathena (Micrathena gracilis).

Diet of elusive red widow spider revealed by MU biologist

The red widow spider (Latrodectus bishop) lives in the Florida sandhills and feeds upon beetles.

The red widow spider inhabits the pine sandhills of Florida which were islands surrounded by ocean during the marine highstands of Pliocene and Pleistocene warm climate phases.  They construct funnel webs in rolled up palmetto leaves.  This ancient species specializes in capturing flying scarab beetles. The beetles fly low to avoid bat and common nighthawk (Chordeiles minor) predation, but this strategy makes them more likely to fly into red widow spider webs.  Red widows are related to the more common black widow spiders.  They exist as a relic population today but were likely more common when sand scrub habitat prevailed in the south during the late Pliocene/early Pleistocene.

The ancestor of spiders was closely related to the horseshoe crab.  It colonized land about 400 million years ago.  Fossil remains of spiders and spider webs dating to the Cretaceous (~100 million years BP) have been found.  Some were preserved in amber, and others were fossilized in layers of ash that turned to rock.  Though the Cretaceous species are extinct, scientists classify them as belonging to extant genera.

Earth will undoubtedly host spiders long after Homo sapiens becomes extinct.  The drastic changes man has wrought to the environment have barely phased spiders.  Compared to the changes spiders have seen over the 400 million years of their existence, anthropogenic effects are but a minor blip.  Look around, there are spiders inside your house now.

Reference:

Carrell, James; and Mark Deyrup

“Red Widow Spiders (Araneae: Theridiidae) Prey Extensively on Scarab Beetles Endemic in Florida Scrub”

Florida Entomologist 97 (1) March 2014

Pleistocene Pollinators

June 12, 2015

The media sure likes to generate panic.  It must be good for ratings.  Recently, American media outlets offered wall-to-wall coverage of the Ebola virus, a danger that eventually killed 2 or 3 people in the United States from a population of over 300 million.  During slow news cycles the media seems to always find some obscure disease of the month to fill air time.  Another constant well of media anxiety is anthropogenic-influenced climate change, even though its worst effects won’t be felt in our lifetimes, and there’s nothing we can do about it, unless people are willing to give up affordable electricity and cars.  A few years ago, media pundits started peeing in their pants about colony collapse disorder.  Without honeybees (Apis mellifera) they claimed there would be no pollination of fruits, nuts, and vegetables.   The world would have no fresh produce, and we’d be stuck with a boring diet of wind-pollinated grains.  In some regions their fear has come true.  In upstate New York colony collapse disorder wiped out so many honeybees, bee keepers were unable to provide any hives to help pollinate some apple orchards.  There was no loss of production. Orchards produced just as many apples without honeybees as they did with them.  Orchardists realized they’d been duped for decades by bee keepers into thinking they couldn’t grow fruit without paying for the rental of bee hives.

There are 140 species of native leaf cutter bees, including the blue orchard bee (Osmia lignaria), a species that is considered a better pollinator than non-native honeybees.  Moreover, there are many species of native bumblebees, butterflies, and wasps that pollinate flowers.  Native bees are such effective pollinators that honeybees were not missed at all.  As long as some natural areas are left in the vicinity of gardens and orchards, there will always be enough native pollinating insects; and honeybees will be completely unnecessary.  No need to worry about colony collapse disorder–many species of native bees are solitary and don’t nest in colonies.

Osmia-lignaria----WEB

Blue orchard bees are more effective pollinators than honey bees.

Southeastern blueberry bees and bumble bees pollinate my blueberry bushes.

Bumble Bee Queen

Bumblebee (Bombus impatiens)

I marvel at the lack of critical thinking among reporters and media pundits who are so quick to form opinions without realizing how illogical their conclusions are.  Europeans brought honeybees to North America 400 years ago, but before then, Native Americans successfully grew fruits and vegetables dependent upon insect pollination.  They farmed squash, beans, tomatoes, peppers, and plums.  Honeybees are just 1 species out of thousands of insect pollinators in America, yet the media know-it-alls led people to believe a nightmare scenario of no fruits or vegetables.  Not a single pundit during the panic of colony collapse disorder even realized honeybees are a non-native invasive species.  Usually, invasive species are another topic of unnecessary panic frequently reported upon by the media.

Thousands of species of American plants have depended upon insect pollinators for millions of years–ever since the evolution of flowering plants. The fossil record of these insects is scant.  When rare circumstances do occur that preserve ancient insects, the remains are usually so fragmentary they can’t be identified at the species or genera level.  Some nests of a species of leafcutter bee (M. gentillis) were found in the La Brea tar pits, California.  The same species still lives in the region today.  Studies of Pleistocene insects determined individual species adjusted their range according to fluctuating climate cycles, but no known large scale extinctions occurred during this era. (See: https://markgelbart.wordpress.com/2012/07/18/using-fossil-beetle-assemblages-to-determine-temperature-ranges-during-the-late-Pleistocene/) The insect pollinators we find in our yards today are the same species that lived during the Pleistocene.

Reference:

Bjerga, Alan

“Betting on Nature to Solve the Bee Crisis”

Bloomberg Business Week May 18-24, 2015

Blue Crabs (Callinectes sapidus) in Freshwater Springs

April 14, 2015

Marjorie Rawlings owned an orange grove in north central Florida from 1928-1941.  She was not a native southerner but used inheritance money to purchase the property.  Many of the characters she created in her short stories and novels were based on the people she met while she lived here.  Her most famous work is The Yearling, a novel later adapted for the big screen.  I think her most interesting book is her memoir of the 13 years she lived in a farm house next to her orange grove.  The title of this memoir is Cross Creek.  The relationships she developed with the “colored help” and the white “crackers” are entertaining reading.  Though progressive for her time, she clearly viewed black people as 2nd class citizens.  On 1 occasion she spent a week long hunting trip with her visiting brother.  When she returned to the farm she was outraged to discover the live-in “colored” help had spent the week enjoying a drunken orgy (literally…2 men and 1 woman in the same bed) and not a single chore had been completed.  Her brother joined her in chasing the help off the property at the point of a shotgun.  In my opinion Rawlings was at fault for being out hunting instead of supervising.  Moreover, today, her actions would be considered an illegal eviction, and she and her brother could be jailed for making terroristic threats.  However, if I could journey to 1930s Florida in a time machine and suggest this, all the white people there would think I was out of my mind.  How times have changed.

Marjorie Kinnan Rawlings with her dog - Cross Creek, Florida

Marjorie Rawlings, author of the famous novel–The Yearling.  This dog was accidentally poisoned.  She accused her neighbor of deliberately poisoning her dog, a charge he vehemently denied.  They feuded for a year before reconciling.

My favorite chapter in Cross Creek chronicled the local cuisine.  Bread here meant cornbread, cornpone, hoecakes, hushpuppies, or biscuits.  Meat meant salt pork, known here as “white bacon.”  Pork in 1930s America was much fattier than modern day pork.  White bacon was soaked in water, floured and fried.  The grease rendered from frying the fatty pork was used to season biscuits, cornpone, sweet potatoes, black-eyed peas, green beans, and greens.  These were the staple dishes but hunting and fishing supplemented the local diet with many exotic sources of protein such as alligator, rattlesnake, turtles and their eggs, limpkin, blackbirds, bear, and squirrel.  Rawlings accompanied men who went crabbing at night.  They caught crabs from a freshwater spring that flowed into the St. John’s River.  The men stood on boats and located crabs by shining lights into the clear water.  They used 12 foot poles with iron jaws on the end to snatch the crabs.

Crab

Blue Crab in Crystal River Spring, Florida. It’s probably a male.  The females stay in brackish water and migrate to waters with high salinity to release their eggs.

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Blue crab life cycle.

I was surprised to learn that blue crabs inhabit freshwater.  Apparently, during spring male blue crabs migrate in enormous numbers to brackish and fresh water.  During mating season the 2 sexes meet in brackish water to mate, and the females carry their fertilized eggs back to the saltier depths.  The larval stage of the blue crab is known as a zoeal.  As the zoeal grows, they shed their shells 7 times in a process known as molting.  Their bodies absorb calcium from the sea water and swell, and this extra calcium forms a hard exoskeleton.  Blue crabs are called megalops during the next stage of their life when  they move into water with lower salinity where they eventually transform into adult crabs.

Blue crabs outcompete and drive away crayfish in the freshwater springs they inhabit.  Both species eat the same foods, scavenging and actively hunting plant and animal material.  Blue crab larva can’t survive in freshwater.  If this species ever evolved that ability, they would eventually colonize freshwater creeks and rivers, causing a decline in crayfish abundance and diversity.  Fossil remains of the Callinectes genus date to about 15 million years ago, and Pleistocene-aged blue crab shells have been found from Massachusetts to the Caribbean and Texas.  It is an incredibly successful species.

Giant Leopard Moths and Red Wasps are Invading my Property

August 19, 2014

In some ways insects are more adaptable than large mammals.  Insects are capable of evolving in response to environmental change much more rapidly than large mammals because several generations can reproduce within the timespan of just 1 growing season, while some large mammals take decades to produce a single generation.  The presence of humans has obliterated 70% of North America’s large mammal species, but it hasn’t put a dent in insect populations.  I will never see a mammoth or saber-tooth in my backyard.  However, thousands of interesting species of insects invade my property, and they are active almost year round, though the coldest days of winter relegate most of them to dormancy.  Most of the insects I find on my property are likely the same species that inhabited this space during the Pleistocene.  Insects suffered few known extinctions at the end of the Ice Age but instead experienced shifts in range distributions. (See: https://markgelbart.wordpress.com/2012/07/18/using-fossil-beetle-assemblages-to-determine-temperature-ranges-during-the-late-pleistocene/).  Climate in my neighborhood (Augusta, Georgia) remained relatively stable during this transition, and the change in insect species composition has probably been minimal since then. Recently, I’ve encountered 2 species of insects that have occupied my homestead space for hundreds of thousands of years.  Maybe, I should change the title of this essay, and call it “humans invading moth and wasp territory.”

Giant Leopard Moth, Ecpantheria scribonia

 

 

 

 

 

 

 

 

 

Giant Leopard Moth (Hypercompe scribonia)

This woolly bear caterpillar is the larval stage of the giant leopard moth.

The giant leopard moth (Hypercompe scribonia) is a large species with a wingspan of nearly 3 inches.  It has beautiful teardrop-shaped spots on its wings.  That is the description I googled to help me identify this species.  I found a dead specimen near my wildflower bed but didn’t take a photo. (I ripped off the above photos from google images.) It probably died after depositing fertilized eggs on 1 of the species of flowers growing in my garden.  Their larva are known as woolly bears (as are the larva of many other species of moths), and they feed on a wide variety of plants including but not restricted to violets, mustards, basil, trumpet vines, sunflowers, mulberry, magnolia, and locust.

 photo Daphnesdorm001_zps3665f00a.jpg

Red paper wasps (Polistes sp.) nesting between my screen door and side door.  It’s a door we never use, so I let them stay there.  Though manmade, it mimics a hollow tree stump or log in scarce supply in modern young forests.

A nest of red paper wasps (Polistes sp.) lives in the space between my side door and screened-in door.  There’s a hole in the screen, allowing access to this sheltered area.  Before humans built structures, paper wasps built their nests in hollow tree trunks, but there are few den trees in the young 2nd growth forests surrounding modern day suburbia.  I’m letting the wasps live in the doorway because: a) we never use the side door, b) they are not aggressive, unless defending their nest, and c) they are beneficial predators, destroying the kinds of caterpillars that like to eat their way through my garden.  Each cell of the wasp’s nest contains a wasp larva with a paralyzed caterpillar upon which it feeds.

There are 28 species of wasps in the Polistes genus that live in the southeast, and I’m not enough of an expert to identify the exact species to which my housemates belong.  I admire these little monsters–they invented paper millions of years before the 1st humans evolved.