Journey of the Pawpaw Seeds

Dinosaurs probably ate pawpaws.  The large size of the fruit likely evolved to attract hungry dinosaurs that then deposited the still viable seeds in piles of dung. Scientists identified fossil pawpaw leaves from both late Cretaceous and Eocene age strata.  Though many  Cretaceous plant genera didn’t survive the K-T impact that rubbed out the dinosaurs, pawpaws along with fig, sycamore, and laurel did.  Pawpaws profusely produce sucker roots, and this habit likely allowed them to regrow after the cometary impact incinerated above-ground vegetation.  The species of pawpaw that grew during the Eocene was Asimina eocenica.  Fossil leaves, or rather impressions, of this species have been found in Texas, Colorado, and Wyoming.  Pawpaws no longer range into the latter 2 states, but, of course, climate was much warmer during the Eocene.

There are 7 species of pawpaws.  The most common is the eastern pawpaw (A. triloba) which ranges throughout most of Eastern and Midwestern North America and is found in 26 states.  All other species of pawpaws occur either in south Georgia, Alabama, and Florida or are found exclusively in Florida.  The list of other pawpaw species includes slimleaf pawpaw (A. longifolia), big flower pawpaw (A. obovata), small flower pawpaw (A. parviflora), dwarf pawpaw (A. pygmea), netted pawpaw (A. reticulata), and 4 petal pawpaw (A. tetramera).  The great number of species found in Florida might suggest this may have been a center of evolutionary origin, but pawpaws first evolved before Florida even existed. Instead, pawpaws likely speciated in this region when high interglacial sea levels isolated various populations.  Pawpaws are the only genera within the Annonacea family that can survive in temperate climates.  All other species within this family such as custard apple, cherimoya, and sweetsop are restricted to tropical regions.  The larva of the zebra swallowtail butterfly (Protographium marcellus) feeds exclusively on pawpaw leaves, and it also is a rare temperate member of a mostly tropical subfamily.  There are 150 species of Graphinii butterlies, and the zebra swallowtail is 1 of only 2 species that occur in temperate climates.  There were probably more species in the Annonacea family and Graphinni subfamily that occurred in North America during the Miocene when climate was more tropical to subtroptical, but pawpaw and zebra swallowtails were the only ones that evolved the ability to survive frosts.

Scientists believe the present day patchy distribution of pawpaws indicates it depended upon now extinct megafauna for dispersal.  Beasts such as mastodons and ground sloths ate the large fruit and deposited the seeds throughout the environment.  Today, pawpaws mostly grow as an understory tree in shady bottomland forests, but they produce more fruit in sunny locations.  It seems probable that in the past mastodons would carry the fruit away from the shade in their alimentary tracts and defecate the seeds in a sunnier spot.  In a recent experiment horses and Asian elephants refused to eat pawpaws.  However, mastodons were not the same species as the Asian elephant, and they co-existed with pawpaws (an exceptionally nutritious food source) for millions of years.  Despite the results of this experiment, I believe mastodons ate pawpaws.  Genetic studies suggest pawpaws still have high genetic diversity because not enough time has passed since the extinction of their megafaunal dispersers.  Native Americans cultivated orchards of pawpaws, and  Iroquois Indians may have spread the fruit to its northernmost range limits.

Pawpaw fruit.  I grew saplings from these seeds.  The fruit is very sweet, has the texture of a cooked sweet potato, and exudes a tropical aroma.

Pawpaws are not well known today because they are difficult to market and cultivate.  The fruit has a shelf life of 2 weeks, so it can’t be warehoused, though it can be frozen.  Experimental breeding may eventually prolong the shelf life, however.  Wild strawberries have a shelf life of 1 day, but cultivated strawberries have been bred to last at least a week.  Pawpaws grow slowly and have low pollination rates and thus low fruit production.  Bees don’t pollinate pawpaw flowers.  Instead, the red flesh color of the fruit attracts scavenging beetles, fruit flies, and blow flies.  Flies and beetles are less efficient pollinators than bees.  The center of modern day pawpaw cultivation is in Kentucky.  Many new varieties are being developed and perhaps soon, they will be found in grocery stores or farmer’s markets.  All but 2 of the 60 varieties grown during the early 19th century have been completely lost as the fruit became forgotten by urban and suburban spawn of the rural folks who grew them.

A nice lady from Indiana sent me some pawpaw fruit almost 6 years ago.  I was able to germinate 5 saplings from 30 seeds.  The saplings are growing slowly and the top trunk of 2 of them broke off last fall.  I’m not sure why this happened. I don’t see zebra swallowtails in my neighborhood, but some insect, perhaps another species of swallowtail larva, has been eating the leaves.  I doubt I’ll ever get fruit from these trees.

The best of my 5 year old pawpaw trees.  I’m not going to transplant it.  Thick roots are already growing through holes in the bottom of the pot.

Compare the above 5 year old pawpaw sapling with this 4 year old peach tree that I also planted from seed in my yard.  The peach tree is 12 feet tall and loaded with fruit.  Click to enlarge.

References:

Berrry, Ed

“The Lower Eocene Floras of Southeastern North America”

U.S. Geological Professional Paper 91 1916

Lu, Li; J. Lowe, and S. Crabtree

“Genetic Variation in Pawpaw Cultivation Using Marosatellite Analysis”

Journal of the American Society of Horticulture 2011

Homaza, Jose

“The Pawpaw, a Forgotten North American Fruit Tree

http://www.arboretum.harvard.edu

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A Pleistocene Cloud Forest

Cloud forests are lush environments unique to high elevations located within tropical latitudes.  Vines cover evergreen trees and ferns carpet the ground.  Cloud forests occur along the Andes Mountains from Central America to Argentina at elevations between 3600-10,800 feet, and most are frost free due to the tropical latitude, though they are cooler than lowland forests.  The low seasonality of cloud forests allows for a diverse assemblage of flora and fauna.  Some common plant species found growing in South American cloud forests are elephant ear, strangler fig, and walking palm.  Over 400 species of birds reside in cloud forests including an astonishing 30 species of hummingbirds.  Mammals such as tapir, peccary, brocket deer, jaguar, cougar, ocelot, and spectacled bear roam cloud forests.  Even more species of reptiles and amphibians abound in the thick vegetation of the understory.  Huge beetles and a butterfly with see-through wings are just some of the countless insects that thrive in cloud forests.

Location of cloud forests around the world.

A cloud forest in Ecuador.

Walking palm trees.

Invisible wings make this butterfly hard for predatory birds to see.

A site with evidence of a Pleistocene-aged cloud forest was unearthed during the construction of an highway in Ecuador.  Scientists examined pollen, geochemistry, and charcoal excavated from strata here dated to between 45,000 years BP-42,000 years BP. During those 3000 years the site went through 3 successional stages.  Pollen evidence suggests during the initial stage that it was a valley floor swamp dominated by grass, aster flowers, and plants in the nightshade family.  This environment was replaced by a forest of holly and plants in the Melstomataceeae and Weinmannia families.  Melastomataceae is a family of tropical flowering plants, and the Weinmannia family includes 65 tropical plants.  This stage succeeded to an environment dominated by alder, myrtle, and plants in the hedyosum genus which includes 65 tropical species.  The latter 2 stages consisted of plant compositions that don’t occur in present day cloud forests.

The authors of this study also measured the amount of sporormiella in the sediment.  Sporormiella is a dung fungus and is used as a proxy for megafauna abundance when fossil evidence is not available.  The amount of sporormiella suggests megafauna were present but not abundant.  Ground sloths, giant armadillos, and gompotheres (a type of mastodon) compose part of the regional fossil record here.  These species were likely the source of the sporormiella in the 42,000 year old sediment.

Fire is rare in montane cloud forests, but there are plenty of other agents of change that cause the environment to go through successional stages.  Landslides on steep slopes after heavy rains can demolish a forest, opening an opportunity for pioneer plants.  Wind throws and forest dieback from old age, disease, or insect infestation also opens up space for pioneer species.  Megafauna probably had just a minor impact on Pleistocene cloud forests because they were not abundant here and plant growth is rapid.  The authors of this study did find volcanic ash in the sediment.  Volcanic-sparked fires do burn some cloud forests, forcing the environment to regenerate through several successive stages.

Reference:

Loughline, N.; et. al.

“Landscape Scale Drivers of Ecosystem Change in the Montane Forest of the Eastern Andean Flank, Ecuador”

Paleogeography, Paleoclimatology, and Paleoecology 2017

Speculative Distributions of Megafauna in Georgia 36,000 years BP

A recent statistical study estimated the abundance and natural ranges of megafauna species (mammals over 40 pounds), if man didn’t exist today.  They analyzed 5,742 megafauna species that have existed over the past 130,000 years, a time span including a full glacial/interglacial cycle.  Not surprisingly, they concluded the natural ranges and abundance of megafauna would be much greater today, if not for man.

Maps showing natural ranges and abundance of megafauna.  The top shows today’s abundance.  The bottom shows abundance today, if man didn’t exist.  Map is from the below reference.

This study inspired me to draw speculative range maps for selected megafauna species that lived in Georgia 36,000 years ago–long before people ruined the wilderness.  I chose this time period because it was an interstadial, a warmer wetter climate phase within the last Ice Age, and I think wildlife populations were higher then than during the Full Glacial Maximum when at least some of Georgia consisted of desert-like habitat.  My maps are educated guesses because the Pleistocene fossil record of Georgia is extremely incomplete.  Megafauna populations were not evenly distributed throughout the state.  I assumed the northern part of the state held more forest and woodland, while the southern half hosted more grassland.  But both environments existed in most of the state, often side-by-side.  Therefore, forest and forest edge species such as tapirs and long-nosed peccaries were more abundant in the northern part of the state.  Bison and horse were more numerous on the coastal plain.  Some animals migrated in and out of the state.  Isotopic evidence suggest mastodons moved back and forth between Florida and Georgia.  Like leaders of today’s elephant herds, experienced matriarchs knew where rich sources of food and mineral licks were located.  Some herds of mammoths probably moved great distances as well.  Flat-headed peccaries likely favored the sand hill scrub habitat along the fall line.

Evidence of caribou in north Georgia dates to the Last Glacial Maximum, but I believe they were so abundant even during interstadials that some herds wandered as far south as Georgia.  There is no fossil evidence of helmeted musk-ox, stag-moose, giant lion, or saber-tooth in Georgia.  I’m certain giant lion and saber-tooth did range into Georgia, and it seems probable helmeted musk-ox and stag-moose did as well.  Fossil evidence of giant lions has been found in Florida and Mississippi.  Saber-tooth bones have been recovered from all the states surrounding Georgia.  Fossil remains of stag-moose and helmeted musk-ox have been excavated from sites on the same latitude as Georgia.

The dots on my maps don’t represent any specific numerical value, but the bigger ones indicate larger populations. The maps include the 10,000 square miles of continental shelf that was above sea level between ~83,000 years BP-~7800 years BP.

Range maps of selected megafauna species in Georgia 36,000 years ago.  Click to enlarge.  I know the labels on the maps are hard to see so from left to right on the top row they are mastodon, mammoth, Jefferson’s ground sloth, stag-moose, stout-legged llama, large-headed llama.  Middle row from left to right: long-horned bison, horse, long-nosed peccary, helmeted musk-ox, giant beaver, saber-tooth.  Bottom row from left to right: tapir, caribou, flat-headed peccary, giant lion, jaguar, dire wolf.

Reference:

Faurby, S; and J.C. Svenning

“Historic and Pre-Historic Human-Driven Extinctions have Reshaped Global Mammal Diversity Patterns”

Diversity and Distribution 21 (10) Augusts 2015

The Tumbling Waters Trail in the Coosawattee Wildlife Management Area

I spent part of spring break at a Bird’s Eye View Cabin in Ellijay, Georgia.  The cabin is on an overbuilt ridge overlooking a valley.  All the species of animals I observed were the same species that are commonly found near my house in Augusta, Georgia.  I saw a turkey vulture eating a road-killed opossum, a raccoon, gray squirrels, bluebirds, an house finch, a robin, a tufted titmouse, and I heard rufous-sided towhees, cardinals, mourning doves, pileated woodpeckers, chickadees, and an hawk.

View of the valley from the Bird’s Eye View Cabin.

We went on an excursion to the Tumbling Waters Trail next to Carter’s Lake, named after that anti-Semite, Jimmy Carter.  I didn’t see any wildlife here, aside from a few dusky wing and tiger swallowtail butterflies.  The trail goes through a forest of oak and hemlock with an undergrowth of rhododendron and ferns, but most of the hemlock trees are dead.  Ice Age forests in north Georgia were dominated by spruce with some oak.  When climate shifted to warmer stages spruce trees started dying, creating more space for oaks, and the environment may have been somewhat similar in appearance, though with older trees. This time of the year about the only greenery in this region are the food plots planted to maximize populations of deer and turkey.  The Coosawattee Wildlife Management Area is 9 square miles of high ridges alternating with narrow stream valleys.  I found oak, hickory, beech, white pine, and Virginia pine.

The trail is between a steep hill and Carter’s Lake.

Carter’s Lake.

Dead hemlock tree in the center of the photo and fallen dead hemlocks in the background.

This is a wildlife management food plot.  It consisted of wheat and peas, I think.

 

 

 

 

 

 

 

 

 

 

 

 

 

I didn’t have time to finish the trail, so I ripped off a photo of Tumbling Waters from the internet.  This is where the Coosawattee River empties into Carter’s Lake.  The reservoir probably inundated many beautiful shoals like this.

Sadistic American Safari Hunters are Contributing to the Extinction of Africa’s Megafauna

Until well into the 20th century tropical diseases and tribal warfare left large areas of Africa uninhabited, and megafauna flourished.  An estimated 10 million elephants lived on the continent in 1900 and populations of rhinos, giraffes, zebras, lions, and other species were much higher than they are today.  Now, there are just 430,000 elephants living in Africa, and all of Africa’s megafauna are in danger of extinction.  The biggest threats are from overpopulation of people and loss of habitat.  Farmers convert wild lands into agricultural plots, and pastoralists with their increasing herds of cattle will not tolerate ungulates competing for grazing range or predator attacks on their livestock.  Illegal poaching is another major threat.  Trophy hunters from America claim they are helping to protect the last remaining populations of megafauna by supporting local groups that protect hunting preserves from poachers.  Instead, these sadistic safari hunters are contributing to the ongoing extinction of Africa’s most iconic animals.

For a price hunters can still go on a safari and kill rare mammals.  Here are some of the prices on the internet I found for guided safari hunts: elephant ($38,000), endangered white rhino ($66,790), lion-leopard-buffalo ($32,500 for a 26 day safari), zebra ($3500), baboon or jackal ($300).  Giraffes are pretty cheap too–$3450.  Incidentally, giraffe populations are in severe decline.  1 hunter paid $350,000 to kill an extremely rare black rhino.  By contrast a 4 day photographic safari costs just $2500. I am not against sustainable hunting for food, but the idea that rich people would spend this much money to slaughter rare animals in poor countries disgusts me.  This is what they do with their recreational budget?  Travel across the world to wipe out the last remaining populations of iconic animals with high powered rifles? These people are sick.  They make me think of the Nazis who killed my relatives during the Holocaust.

Here is an example of a Richie Rich douchebag on a safari hunt.  This is 1 of Donald Trump’s sons. He paid a fortune to murder a leopard.  He and his brother went on a safari and killed a leopard, civet cat, antelope, and buffalo. Why the hell would anyone kill a civet cat? He bragged about giving the antelope meat to the locals…the people who can’t afford to hunt these animals themselves.  What a jerk.  Trump’s entire family are a bunch of crooks who are using the White House to personally enrich themselves.  The U.S. is a disgrace for electing such a racist sexist pig to be president.

The claim that these safari hunts help conservation efforts is dubious at best and downright false in most cases.  First of all, there is a moral disconnect between letting rich American hunters slaughter wildlife for trophies,while local poor people are forbidden from hunting for bush meat to help feed their families.  This system stokes the kind of anti-colonial resentment that would foster sympathy for the poachers.  Then, there is the corruption.  Most of these African countries are so corrupt that money spent on safari hunts is pocketed by a few local gangster autocrats, and it does not go toward conserving the wildlife.  For example the $350,000 the hunter spent on killing that black rhino that I mentioned above went to an organization that doesn’t even help conserve black rhinos.  The money is supposed to go to guards that protect the big game animals, but instead it invariably ends up in the hands of some corrupt local politician who doesn’t give a shit about wildlife.  The safari hunters themselves are frequently corrupt.  They often bribe guides to let them get extra trophies above their limit.  Safari hunters claim they only shoot animals past their breeding age.  This demonstrates ignorance about basic biology, and it a ridiculous lie anyway.  None of the big game species they hunt ever live long enough to become infertile with age.  Moreover, they purposefully shoot the best looking trophies–the individuals with the largest horns and the lions with the most luxurious manes–and these animals are the strongest most fertile specimens within the population.  A noted wildlife photographer saw entire lion prides in Botswana wiped out by trophy hunters.  The safari hunters killed all the adult males, so the only male lions left in the area were the cubs that grew up and mated with their mothers, causing inbreeding that led to local extirpation of the pride.  A recent scientific study determined that trophy hunting so weakens the gene pool that it could eventually lead to the extinction of African megafauna.

I think African countries should promote photographic safaris instead of hunting safaris.  Money brought in by safari hunting amounts to less than 1% of tourism dollars brought into Africa by foreigners.  An increase in photographic safaris could easily replace this revenue.  Nevertheless, African megafauna is in big trouble.  As long as a certain percentage of the billion Chinese who live on earth are dumb enough to believe rhino horn is an aphrodisiac, I just don’t see how poaching can be stopped in corrupt African countries.  “Conservation” by safari hunters is a colossal lie that is only contributing to the extinction of these magnificent mammals.

Reference:

Knell, R.; and Carlos Marinez-Ruiz

“Selective Harvest Focused on Sexual Signal Traits can lead to Extinction Under Directional Environmental Change”

Proceedings of the Royal Society of Biological Science November 2017