Basal Angiosperms I

Angiosperms, the flowering plants, appeared in the fossil record during the age of dinosaurs.  Dinosaurs and flowering plants coevolved for tens of millions of years.  When the dinosaurs were wiped out (with the exception of birds) 66 million years ago, flowering plants survived. There are more than 300,000 described species of angiosperms and they have a dizzying array of sizes, forms, structures and reproductive systems. 

The standard story, taught for two centuries, is there are two kinds of angiosperms, monocots and dicots.  This story says monocots have flower parts in multiples of three, parallel veins in their leaves and one cotyledon (the mono cot), that stores and transports nutrients to the plant embryo. Their counterparts, the dicots, have flower parts in multiples of four or five, net veins in their leaves and two cotyledons.  There are numerous other differences between these groups but in the field these three characteristics can usually distinguish monocots from dicots. 

Leaves of pawpaw (Asimina triloba) a basal angiosperm

Botanists knew about some weird flowering plants that did not quite follow those simple rules but new evidence has forced a major change in the classification of angiosperms.  Monocots are still monocots but evolutionary plant biologists have blown up the dicots, largely based on DNA evidence.  This new classification still has standard dicots but they are now called eudicots, the true dicots.  Another group of flowering plants show characteristics of both monocots and eudicots and are classified as basal angiosperms.  Basal angiosperms do have many characteristics of eudicots like the above-mentioned two cotyledons and net veins, but many have flower parts in multiples of three and their pollen structure is more similar to that of monocots. 

Basal angiosperms branched off early from the main flowering plant evolutionary line.  These plants have characteristics in common with some of the first flowering plants.  I like to image herbivorous dinosaurs munching on basal angiosperms.  Here are some of the primitive attributes shown by the basal angiosperms; flowers often have parts in threes or multiples of threes (a monocot-like trait), flowers show little differentiation between petals and sepals, they make numerous pollen producing stamens and numerous egg bearing carpels.   

You might think these primitive flowering plants, these living fossils are rare, but they are not.  It is true they make up only about 3% of flowering plants.  It is also true that one order of basal angiosperms contains only one species and grows only on the Pacific island of New Caledonia. But other basal angiosperms are common, well known and produce striking flowers. 

Florida anise, Illicium floridanum, is a basal angiosperm found in westernmost Florida and adjacent areas of Alabama, Mississippi and Louisiana.  This small trees have bright green, lanceolate leaves.  When crushed, the leaves smell of licorice or according to one source, freshly caught fish.  In spring Florida anise bears striking maroon flowers.  The flowers typically have flower parts in multiples of threes with an unruly batch of petals, a dense ring of purple stamens and in the center another ring of carpels.  Florida anise like many deep purple flowers is fly pollinated. 

The purple flower of Florida anise ( Illicium floridanum)

Pawpaw (Asimina triloba) is a basal angiosperm found throughout eastern North America.  This small tree grows in the forest under-story, along watercourses and in North Carolina flowers in early spring.  The flower is purplish-brown with three sepals and six petals.  The flower produces a disagreeable odor that attracts carrion feeding insects like flies and beetles.  Pawpaw has another interesting insect interaction.  It serves as the host plant of the zebra swallowtail butterfly, Protographium marcellus.  Female zebra swallowtails lay their eggs on leaves or branches of pawpaw; the caterpillars eat the leaves and retain toxic plant compounds when they metamorphose into the butterfly stage.  This gives the butterfly some protection from predators. 

Early spring flower of pawpaw (Asimina triloba)

Pawpaw fruit in summer

Zebra swallowtail butterfly (Protographium marcellus) feeding on Lantana camara.
Pawpaw is the host plant for the larvae of this butterfly. 

I will follow up with more about the compelling basal angiosperms in another post.

A Tale of Two Turtles

Diane was driving and I was riding shotgun on the Blue Ridge Parkway recently.  This beautiful, mountainous, winding road offers unparalleled scenery, opportunities for botanizing and wildlife viewing.  As we crested a hill, we saw an eastern box turtle (Terrapene carolina carolina) crossing the road.  Diane swerved to miss the turtle and pulled over on the narrow shoulder.  I jumped out to try to help the turtle cross the road.  As I closed to within about 20 yards of the box turtle two cars topped the rise and were bearing down on the plodding reptile. 

Eastern Box Turtle (Terrapene carolina carolina) in North Carolina

Eastern box turtles range from the Great Lakes and New England south to Florida and from the eastern seaboard to the Mississippi River.  Several other sub-species of the box turtle can be found in Florida, the Gulf coast and west to the Great Plains.  Box turtles have a high domed carapace that is distinctly marked with bright yellow.  Box turtles are called box turtles because their lower shell, the plastron, has a hinged section they can close and withdraw their head and legs for protection, as if in a box.  Box turtles females have yellow eyes while the males have fierce orange eyes. With the exception of tortoises, box turtles are the most terrestrial of North American turtles spending most of their time walking rather than basking on logs in a pond.  Box turtles have a varied diet that includes fruits, small animals and even mushrooms that are poisonous to humans.  Box turtles are potentially long-lived.  Captive box turtles have lived in excess of 100 years but most animals in the wild do not reach such an advanced age.  One of their major causes of death is automobiles.  Eastern box turtle populations have declined and the species now listed by the International Union for the Conservation of Nature (IUCN) as Vulnerable, one step from endangered. 

Back to the Parkway.  Two cars came over the rise, the first one straddled the turtle but the second car hit the turtle directly with left front wheel.  The sound of the tire crushing the turtle was awful, like a ceramic bowl full of bread dough dropped on the floor.  As soon as it happened, I wheeled around.  I did not want to see the aftermath.  The driver of the second car slowed, rolled down the passenger-side window and asked, “Did I hit something?” I had a one-word answer.  “Turtle”. 

A Clemson University researcher placed rubber turtles on a busy road and found 7 drivers out of 267 deliberately hit the fake turtles in one hour.  I cannot say if the death of the box turtle on the Parkway was intentional but these results of the study are disturbing. 

A week later Diane and I were in Florida visiting Merritt Island.  The island is a complex of marshes, woodlands and beaches that are protected by a National Wildlife Refuge, a National Seashore and the Kennedy Space Center.  Merritt Island is one of the premier birding spots in Florida and we were seeking the Florida Scrub-Jay.  Once again, Diane was driving and I was in the passenger seat when we spotted another Florida native, a gopher tortoise.  Once again, a reptile was crossing a road.  Once again, Diane pulled over and I jumped out to try to get a cold-blooded creature across a road.  A pickup truck was coming.

Gopher tortoise (Gopherus polypemus) on Merritt Island, Florida

Gopher tortoises (Gopherus polyphemus) live on the Coastal Plain of the Southeast from South Carolina to Louisiana and down the Florida peninsula.  Like box turtles, the gopher tortoises have a high domed carapace but it is gray or dark brown in color.  Gopher tortoises eat plant material like saw palmetto berries, grass and even the pads of Opuntia cactus.  Their front legs are massive with impressive claws and with rear legs described as elephantine.  Those front legs allow these tortoises to dig burrows where they can escape the heat or shelter from cold.  Other animals use gopher tortoise burrows including eastern diamondback rattlesnakes, armadillos and Burrowing Owls.  Like box turtles, gopher tortoises are classified as Vulnerable by the IUCN. 

Fortunately for this tortoise, the driver of the pickup truck stopped.  I scooped up the gopher and moved it to the other side of the road.  The tortoise dodged that truck.

I cannot stop for every reptile crossing the road.  But, when it is moderately safe, I will try to help turtles across.  Sometimes it works. 

Alder Action

Male catkins of tag alder in late winter

Alders are shrubs or small trees and their distribution includes most of the northern hemisphere.  They are classified in the genus Alnus and are related to birches, hazels and hornbeams. In the southeastern United States, the most common alder is Alnus serrulata, the tag or hazel alder.  

The tag alders grow in swamps, along streams and the edges of lakes.  Tag alders begin to flower in late winter before any leaves open.  Alders have an interesting reproductive system.  They make different male and female flowers, thus they are monoecious with both sexes on the same plant. This is to distinguish them from dioecious plants like willows that have separate male and female plants.  Alnus serrulata produces male flowers in a hanging array called catkins.  Each catkin has dozens of small, yellowish-brown male flowers that have stamens that release pollen.  The flowers of the catkins are dull because alder is wind pollinated and do not have to attract pollinators like insects or birds.  The female flowers are also borne on catkins but these are reddish brown in color and resemble small cones.  The leaves of tag alder emerge in early April and are bright green with serrations along the margin.  Small, winged fruits develop in the female cones and fly through the air to establish new alders in late summer. 

Female catkins (cones) of tag alder in early spring

Female cones from the previous year

Tag alder leaves in early spring

Alders play a role in preventing erosion and stabilize stream banks.  They also have another ecological role in enriching the soil where they grow.  Alders have a symbiotic relationship with a nitrogen-fixing bacterium in the genus Frankia. Like the better-known symbiosis between legumes and their nitrogen-fixing bacteria, alders host colonies of their bacterium in root nodules.  The plant provides sugars and other organic molecules to the bacterium and the bacterium in turn converts nitrogen gas from the atmosphere into ammonia that is usable by the alder.

Look for alders as you walk along the edge of a pond or riverbank.  They have a lot going on.