Tropical Botany: Admiration and Awe

 

Epiphytic bromeliad (Guzmania sp.).
Savegre Valley, Costa Rica. 

Ecosystems are defined by their plant life. Deserts by their drought resistant plants like cacti, grasslands by, well, their grasses, temperate forests by their deciduous trees and tropical ecosystems by their sheer abundance of plant life.   Tropical forests occupy only 7% of the Earth’s surface but they host about half the world's plant species. 

I find botanizing in the tropics a daunting experience.  There are so many species, even whole families of plants I don’t know. This high diversity is typically coupled with low numbers of any one species, so on an hour’s hike you might see a particular plant only once.

On our recent trip to Costa Rica, led by Epic Nature Tours, we found an abundance of plants in rainforests, cloud forests and the highland scrub called paramo. 

Epiphytic bromeliads.
Savegre Valley, Costa Rica. 

Blushing Bromeliad (Neoregelia carolinae).
The cup of this plant is filled with water and flowers are emerging.
Cartago, Costa Rica. 

Buffy Tuftedcheek (Pseudocolaptes lawrencii)
feeding on a bromeliad.
Quetzal National Park, Costa Rica. 

Bromeliads are common epiphytes in the tropical forests of Central and South America.  The family Bromeliadaceae contains plants as different as Pineapples (Ananas comosus) and Spanish Moss (Tillandsia usneoides). Many of the Bromeliads we saw had a cup-shaped arrangement of leaves.  These cups fill with rainwater and provide homes and breeding sites for animals like frogs, salamanders and mosquitos.  An unusual bird specializes in feeding on bromeliads.  The Buffy Tuftedcheek (Pseudocolaptes lawrencii) is a brown bird with a buffy throat and cheeks.  It moves between bromeliads, probing for small animals that live within the plants.  

Dancing Lady Orchid (Oncidium nebulosum).
Tampanti National Park, Costa Rica. 

We also found epiphytic orchids in the rainforest.  Members of this large family can be found in every habitat except ice caps.  Their greatest diversity is in the tropics with Costa Rica boasting about 1400 species of orchids. 

Monstera tuberculata on the trunk of a tree.
Carara National Park,  Costa Rica. 

Still another epiphyte we encountered was Monstera tuberculata, a close relative of Philodendron.  Members of the genus Philodendron are natives of tropical America and are commonly grown as house plants.  The Monstera tuberculata we saw was a young plant with leaves tightly appressed to the trunk of a large rainforest tree. The plant grows up the trunk of the tree into the canopy, then switches to a hanging vine with large leaves. 

Heliconia bihai. Theses South American and
Caribbean plants grow well throughout the tropics.
Lankster Botanical Garden, Costa Rica. 

Leaf of Heliconia sp.
Carara National Park, Costa Rica.

Heliconias are common understory plants or small trees in the Neotropics.  They produce large, colorful flowers that are pollinated by hummingbirds.  Heliconias have large leaves much like their relatives the bananas (Musa sp.).  

 

Banana Passionflower (Passiflora tripartita).
Canon, Costa Rica. 

A rainforest vine hanging from the canopy caught our attention.  It was a Banana Passionflower (Passiflora tripatita) with bright pink flowers.  This species is native to the Andes of South America but has become established in many tropical and subtropical locations including the highlands of Costa Rica.

 

Blood of Christ (Columnea consanguinea).
Tapanti National  Park, Costa Rica. 
Photo by Diane Coggin.

Detail of Blood of Christ red leaf spots.
Tapanti National Park, Costa Rica.

Green-crowned Brilliant (Heliodoxa jacula)
a pollinator of the Blood of Christ plant. 
Fortuna, Costa Rica. 

Columnea consanguinea is another interesting rainforest plant.  It is a small shrub of the understory.  The leaves of the plant have translucent red spots that give it the common name, Blood of Christ.  Columnea consanguinea grows in the mountains of Central and South America and is pollinated primarily by the Green-crowned Brilliant hummingbird (Heliodoxa jacula).  The flowers of the Blood of Christ plant are yellow and red and rather small.  The red spots on the leaves help direct the pollinating Green-crowned Brilliant to the flowers.  

Poor Man's Umbrella (Gunnera insignis).
Irazu Volcano National Park, Costa Rica. 

The underside of Poor Man's Umbrella leaves.
Irazu Volcano National Park, Costa Rica. 
Photo by Diane Coggin

Hiking through a stand of Poor Man's Umbrella.
Irazu Volcano National Park, Costa Rica. 
Photo by Diane Coggin

The paramo is a unique ecosystem found at high altitudes in Costa Rica and other countries of Central and South America.  It is a tropical scrub and grassland above the tree line where endemic plants abound.  At the lower reaches of the paramo on the Irazu Volcano we found (Gunnera insignis). This genus of ancient plants date back to the Cretaceous Era when Tyrannosaurus rex walked the earth. Gunnera is widespread throughout the southern hemisphere and Central America.  Gunnera insignis has giant leaves, some over 4 feet wide, supported by a stout petiole. This gives it the common name Poor Man’s Umbrella.  

Toad's Herb (Eryngium carlinae).
Irazu Volcano National Park, Costa Rica. 

We found other interesting plants on the Irazu Volcano paramo.  Toad’s Herb (Eryngium carlinae) is a member of the Carrot family (Apiaceae). These plants have a long history of medicinal use and are used to treat diabetes, digestive distress and high blood pressure.  

Costa Rican St. John's Wort (Hypericum iruzuense).
Irazu Volcano National Park, Costa Rica. 

Costa Rican St. John’s Wort (Hypericum irazuense) grows only in the paramo habitat in Costa Rica and western Panama.  With its bright yellow flowers and small opposite leaves, Costa Rican St. John’s Wort stands out among the paramo plants.  

Paintbrush (Castilleja irasuensis)
growing on the paramo.
Irazu Volcano National Park, Costa Rica. 

Castilleja irasuensis, Paintbrush, is an endemic plant with bright red flowers, growing on Irazu. This plant belongs to a large genus of more than 200 species that ranges from North and South America to northern Asia.  A field of these plants looks like brushes that have been dipped and are ready to paint. Castilleja irasuensis grows only on the paramo of high mountains in Costa Rica and Panama.  

Pelican Flower (Aristolochia grandiflora).
Heredia, Costa Rica.

An unopened Pelican Flower
that is supposed to resemble a pelican.
Heredia, Costa Rica. 

My favorite plant from Costa Rica was Aristolochia grandiflora or Pelican Flower.  This tropical vine produces one of the largest flowers in the world. Before the flower opens it is said to resemble a pelican, giving the plant its common name.  The 8-inch, heart-shaped flower is white with purple markings.  Aristolochia grandiflora is pollinated by flies and attracts these insects by releasing a smell like rotting flesh.  Even the color of the flower mimics a decaying animal.  When a fly, attracted to the odor and color, enters the tube of the flower it is forced deep inside by downward pointing hairs.  The fly is then trapped inside the flower where it drinks nectar and collects pollen.  The next day the hairs that had trapped the fly collapse allowing the fly to escape and carry the pollen to another Pelican Flower. 

Alfred Russel Wallace, who along with Charles Darwin, proposed the Theory of Natural Selection.  Wallace was a keen observer of tropical botany.  In his book Natural Selection and Topical Nature, he wrote, “Here no one who has any feeling for the magnificent and sublime can be disappointed… the parasitic plants growing on the trunks and branches, the wonderful variety of foliage, the strange fruits and seeds that lie rotting on the ground – taken together surpass description and produce feelings in the beholder of admiration and awe”.  Admiration and awe indeed.

Costa Rican Hummingbirds

Fiery-throated Hummingbird (Panterpe insignis).
Savegre Valley, Costa Rica. 

Hummingbirds abound in superlatives.  They are the smallest of all birds, they have the highest metabolic rate of any warm-blooded animal and they are counted among the most colorful creatures on the planet.  Hummingbirds are found only in the New World.  There are 366 species of hummingbirds, but the United States has only 15 species.  The diversity is much higher in Central and South America with Ecuador hosting an astonishing 132 species. 

As with many birds, the male hummingbirds typically have much brighter plumage than the females.  The males use their brilliantly colored feathers to attract females and warn off other males from their territories.

The color of hummingbird feathers can change before your eyes.  A male hummingbird with a black throat can turn its head and flash a brilliant red.  These changeable colors are not due to pigments but from the fine internal structure of the feathers.  Structural color is caused by light refraction and usually requires viewing from a particular angle to be seen.  This is why hummingbird color seems to appear then disappear just as quickly. 

The brilliant colors we see on hummingbirds is not how the birds see themselves.  Bird’s visual systems can discern all the colors we can see but they can also detect the ultraviolet part of the spectrum.  Humans have three types of color detecting cells in their retina called cones.  One type of cone is sensitive to red, another cone detects green and a third type is tuned to blue wavelengths.  Birds have these three kinds of cones, but they also have a fourth type of cone that detects ultraviolet radiation.  So, birds, including hummingbirds, experience the brilliant colors produced by their feathers in ways we can only imagine, combining the iridescent structural colors with ultraviolet radiation.  

Lesser Violetear (Colibri cyanotus) in a rainshower.
Savegre Valley, Costa Rica.

On a recent trip to Costa Rica, we saw some of these colorful hummingbirds.  One of our stops was Batsu Garden in the Savegre Valley of the Talamanca Mountains.  This garden is planted with hummingbird friendly flowers and feeders.  Here we found the beautiful Lesser Violetear (Colibri cyanotus). These birds are brilliant green with patches of iridescent purple feathers covering their ears.  Lesser Violetears are found high in the mountains of Central America and the Andes of South America.  

Brown Violetear (Colibri delphinae).
Talamanca Mountains, Costa Rica. 

Brown Violetear showing its iridescent green throat patch.
Talamanca Mountains, Costa Rica.

Brown Violetears (Colibri delphinae) are close relatives of Lesser Violetears but with muted brown feathers over most of their bodies and violet on their ears.  But Brown Violetears have a surprise.  When seen at just the right angle their throat feathers flash brilliant green.  Brown Violetears have a similar range to that of Lesser Violetears.  

Female Green-crowned Brilliant (Heliodoxa jacula).
Talamanca Mountains, Costa Rica. 

Green-crowned Brilliants (Heliodoxa jacula) are also found in the mountains of Costa Rica and range south to Colombia and Ecuador.  We saw a nice female with her throat and breast spangled with sparkling green feathers.  

Crowned Woodnymph (Thalurania colombica).
Guayabo National Monument, Costa Rica. 

On the Caribbean side of the mountains, we visited the Guayabo National Monument.  The monument is a pre-Colombian archaeological site with foundations of buildings, aqueducts, roads and tombs. In the rainforest near the ruins, we found a single Crowned Woodnymph (Thalurania colombica).  These dark hummingbirds are violet and bright green. They live throughout most of Central America and south to Ecuador.  

Talamanca Hummingbird (Eugenes spectabilis)
looking dull.
Savegre Valley, Costa Rica.

Talamanca Hummingbird. The same bird as above
showing bright color on its throat.
Savegre Valley, Costa Rica. 

Talamanca Hummingbirds (Eugenes spectabilis) are restricted to the mountains of Costa Rica and western Panama, and we saw them throughout the highlands.  It is one of the largest hummingbirds in Central America.  Talamanca Hummingbirds have green bodies and their heads and throats appear black. But if the bird turns its head in just the right way the throat flashes blue and the crown of the head purple.  The Talamanca Hummingbird was once classified as a subspecies of the Magnificent Hummingbird.  This species was split in 2017 into Rivoli’s Hummingbird that ranges from Nicaragua to the mountains of southern Arizona, and the Talamanca Hummingbird.  You can truly say the Talamanca Hummingbird was magnificent.   

Fiery-throated Hummingbird showing
relatively subdued colors.
Savegre Valley, Costa Rica. 

Fiery-throated Hummingbird flashing
brilliant, iridescent colors on its throat and crown.
Savegre Valley, Costa Rica. 

Perhaps the most spectacular hummer we encountered was the Fiery-throated Hummingbird (Panterpe insignis).  This green hummingbird looks rather plain until turns its head and looks directly at you.  Then the throat lights up blue, gold, orange and green while the crown of the head flashes purple.  The Fiery-throated Hummingbird is another species restricted to the higher elevations of eastern Costa Rica and western Panama. 

Hummingbirds are tiny avian jewels.  With their stunning speed, superhero senses and brilliant flashes of color, hummingbirds dazzle wherever we encounter them.  At our home in North Carolina, we are lucky to have a single species, the Ruby-throated Hummingbird (Archilochus colubris). But going south to the tropics we experienced some of the stunning diversity of hummingbirds.    

Thanks to Paul, Amanda and Richard Laurent of Epic Nature Tours for planning and leading us on this wonderful trip to see the bird life of Costa Rica.

Insects Encounters in Costa Rica

 

Reticulated Lubber Grasshopper (Romalea reticulata).  
The small, nonfunctional wings identify this grasshopper as a nymph.
Turrialba, Costa Rica. 

The tropics are renowned for their biodiversity.  Astonishing forms of plant life, dazzling birds and remarkable mammals are overwhelmed by the sheer variety of insects.  Insects exhibit an astonishing range of sizes, shapes, colors and show amazing behaviors.  Costa Rica, a country about the size of West Virginia, is estimated to have over 250,000 species of insects.  We recently visited Costa Rica on a bird watching trip led by Epic Nature Tours.  Even though birds were our main interest we were constantly drawn to the beauty and drama of the insect life. 

Stick Insect (Trychopeplus laciniatus) blending into
a mossy background.
Guayabo National Monument, Costa Rica. 

Trychopeplus laciniatus in the hand.
Guayabo National Monument, Costa Rica. 

One day while hiking in a rainforest our guide pointed to a tree trunk covered with mosses and lichens.  There crawling slowly over these tiny plants was a barely visible walking stick Trychopeplus laciniatus.  This stick insect is green with mossy decorations on its body and legs that allow it to blend perfectly with the background vegetation.  Trychopeplus laciniatus feeds on leaves, particularly those of epiphytic orchids and uses its amazing camouflage to hide from predators. 

Leaf Cutter Ants (Atta sp.)
Turrialba, Costa Rica. 

Winged queen Leaf Cutter Ant.
Savegre Valley, Costa Rica. 

Leaf Cutter Ants (Atta sp.) are among the most abundant insects in Costa Rica.  We constantly saw them marching along their well cleared trails, holding pieces of leaves over their head.  These ants live in huge colonies with populations of up to 8 million.  A single queen is the mother to all these ants. New colonies are established when a winged virgin queen takes her nuptial flight.  She mates with winged males and stores enough sperm to populate a new colony that could thrive for years. 

Video of Leaf Cutter Ants walking along their trail. 

Turrialba, Costa Rica. 

Video by Diane Coggin. 

Leaf Cutter Ants do not eat the leaves they cut.  The ants carry leaf fragments to their underground colony.  There the Leaf Cutter Ants chew the leaves and inoculate them with a fungus that is the sole food for the ant colony.  The ant and the fungus have a mutualistic relationship with the ants providing the fungus with nutrients (leaves) and the fungus giving ants their food supply.  There are 18 species of Leaf Cutter Ants in the genus Atta.  All are found in the New World and each cultivates its own species of fungus. The ant-fungus relationship is considered a form of agriculture and has been going on for over 50 million years, vastly longer than human cultivation of crops. Neither ant nor fungus can survive without the other.     

Female Aloeus Ox Beetle (Strategus aloeus). 
Turrialba, Costa Rica. 

Female Aloeus Ox Beetle. 
Turrialba, Costa Rica. 

Beetles are the most abundant of all the insects and we encountered some of this beetle diversity on our travels.  The Aloeus Ox Beetle (Strategus aloeus) is impressively large and dark.  The males have three horns they use for fighting while females lack large horns.  The larva of the beetle live underground and feed on the roots of plants.  Adult Aloeus Ox Beetles eat mainly flowers and fruit. 

Isotes sexpuncta.
Savegre Valley, Costa Rica. 

While hiking in the cloud forest of Savegre Valley we found a small orange beetle with black spots (Isotes sexpuncta)  sitting on a leaf.  This beetle is found only the the highlands of Costa Rica and belongs to a group called skeletonizing leaf beetles.  These beetles eat the soft tissue of leaves and leave behind only the leaf veins, the skeleton.  

Soldier Beetle (Chauliognathus sp.).
Tapanti National Park, Costa Rica. 

Another attention-grabbing beetle was a black and yellow Soldier Beetle (Chauliognathus sp).  These large beetles, with their bold color pattern were advertising their unpalatability to predators. 

Reticulate Lubber Grasshopper.
This is an adult identified by its wings. 
Turrialba, Costa Rica.

We found Reticulate Lubber Grasshoppers (Romalea reticulata) eating grass leaves on the slopes of the Turrialba Volcano. These grasshoppers are impressively large (over 3 inches long) and black with purple markings on the wings, legs and body.    

Tarantula Hawk (Pepsis sp.).
Lankester Botanical Garden, Costa Rica. 

The most dramatic insect interaction we saw involved a Tarantula hawk (Pepsis sp.). This large wasp has a black body, orange wings and yellow antennae.  The Tarantula Hawk was hunting the even larger Red-thighed Bromeliad Spider (Cupiennius coccineus).  This dangerous pair of arthropods faced off in a duel to the death on the peaceful grounds of the Lankester Botanical Garden in Cartago.  As an adult, the Tarantula Hawk feeds on nectar but causes searing pain if you are stung.  In fact, it is rated a 4 on the Schmidt Pain Index.  Dr. Justin Schmidt spent his career studying bites and stings from arthropods. This dedication to his research included allowing these animals to bite and sting him.  The Schmidt Pain Index runs from 0 (no effect on humans), to 2 (bee sting), to 4 (excruciating).  Only two insects are rated as a 4 on the index and the Tarantula Hawk is one.  Dr. Schmidt described the sting of a Tarantula Hawk as “Blinding, fierce, shockingly electric. A running hair dryer has been dropped in your bubble bath.” 

Red-thighed Bromeliad Spider (Cupiennius coccinea).
Lankester Botanical Garden, Costa Rica. 

The spider in this drama, a Red-thighed Bromeliad Spider, had a leg-span of about three inches and was hunting across a lawn.  These spiders can also deliver a painful bite but nothing like the pain of a Tarantula Hawk sting.  As the spider was walking the low-flying Tarantula Hawk spotted it.  The wasp made repeated attacks.  The spider would rare up, showing its fangs and waving its front legs, but the Tarantula Hawk would fly around to the side or back of the spider.  Then the wasp was able to deliver a sting to the spider.  Within moments, the powerful neurotoxins paralyzed the Red-thighed Bromeliad Spider.  The wasp then began to drag the spider across the ground. We followed the Tarantula Hawk for over 100 feet before we had to leave.  The Botanical Garden was closing and staff would not wait for us to watch the end of the encounter.  The fate of that Red-thighed Bromeliad Spider was to be paralyzed and buried alive, with a Tarantula Hawk egg attached.  After the egg hatched, the wasp larva would eat the spider alive, consuming the nonvital parts first.  After several weeks of development an adult Tarantula Hawk would emerge and begin its spider hunt.    

Tarantula Hawk hovering over Red-thighed Bromeliad Spider.
Lankester Botanical Garden, Costa Rica. 

Tarantula Hawk stinging Red-thighed Bromeliad Spider.
Lankester Botanical Garden, Costa Rica.

Tarantula Hawk dragging paralyzed
Red-thighed Bromeliad Spider.
Lankester Botanical Garden, Costa Rica. 

The tropics exhibit a dazzling diversity of insects.  On our trip to Costa Rica we saw just a handful of the country’s insect marvels. Sitting at home and recounting these encounters makes me think of the small wonders and the life-and-death struggles that play out in the tropics. 

The Mallard Continuum

 

Male Mallard (Anas platyrhynchos).
Rowan County, North Carolina. 

Mallards (Anas platyrhynchos) are the ducks that people think of when they think of ducks.  Mallards are large ducks with a wingspan of about 3 feet and weigh about 3 pounds. Males have an iridescent green head, a white collar and maroon breast.  Females have a more muted color pattern of mottled brown with an eye stripe.  Males Mallards have a yellow beak with a black tip and females have a brown beak. Both male and female Mallards have a bright patch of iridescent blue feathers on the wing called a speculum.  The speculum has white borders and is visible when the ducks are in flight but is harder to see when they are not airborne.  Mallards also have white on their tail feathers. 

Female and male Mallards.
Buncombe County, North Carolina. 

Female Mallards give the classic quack call while males have a quiet, raspy call. They belong to a group of ducks called dabblers because they feed in shallow water by tipping their tails in the air and collecting plants and small animals from the bottom with their beaks.  Mallards are native to most of the northern hemisphere and have been introduced to many locations in the southern hemisphere. 

Male and female Mallards feeding.
Buncombe County, North Carolina. 

                                             

Video of Mallards mating. 
Rowan County, North Carolina.

While male Mallards are unmistakable, females Mallards look very similar to other species of ducks,  in the genus Anas, including the males.  American Black Ducks (Anas rubripes), Mottled Ducks (Anas fulvigula) and Mexican Ducks (Anas diazi) all strongly resemble female Mallards.

American Black Duck (Anas rubripes) in flight.
This duck's dark body, lighter head and violet speculum are all visible.
Alligator River, National Wildlife Refuge, Dare County, North Carolina. 

American Black Duck in flight showing white undersides of wings.
Alligator River National Wildlife Refuge, Dare County, North Carolina. 

American Black Ducks are widespread in eastern North America.  They breed from northern Canada and the upper Midwest and down to North Carolina.  The northern-most America Black Ducks migrate in winter and can be found as far south as the gulf coast from Louisiana to north Florida. America Black Ducks look like very dark female Mallards.  Their heads are lighter than the body, the undersides of the wings are white, and the speculum is violet.  American Black Ducks are the largest ducks in the genus Anas and readily produce fertile hybrids with Mallards.  

Female and male Mottled Ducks (Anas fulvigula). 
West Delray Regional Park, Palm Beach County, Florida.

Mottled Duck showing iridescent blue speculum.
Green Cay Wetlands, Palm Beach County, Florida. 

Mottled Duck.
Green Cay Wetlands, Palm Beach County, North Carolina.  

Mottled Ducks are found throughout much of Florida and north along the Atlantic coast to South Carolina.  A separate subspecies of Mottled Duck ranges from coastal Alabama to Texas and northern Mexico.  Mottled ducks are a little lighter than American Black Ducks but darker than female Mallards.  They have a blue speculum and male Mottled Ducks have a yellow bill while females have greenish bills.  Both males and females have a black spot at the hinge of the bill.  Mottled Ducks also readily produce fertile hybrids from mating with Mallards.

 

Mexican Duck (Anas diazi) displaying its blue speculum.
Willcox Playa, Cochise County, Arizona.

Mexican Ducks range through much of Mexico but can also be found near the border from Texas to Arizona.  They are very similar in appearance to female Mallards but lack white tail feathers and the white border on the speculum is narrower than on the Mallard.  Like American Black Ducks and Mottled Ducks, Mexican Ducks can hybridize with Mallards.

Female and male Mallards.
Rowan County, North Carolina. 

Why do all these ducks look like female Mallards?  All four of these species are closely related. The evolutionary ancestor of this whole group probably looked like the female Mallards of today.  Genetic studies tell us Mottled Ducks diverged from Mallards about 390,000 years ago, Mexican Ducks became a distinct species about 325,000 years ago, and Black Ducks and Mallards separated only 180,000 years ago. While these are long stretches of time, they are but an instant in evolutionary history.  These ducks are all still in the process of becoming genetically isolated from each other.  

Male Mallard
Rowan County, North Carolina. 

Another question is why the males and females of Mottled Ducks, Black Ducks and Mexican Ducks look similar, but in Mallards the males and females look dramatically different.  For some reason, in the Mallard line, the females favored flashily colored males.  Over time a process called sexual selection produced the extravagant males we see today.  Why this has not happened in other ducks of the Mallard continuum is a mystery.