Saturday, December 12, 2015

Likin' Lichens

A fruticose Slender Orange Bush Lichen, Teloschistes exilis, makes
its home among various foliose lichens.

What lies beneath our feet and in front of our eyes, typically small and unassuming, sometimes brightly colored, but always waiting patiently for their contributions to take hold?  Lichens! Composite organisms made up of a fungus and a photosynthetic partner, most commonly an algae, lichens are ecosystem pioneers.  They break down rock surfaces and prepare areas for mosses, grasses, and trees to follow.  Certain species that also contain cyanobacteria can improve the fertility of the soil by adding necessary, usable nitrogen, and many species are used as bio-indicators of air quality.  They are also highly efficient collectors of airborne substances, and recycle these substances into the soil.  Historical uses for lichens include food, natural dyes, and herbal remedies. 

Mexican Yolk Lichen, Candelina submexicana, is a good example of a crustose lichen.

Lichens can be observed in many places, including on the ground, on rocks, and on trees.  The surface, or substrate, on which they are found provides a place for them to attach and grow.  Some species are substrate-specific while others can grow on a wide variety of substrates.  Ground substrates can include sand, soil, mosses, and downed decomposing logs.  These lichens act as soil stabilizers and contribute to soil fertility.  Rock substrates include natural substances like cliffs, talus slopes, boulders, and pebbles, and man-made substances such as concrete and roof shingles.  Lichens on rock substrates often colonize the rock and act as decomposers, turning it into soil.  Tree substrates include both deciduous trees such as oaks and conifers such as firs, cypresses, junipers, and pines.  Older trees often have a greater diversity of lichens, partly due to a more fissured bark that has a specific texture, chemistry, and moisture-holding capacity.  

Cumberland Rock-shield Lichen, Xanthoparmelia cumberlandia, is a type of foliose lichen. 

Lichens are mostly commonly divided into three growth forms: crustose, foliose, and fruticose. Crustose lichens look like they are spray-painted on their substrate, and their lower surface or ‘medulla’ is the same color as and blends into that substrate.  Foliose lichens are leafy growths with distinct lobes, and their medulla is a different color.  Fruticose lichens are often bushy or shrubby growths, and can be highly variable.  They often form obvious disk or cup-shaped structures called ‘apothecia.’  

Western Antler Lichen, Pseudodevernia intensa,
is a fruticose lichen.
Sundew Beard Lichen, Usnea cirrosa, shows
off its apothecia.

As composite organisms, lichens have been used worldwide as indicators of air quality.  They are very sensitive to the presence of low levels of sulfur, nitrogen, and fluorine-containing pollutants that adversely affect their community composition, growth rates, reproduction, biomechanics, and appearance.  By concentrating a wide variety of pollutants in their tissues, they act as pollution monitors, and are the subjects of many biomonitoring studies regarding air quality and climate change being conducted jointly by the U.S. Forest Service and the Environmental Protection Agency.  Since lichens are long-lived, can be observed in the field in any season, and with many species having extensive geographical ranges, they allow for changes in pollution to be studied over large areas and long periods of time.

As you can see, the lichen has almost all it needs to survive.   While most species of lichens grow very slowly, they all require a proper substrate, clean air, moisture, sunlight, and warmth to thrive. Turning air into life, they are truly one of nature’s alchemists!

Wednesday, November 18, 2015

The Seven-faced Bird

Most often, the traditional star of holiday meals in the United States is the domestic turkey. Interestingly, this bird is only one of two wild bird species native to North America (the other is Muscovy Duck) that have been bred specifically for human consumption.  Wild turkeys (Meleagris gallopavo) were first domesticated in Mexico, and then exported to Europe.  European settlers brought domesticated turkeys back to the New World, but would also hunt the wild birds they found.  Currently, there are more than 7 million wild turkeys in North America, a pretty astounding fact when they were almost extinct by the 1930s due to overhunting and deforestation of their preferred habitat.

Adult wild turkeys are large birds with long reddish-yellow to grayish-green legs, with each foot having three toes in front and a shorter, rear-facing toe in back.  Their body feathers are generally blackish to dark brown, with a coppery sheen that becomes more pronounced in mature males. The toms or gobblers, as the males are called, have a large, featherless, reddish head, red throat, and red wattles on both the throat and neck.  The long, fleshy object hanging over the male's beak is called a ‘snood’, and the tail feathers are all one length.  Juvenile males are called jakes, and they have shorter wattles and a tail fan with longer feathers in the middle.  Males also have a spur behind each of their lower legs, which they use when fighting.  Wild turkeys show a strong sexual dimorphism, with the males being significantly larger than the females or hens.  The hens have duller feathers overall, mainly in shades of brown and gray.  Young females are called jennies, and the very young of both sexes are called poults.

In Japanese and Korean, the turkey is called 'shichimencho' and 'chilmyeonjo' respectively, both of which translate to 'seven-faced bird.'  This reflects the ability of the male wild turkey to change the color of its facial skin and wattles in a matter of seconds due to excitement or emotion.  While the birds' head color can range from red to pink to white to blue, certain changes represent certain moods.  When the male is excited his head turns blue, and when he is ready to fight it turns red. 

Unlike their domestic counterparts and despite their weight, wild turkeys are agile fliers.  While their powerful legs can get them running up to 25 mph, their top speed in flight is 55 mph. In their ideal habitat of open woodland or wooded grasslands, they fly beneath the canopy top and sleep up in trees.  They can live an average of 3-5 years in the wild, eating a varied diet that includes grains, insects, berries, and even small reptiles.  Their daytime vision is three times better than a human's and they see in color, but they have poor vision at night.    

There are 6 different subspecies of wild turkey in North America, showing differences in coloration, habitat, and behavior.  In our region, the Rio Grande Wild Turkey (M. g. intermedia) is dominant, naturally ranging through Texas to Oklahoma, Kansas, New Mexico, Colorado, and Oregon. Having slightly longer legs than other subspecies, it is better adapted to a prairie habitat, with a more greenish-coppery sheen and buff-colored feathers on the tail tips and lower back.  This subspecies prefers brushy areas near streams or rivers, and forests of scrub oak, pine, and mesquite.

Either way you slice it, as you celebrate the holidays this year, reflect on the wonders of the 'seven-faced bird,' appreciate their history with humans, and keep an eye out for wild wattle and snood!

Sunday, November 1, 2015

Gone to Seed

Scarlet Leatherflower, Clematis texensis

Often used as an informal figure of speech meaning to deteriorate or go downhill, ‘gone to seed’ can have a negative connotation.  But each seed contains a new beginning: a tiny plant just waiting for the right conditions such as water, warmth, and a good location, to germinate and grow.  Seeds and seed heads form fascinating shapes, varying sizes, and intricate patterns, often adorning the fall and winter landscape.

Illinois Bundleflower, Desmanthus illinoensis

Inland Sea Oats, Chasmanthium latifolium

Plants have many ways of dispersing their seeds, and most have evolved over millions of years. While the methods are tried and true, certain seeds have developed in very particular ways to take advantage of such methods, and some plants only release their seeds in response to specific triggers. 

Wafer Ash, Ptelea trifoliata

Texas Milkweed, Asclepias texana

Wind helps seeds float or flutter away, often aided by seed structures such as thin wing extensions or long, feathery tails like those on the endemic Scarlet Clematis (Clematis texensis).  Texas Bluebonnets (Lupinus sp.) employ the expulsion or explosion method, where the small, pebble-like seeds are forcibly expelled when the dried pods twist open in the warm sun.  Gravity plays a part in many plants seed dispersals, where weighty seeds fall off the plant and roll to a new location.  The best example of this are the round, heavy fruits that simply fall off a plant when ripe, such as those on Mexican Plum (Prunus mexicana) or Texas Persimmon (Diospyros texana).  If the fruits have a tough outer shell, they may travel some distance from the parent plant, and if they have a soft skin, they may break open where they fall and scatter the seed or seeds within. 

Texas Persimmon, Diospyros texana

Mexican Buckeye, Ungnadia speciosa

Some plants produce very light seeds, seeds with buoyant fluff, or seeds with air trapped in them, so they can float away from the parent plant that grows in or around water, like Common Buttonbush (Cephalanthus occidentalis) or Black Willow (Salix nigra).  Others employ the assistance of animals, which can come in the form of seed or fruit eating (where the seed can pass undigested through the animal), seed caching or burying, or seed transportation.  Often unbeknownst to the animal, seeds can be covered with tiny hooks or spines that catch on a passing animal’s fur, and eventually rubbed off in another location.  Common examples include Cedar Waxwings and American Robins eating juniper and yaupon berries, both ground and tree squirrels eating and caching acorns, and many animals (including humans) that emerge from the wilds carrying the seeds of Beggarsticks (Bidens sp).    

Yaupon, Ilex vomitoria

This fall and winter, let the seeds linger! Not only do they provide much needed food for wildlife, but leaving them allows for some beautiful and mysterious patterns in your winter landscape, and the promise of renewing the cycle of life that begins again each spring!

Tuesday, October 13, 2015

Fields of Gold

Prairie Goldenrod, Solidago nemoralis

Cooler temperatures and shorter days mark the onset of autumn, and the golden colors of the season begin to surround us.  Among the amber and scarlet hues making an appearance in the landscape, one cannot help but notice two of our most common fall-blooming native plants: Goldeneye (Viguiera dentata) and Prairie Goldenrod (Solidago nemoralis).  

Goldeneye, Viguiera dentata

A member of the sunflower family, Goldeneye is a bushy, drought-tolerant, multi-branched plant that tends to grow in colonies, providing rich swaths of golden color along our roadsides and in open areas.  It has narrow leaves and numerous 1.5 inch daisy-like flowers at the tips of long, slender stalks.  Growing to 3 feet tall in full sun or up to 6 feet tall in partial shade, this plant is native not only to Texas but to Arizona and New Mexico as well.  It prefers relatively dry, partially shaded areas such as woodland edges and open prairies, and in Mexico is also known by the common name Chimalacate.  

The mid to late fall blooms of Goldeneye not only provide seasonal color, but provide for native wildlife as well.  Goldeneye is the larval food plant for both the Bordered Patch and Cassius Blue butterflies, and if spent flower stalks are left to stand through most of the winter, they will provide good seed forage for Lesser Goldfinches and other birds.  Infusions of this plant are still used today as an antibacterial treatment for baby rash.  

Prairie Goldenrod, Solidago nemoralis

Prairie Goldenrod, also called Gray Goldenrod, is a slender-stemmed plant 1.5 to 2 feet tall, that blooms from June through October.  A member of the aster family, it has thin, coarsely-toothed leaves and yellow flowers that are borne on the upper side of hairy stalks, arching out and downward to create a vase-shaped flower cluster.  Individual plants bloom at various times, extending the flowering season, but they are most noticeable in fall, especially when paired with purple Gayfeather and red Autumn Sage.  An excellent addition to a wildflower meadow or a sunny garden, Prairie Goldenrod is naturally found in dry, open woods and upland prairies, and does well in full sun to part shade. A carefree plant, it can become invasive if left alone, but is also easily controlled.  

Of special value to bees and butterflies for its pollen and nectar, and to several species of finches for its seeds, Prairie Goldenrod was also used by Native Americans to treat jaundice and kidney disorders, and as a wash for burns and skin ulcers.  The Navajo burned the leaves as incense, and used the seeds for food.

As you wander along roadways and pathways this fall, admire these fields of gold that delight not only our senses, but provide a bountiful harvest for our wild neighbors as well!

Wednesday, September 23, 2015

Blues of Summer

Marine Blue (Leptotes marina)

The gossamer-winged butterflies (or Lycaenidae) are a large family of small butterflies that include the coppers, hairstreaks, and blues.  Usually noticed when flying erratically in an up-and-down fluttering motion, they bask in the sun with their wings open, and when perched sit with their wings closed, often rubbing their hind wings together.  The blues are especially small with a wingspan of about one inch, and while mostly blue above, the identifying field marks are found mainly on the undersides of their wings.  In Central Texas, the most commonly seen blues in open, sunny habitats are the Eastern Tailed-blue, Marine Blue, and Reakirt’s Blue.

Eastern Tailed-blues (Cupido comyntas)

Eastern Tailed-blues (Cupido comyntas) are common and can be identified by the one to three orange spots near the tail on the underside of the hind wing.  The males are deep blue on their uppersides while the females are a lighter blue to brown.  They occur in the eastern half of the United States from the coast to the Great Plains.

Marine Blue (Leptotes marina)

Marine Blue (Leptotes marina)

The Marine Blue (Leptotes marina) is a fast flier (for a blue) and is found from Texas west to Southern California and south to Mexico.  Its’ underside is strongly striped gray-brown often with a pale purple fringe.  The male has a blue upperside with a strong purple overlay, while the female has a brown upperside with some blue at the base of the wings.

Reakirt's Blue (Echinargus isola)

Reakirt's Blue (Echinargus isola) - male

Reakirt's Blue (Echinargus isola- female

While the other blues fly mostly spring to fall, Reakirt’s Blue (Echinargus isola) flies year round in Texas.  The males are lavender-blue above while the females are primarily gray-brown with a touch of blue basally, and they are identified by the conspicuous row of five white-ringed black spots on the underside of their forewings.

Western Pygmy-Blue (Brephidium exilis)
Ceraunus Blue (Hemiargus ceraunus)
Cassius Blue (Leptotes cassius)

Other species that are not common in our area but can sometimes be found include Western Pygmy Blue (Brephidium exilis), Ceraunus Blue (Hemiargus ceraunus), and Cassius Blue (Leptotes cassius). With a wingspan of about half an inch with coppery brown on the underside, the Western Pygmy Blue is the smallest butterfly in North America. Ceraunus Blue and Cassius Blue both have a wingspan of about one inch, and have two submarginal eyespots on the underside of the hindwing (in Florida, the Ceraunus has only one eyespot). They can be distinguished from each other by the patterns on their undersides, with the Ceraunus having a row of dark postmedian dashes on a gray background, and the Cassius having broken pale lines with some white or 'blank' spots on a tan background.

Most of these blues utilize legumes as their larval food plants, so you can often see them flying around plants in this family, including alfalfa, mesquite, clover, dalea, mimosa, and indigo species. The caterpillars of these butterflies are slug-shaped, somewhat flattened, and are often tended to by ants, which feed on the sweet liquids secreted by the larvae and in turn protect the larvae from other predators.  As adult butterflies, they feed on nectar from a variety of herbs found flowering in grasslands, fields, meadows, and along creeksides.

Interestingly, these blues are part of a group of butterflies called the Polyommatus blues, originally studied by the self-taught butterfly expert and famous mid-twentieth century novelist Vladimir Nabokov, who hypothesized that they arrived in the New World from Asia in waves over millions of years.  While few professional scientists took his ideas seriously at the time, recent DNA and gene-sequencing technology has proved him absolutely correct – that this group of butterflies originated in Asia, moved over the Bering Strait at a time when the land was relatively warm 10 million years ago, and eventually headed south all the way to Chile!

Friday, August 21, 2015

Mysterious Migration

Wandering Glider, Pantala flavescens

Fall migration season is upon us, and that usually conjures up thoughts of songbirds and hawks using the central flyway through Texas to make their way south to the subtropics and tropics for the winter.  However, birds are not the only ones who migrate, and while much has been said about the complex, annual migration made by Monarch butterflies, the record for the longest insect migration (twice the distance of the Monarch) belongs to a dragonfly species, the Wandering Glider (Pantala flavescens).  In fact, dragonfly migration has been suspected for over 100 years, and up to 50 of the world's 5,200 dragonfly species are thought to migrate (about 16 out of 326 in North America), but not much is known about where they are coming from or where they are going.  

Green Darner, Anax junius

In Texas, there are several species of dragonflies that migrate in addition to the Wandering Glider. They include the Common Green Darner (Anax junius), Black Saddlebags (Tramea lacerata), Variegated Meadowhawk (Sympetrum corruptum), and Spot-winged Glider (Pantala hymenaea).   Cooler nights seem to trigger the dragonflies' journey south, and like birds, they build up their fat reserves before setting out.  They may use the lay of the land as a navigation guide, and some scientists speculate that they have an internal magnetic compass, as those that fly off course and out to sea appear to realize their mistake and reorient themselves.  

Black Saddlebags, Tramea lacerata

Dragonflies migrate during daylight hours, and green darners have been found to break their journeys every three days to rest and feed, using oak and juniper trees as stopover sites.  Like monarchs, the full migration circuit takes multiple generations to complete, as it is the offspring of the generation that traveled south in the fall that is migrating north again in the spring.  

Variegated Meadowhawk, Sympetrum corruptum

Swarms of dragonflies can create one of nature's most impressive spectacles, with tens to hundreds of thousands of individuals streaming southward along lakeshores, mountain ridges, and coastlines.  Even with the origins and destinations poorly known, the migration in the fall is more noticeable than that in the spring, presumably because the spring event occurs over a wider front and a longer period of time.  However, migration is the only explanation for how dragonfly adults appear in early spring in places where their nymphs or larvae from the previous year or years have not yet emerged.

Spot-winged Glider, Pantala hymenaea

The ecological role of migrating dragonflies is another facet of the mystery yet to be resolved. Since several species use the same migration strategies and timing as migratory birds, traveling at the same times and concentrating in the same places, it is likely that certain bird species are exploiting the abundance of dragonflies as a source of fuel for their own migration.  More research is being done to solve these mysteries, most notably the Xerces Society’s Migratory Dragonfly Partnership initiative, which uses “research, citizen science, education, and outreach to understand North American dragonfly migration and promote conservation.”    

Sunday, August 9, 2015

Traveling Tarantulas

Relatively common throughout Texas, the Tarantula (Aphonopelma sp.) is Texas’ heaviest and largest spider.  Typically, the head and legs are dark brown, and the abdomen is brownish-black. Coloration varies between individuals as well as between the 14 different species found in Texas. Identification of individual species is difficult, however, and is often performed only on mature males under a microscope.

Tarantulas are typically found in grasslands and semi-open areas, and use burrows, natural cavities under stones or fallen logs, spaces under loose tree bark, and even old rodent holes as shelters.  They are also capable of digging their own burrows, and often line them with webbing, placing a few strands across the front to help detect passing prey.  Laying several hundred eggs in a hammock-like web constructed inside the burrow, females will guard them until they hatch. Females have lived in captivity for over 25 years, while males rarely live over two or three months after reaching maturity.   
Like many animals, tarantulas molt their exoskeletons several times as they grow.  The skin on the hard upper shell and abdomen splits, and the tarantula begins the process of squeezing through the opening.  Most of the time, tarantulas molt while positioned on their backs, twitching, stretching, and kicking until the entire exoskeleton has been cast off.  After they have wriggled free of their old skin, this discarded exoskeleton is a perfect replica of the spider, minus its head and fangs. 

Other insects such as crickets, beetles, grasshoppers, cicadas, and caterpillars form the basic diet of the tarantula.  They inject their prey with a poison when they bite, which liquefies the prey’s insides, making it easier to ingest.  While they can climb, they are usually restricted to the ground, where the majority of their prey is found.  The hairiness and large size of tarantulas often evokes concern, but the bites of Texas species are not serious to humans.  Tarantulas maneuver quickly to face whatever disturbs them, often raising up on their hind legs and stretching out their front legs in a threatening posture.  They have also been observed rapidly brushing the top of their abdomen with their hind legs to dislodge hairs that can be used to irritate the attacker’s eyes or skin.

For a few weeks late in the summer or early fall, one of the most spectacular spider events occurs in Texas.  Not well understood, this phenomenon is often called a migration, but it may be related more to mating rather than seasonally motivated movement.  Males actively wander to seek out females, and can travel 50 miles in search of a mate.  Populations seem to follow a boom and bust cycle, depending on weather patterns and the availability of food, but a good year can be a sight to behold if summer rains have been plentiful.  While the males are out searching, females wait in their burrows for a suitor to appear.  Larger and more robust, the female does not always accept any male that comes along, and will kill and eat males that are deemed unsuitable. 

Tarantula Hawk
As formidable as they may seem, tarantulas are not without their own enemies.  In fact, in late spring and early summer they are routinely hunted by female Tarantula Hawks as food for their larvae.  Belonging to a group of spider wasps in the genera Pepis and Hemipepsis, tarantula hawks are large, 2-inch long wasps with iridescent blue-black bodies and bright, rust-colored wings.  This vivid color combination is a form of aposematism or warning coloration, a type of advertising signal to both predator and prey that these species are potentially harmful.  These wasps have the ability to deliver a powerful sting, and their long legs have hooked claws for grappling their victims.  

Flying low over the ground, the female tarantula hawk will find a tarantula and sting it, which paralyzes the spider but does not kill it.  She then drags the inert tarantula into her burrow or transports it to a specially prepared nest, where she lays a single egg on the spider’s abdomen, then seals the opening to the burrow as she leaves.  When the wasp larva hatches, it creates a small hole and enters the spider’s abdomen, where it feeds voraciously, avoiding vital organs to keep the spider alive as long as possible.  After several weeks the spider dies, the larva pupates, and then it emerges from the spider’s abdomen to continue its lifecycle.