Botanizing

For centuries, people who studied plants were classically trained botanists.  They characterized plant species and classified them by minute details in morphology, down the lengths of leaves, flowers, petioles and bud scales. From these observations, they built a taxonomic system for plants to categorize botanical diversity.  Such descriptions are still used today especially in the ornamental plant industry, where they are valuable for drafting patents to legally protect an organization's product. Classical botanists have also left their mark on the English language, giving us with a wealth of adjectives such as tomentose, hirsute, and pubescent: all referring to various textures of hair. Botanists of bygone eras would probably agree that it is a treat to immerse yourself in natural places and, while a lot of work, rewarding to critically observe them.  Luckily Rhododendron viscosum occurs in a variety of habitats.  Among populations within close proximity, habitats are similar with common vegetation and animal life. The plants within populations share common features like leaf shape, plant height, and environments in which they grow.  Traits that are not shared are things like flower color, which can vary greatly within a population. The majority of R. viscosum populations have white flowers, although some populations contained varying hues of pink.  The picture on top is from a population in southwest Arkansas, while the one below is from central Louisiana.  Note the different shades of white/pink, as well as the subtle changes in stigma arc between specimens.

An observation to add about flowering would be that within populations, all plants flower at different times.  Generally when I begin work on an area the plants are in all flowering stages: from not blooming to past blooming.  This is an important phenomenon because it will limit the amount of gene flow within populations as plants that are not blooming cannot cross with those that are.  A property like this would manifest itself in higher genetic variation at the within population level due to the mating of subgroups and variability for the trait in geographically close groups (See previous post).  

Another physical difference is in plant height and habit.  Again, quite variable when looking at different environments but the traits are conserved within populations, unlike flower color and blooming time.  I have not seen any large differences within populations, but comparing regions tells a different story.  Below are representative plant habits from three populations: southwestern AR (upper), Florida panhandle (middle), and eastern Texas (bottom).  

The plants in southwestern Arkansas along the Oklahoma border were the largest in size, with mature plants easily reaching 10 feet in height. The Texas plants were unique as mature plants were short, only reaching about 4 feet at maturity and tended to sucker a lot. The Florida panhandle populations were the most morphologically distinct, having notably smaller and stiffer leaves on compact plants. A first suspicion is that some of these differences are products of the environments the plants have been growing in:

Rich Mountain summit, Southeastern Oklahoma looking into Arkansas.  A large R. viscosum is located at the base of the ridge's north slope near a stream at ~1,700 feet in elevation.  The forest is open, moist, and dominated by northern and southern hardwoods, notably Northern Red Oak (Quercus rubra), Sweetgum (Liquidambar styraciflua), and Red Maple (Acer rubrum). 

In contrast, the environment near Sopchoppy, FL at ~20 feet in elevation and 1 mile from tidal estuaries.  This is a slash pine (Pinus elliottii) ecosystem, with the dominant understory shrubs being Saw palmetto (Serenoa repens), Titi (Cyrilla racemiflora), and Rhododendron viscosum. In comparison to the photo above, R. viscosum occurs here in full sun under extremely hot conditions.  Plant leaves were smaller and much stiffer, likely an evolutionary response to minimize water loss due to heat or saline breezes off the gulf.  The horseflies here came in swarms of 2 inch awfulness.

R. viscosum in habitat at Boykin Springs, TX.  The populations occurred along seeps in  Longleaf Pine (Pinus palustris) ecosystems.  These have historically been fire dependent ecosystems, and with burnings repeatedly scorching the populations.  The burnt azaleas are the brown foliage in the picture.  R. viscosum is a suckering plant here: quickly sending up new shoots after a fire.  It has colonized large parts of the understory near these seeps with Sweetbay (Magnolia virginiana). Locals in Texas and Louisiana have even given a name to this unique assemblage, where it is known as "Baygall" .

Now to link this all together, you might be wondering how these plants could possibly look so different over these environments.  Part of it could be environmental, where the weather in a given year or set of years might influence plant flowering or leaf shape.  The best example would be fire: plants frequently will be shorter and more likely to sucker.  But what if we removed the environmental differences? By growing the cuttings of these plants I've been harvesting in a common environment (ie. greenhouse), we can accurately document these morphological features without the confounding factors of weather, day length, or fire present in the wild.  If these differences are still present, genetics likely plays a role and we can refine our study with tools previously described. We then blend the worlds of classical botany with modern science.  Without the new technology our understanding will never be as thorough but, without the old knowledge, our understanding will never be guided into the right places.  

I sat for an hour in a Texas forest to witness the dirty deed-a butterfly pollinating R. viscosum. With incredibly sticky pollen carried by insects, it is likely that part of the phenotypic variation observed is due to reproductive isolation between populations.  

An update on the current collections. Subtropical forest in central Florida dominated by old growth Cabbage Palm (Sabal palmetto).  Seedlings of this and other Sabal species are making collection difficult as they shroud out any other undergrowth.

Walking the streams is the quickest way through the forest.

Some people like sunsets or sunrises, but I've always been a zenith guy.  The sun and blue sky at these latitudes are intense! Ocala NF.