Big Bend Chapter

Program: Evolution of Plants with Jeff Keeling

[from Karen Little]

Program: Evolution of Plants with Jeff Keeling
Date: Saturday, March 25th, 2023
Time: 10:00 a.m.
Location: Room 201 of the Warnock Science Building at Sul Ross State University
Participation: Open to 60+ participants


Current estimates calculate a wide range of the number of known plant species somewhere between 320,000 and 435,000 (the latter number including many sub-species and varieties elevated to the species level). Given this immense diversity, people tend to classify plants into general, non-specific categories for the sake of convenience, such as ‘trees’, ‘shrubs’, and ‘wildflowers’. Biologists, however, classify plants based on their evolutionary relationships that have been more accurately defined over the past century and are still being updated as new data and evidence emerges. Many of our native plants in the Chihuahuan Desert serve as reference points and an opportunity to illustrate important adaptations in habit and life cycles that have developed in plants throughout geologic history. From microscopic, single-celled algae to multicellular life forms that constitute some of the largest living organisms on our planet, the journey of plant evolution over the past ca.450 million years is one of the planet’s most amazing and transformational processes. The colonization of earth’s land masses by plants gave rise to the terrestrial environments that sustain, not only our species, but the vast biodiversity that underpins the ecological health of our biosphere.

Sul Ross biology lecturer Jeff Keeling will be presenting a PowerPoint presentation that will cover this progression from the basal lineages of the recently expanded “plant” kingdom and the complex life cycles that will eventually give rise to all of the more familiar plants that we observe all around us and are a part of our everyday lives.


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About the Region

New Braunfels, the location of our Fall 2024 Symposium, straddles both the Edwards Plateau Ecoregion and the Blackland Prairie ecoregion. Interstate 35 divides the city of New Braunfels; its path through the city closely parallels the boundary of these two ecoregions, with the Edwards Plateau on the west side and the Blackland Prairies region to the east. The Edwards Plateau area is also called the Hill Country; however, this general term covers a much larger area extending farther north. Spring-fed creeks are found throughout the region; deep limestone canyons, rivers, and lakes (reservoirs) are common. Ashe juniper is perhaps the most common woody species found throughout the region. Additional woody species include various species of oak, with live oak (Quercus fusiformis) being the most common. Sycamores (Platanus occidentalis) and bald cypress (Taxodium distichum) border waterways. This area is well known for its spring wildflower displays, though they may be viewed in spring, late summer, and fall, as well. According to Texas Parks and Wildlife, average annual rainfall in the Edwards Plateau ranges from 15 to 34 inches.

The Blackland Prairie extends from the Red River south to San Antonio, bordered on the west by the Edwards Plateau and the Cross Timbers, and on the east by the Post Oak Savannah. Annual rainfall averages 30 to 40 inches, with higher averages to the east. This region is dominated by prairie species. The most common grass species include little bluestem (Schizachyrium scoparium) and Indian grass (Sorghastrum nutans) in the uplands and switchgrass (Panicum virgatum) in the riparian areas and drainages. Common herbaceous flowering plants include salvias, penstemons, and silphiums. This area has suffered greatly from overgrazing and agricultural use. Few intact areas remain, though many of the plants can be found along county roadsides throughout the region.

Our four host chapters (New Braunfels, Lindheimer, Guadalupe, and the Hill Country chapters) are located in one or both of the ecoregions above. However, the eastern portion of Guadalupe County also falls within the Post Oak Savanna ecoregion. Annual rainfall averages 35 to 45 inches, with higher averages to the east. A wide variety of hardwood trees are found, including several species of oaks, elms, and in the Bastrop area, loblolly pine (Pinus taeda). Grasses and forbs dominate in the open savannas, with most common grass being little bluestem. Ranching, agriculture, and fire suppression have allowed woody species to encroach on the once-open savannas.

Source: Wildflowers of Texas by Michael Eason