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
RSVP to big-bend-chapter@npsot.org

Description

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.

 

About the Region

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This low-elevations region of Texas extends inland from the barrier islands, about 60 or so miles, and stretches from Brownsville to Louisiana. In total, it covers about 9.5 million acres, with a high point of 150 feet in elevation. More than 1000 species of plants can be found in this region. On the southern end, species more common in Mexico (such as Sabal mexicana) and Central America occur.

The barrier islands provide us with dune systems, and clay flats to the inland side, which have species found in these areas alone. Many plants here, such as Ipomoea pes-caprae (beach morning glory), can be found throughout tropical regions of the globe. I’ve encountered the same species on the beaches of Guam.

Once inland, vast marshes and wet prairies occur. Occasionally, oak (Quercus fusiformis) groves can be found. Common grasses include species of Bothriochloa, Paspalum, and Sporobolus; eastern gamagrass (Tripsacum dactyloides); and switchgrass (Panicum species). Many rivers and creeks cut through the Gulf Prairies, and along these riparian areas various species of trees, Sabal minor, and other plants adapted to clay soils can be found. Due to overgrazing, farming, and fire suppression, woody species such as mesquite (Prosopis glandulosa) and huisache (Acacia farnesiana), and invasive species such as chinaberry (Melia azedarach), Brazilian pepper (Schinus terebinthifolius), and Chinese tallow (Sapium sebiferum) have increased and displaced our native flora.

Source: Wildflowers of Texas by Michael Eason