A Closer Look: Conserving Endemic Plant Species in North Texas

How do biologists and land managers determine which properties are highest priority to recommend for conservation? One method could be to focus on protecting the habitats of plants endemic to a particular region in order to save that area’s essential, unique character. 

Classifying an organism as endemic means its naturally occurring distribution is confined to a specific range and is found nowhere else on Earth. Endemic species often arise in microhabitats contained within a larger ecoregion—scattered soil pockets, for example, that differ substantially from the composition of the surrounding area, or seeps / springs in a dry landscape. These microhabitats can contribute extensively to species diversity and are important to include in conservation planning. Endemics can serve to flag these spots as worthy of a closer look. 

The Cross Timbers and Prairies Ecoregion of northern Texas, while not a hotspot of rare and endangered species in Texas, does have several endemics that warrant protection. These hometown stars include white rosinweed (Silphium albiflorum), Engelmann sage (Salvia engelmannii), Glen Rose yucca (Yucca necopina) and Comanche Peak prairie clover (Dalea reverchonii). 

White rosinweed and Engelmann sage are prairie remnant indicators found in the thin, gravelly limestone soil of hilltops and slopes in the Grand Prairie and Lampasas Cut Plain. The beautiful Silphium flowers are an unexpected summer gift, as it typically flowers in June. Walking through a field of Engelmann sage in April releases its exotic scent and fills your senses. Both species have evolved adaptations necessary for thriving in full sun under marginal growing conditions—extensive root systems; and rough / hairy leaves and stems to more efficiently dissipate heat. However, these extensive root systems make attempts to move these plants out of the way of development mostly fruitless. Conserving these plants in place within their habitats is the best course of action. 

Glen Rose yucca has evolved to exploit another of the most inhospitable habitats that our area offers. Much less common than the rosinweed or sage, Y. necopina is at home in deep sandy soil as loose and low in nutrients as beach sand. Despite these challenges, this yucca puts on quite a flowering display in May when the conditions are right. The entire known global range of this plant is limited to ancient river terraces and isolated sand pockets in Hood, Somervell, Parker and Tarrant Counties. More sites could be discovered in the future by further surveying. 

One of the rarest species in our area is the Comanche Peak prairie clover. The original population— discovered in the 19th century on Comanche Peak in Hood County near Granbury—has disappeared; the only known existing populations are in Parker, Wise and Erath Counties. Botanical surveys indicate that this plant is found on a specific type of rocky limestone outcrop—the Walnut Shell Formation—so it’s a very narrow-range endemic. Walnut Shell limestone typically occurs on high ridges which are often prime locations for development. Conserving this species may require finding additional populations via more extensive surveys and identifying appropriate locations for reintroductions, as well as using conservation easements or making outright land purchases from willing sellers. 

Conservationist Aldo Leopold once stated, “To keep every cog and wheel is the first precaution of intelligent tinkering”. Nowhere is this truer than in conservation planning. We must look to endemic plants as the beautiful, hard-working foundation of endangered habitats.