How do isolated populations of plants become distributed across the landscape? 130 species of Midland County plants are found at a handful of locations in the county in our two Aeolian (wind deposited) habitats. There are only four salinas in Midland, and the loess on the north and east sides of each are adorned (in wetter years) with species of plants that are adapted to the high pH of the soils. These salt lakes are scattered across southeastern Midland County and the closest together are over 5 miles apart.
Shinoak and sandsage are plants found only in very sandy soils. In Midland County, the species are only found along the north sides of the draws at specific locations. The nearest shinoak population is twenty miles north. The three shinoak areas have differing populations of other species of plants. The northernmost population is the only one to have western wallflower, while the southwestern most is the only one to have bullnettle.
There are only two locations in the county for several species of plants that prefer rocky limestone bedrock. One of these locations is artificial, and several species appeared (within 15 years) at the location after a channel was dug through the outcropping of limestone. The locations are over 20 miles apart.
The obvious answer for the plants being spread to specific sites that meet their needs is that wind blew their seeds to the location. That is probably true for the species with seeds as small as dust particles, but not true for the shinoak, bullnettle, and others with large seeds. Shinoak and bullnettle seeds are eaten by animals, but the seed is not passed through the digestive system as a whole in a condition to germinate.
Bullnettle seeds have a seedpod with barbs, so it could travel in the hair of an animal, but strangely enough, it only lives at one location in Midland county, and in the dunes around Monahans, but north of the dunes near Jal, New Mexico. (Sanddunes extend all the way to Fort Sumner west of the Llano Estacado.) This limited range indicates it rarely travels in the fur of an animal. (The barbs on the leaves and seeds of the bullnettle plants exude a liquid that causes blisters or welts to form on the skin of humans.) Bullnettle also grows along the Brazos watershed near Jayton, 100 miles northeast.
The question that begins this essay might not capture everyone's imagination as it does the mind of a field botanist. Here on the Llano Estacado we live in the ecotone between the arid West and the humid East. We live where eastern and western species meet (or possibly where their differences are developed and speciation occurs.) Isolated populations of species from much further west and much further east occur at surprising places far removed from where they are common.
Field botanists love to explore property that they have not visited before -- or where other field botanists have not explored. Very little of the Llano Estacado (and the surrounding areas such as the breaks and canyons or the sanddune country) has been surveyed by academic botanists. Academic botanists focus (in modern times) on matters of microscopic physiology and genetic differences, and rarely maintain long-range studies of populations of plants in specific locales. Taxonomy is an almost forgotten art, except when geneticists do chromosome counts.
Field botanists are usually avocational enthusiasts or xeriscape plant growers, like myself. Over the years I have had the pleasure of meeting others. One, Steve Nelle, works for the NRCS (National Resource Conservation Service) in San Angelo. Another Is Michael Eason, who works for the Ladybird Johnson National Wildflower Center but lives in Alpine. Others are Steve Lewis who owns Native Ornamentals Nursery in Mertzon, and Patty Manning, who runs the greenhouse at Sul Ross University in Alpine. Recently I met Russ Kleinmann, a retired surgeon, who has created a fabulous website of the flora of the Gila Wilderness area in southwestern New Mexico. I first "met" him on Facebook, but he visited the Sibley Nature Center on vacation this spring. Facebook has connected me with other field botanists across the west, as well.
Since modern civilized society puts little value in ensuring that people know anything about their home landscape, we field botanists feel like bold explorers, going where few (if any) have gone before. We explore our home ecoregion and find countless wonders!