Endangered species: Streptanthus bracteatus
The annual wildflower Streptanthus bracteatus is endangered by land development, by recreational use of public land, and by deer browsing.
Zippin, D. Z. 1997. Herbivory and the population biology of a rare annual plant, the bracted twistflower (Streptanthus bracteatus). Ph.D. dissertation, University of Texas at Austin.
A recent project found that increasing canopy cover in Travis County woodlands is making the habitat less suitable for this species. Fowler 2010. Final Report to TWPD and USFWS.
Invasive non-native species: Bothriochloa ischaemum
Bothriochloa ischaemum, King Ranch bluestem, is a perennial Eurasian grass that reduces diversity in central Texas savannas and sometimes forms near-monocultures. A field survey found it to be absent only from sites with woody plant canopy. It is more common along roads, but its distribution is unrelated to fire or grazing intensity.
Gabbard, B. L., and N. L. Fowler. 2006. Wide ecological amplitude of a diversity-reducing invasive grass. Abstract
In a garden experiment at Brackenridge Field Laboratory it out-competed the largest common native grass, Schizachyrium scoparium (lower image on right).
Invasive native species: Juniperus ashei
false color aerial, showing plot
Endangered species: Physaria thamnophila (Zapata bladderpod)
The endangered Zapata bladderpod (Brassicaceae / mustard family) lives near the Rio Grande. Threats include development, habitat conversion to grassland for ranching, invasive grasses, and the border wall. With collaborators Chris Best (USFWS), Dana Price (TPWD), and Alice Hempel (TAMU-Kingsville), we found that it performs best in open shrubby vegetation. Pictures taken by C. Best.
Fowler, N. L., C. F. Best, D. M. Price, and A. L.
Hempel.Ecological
requirements of an endangered Tamaulipan thornscrub plant. in press,
Southwestern Naturalist.
