Streptanthus bracteatus is endangered by development, deer browsing, and perhaps habitat loss due to increasing woody plant cover. Reintroduction efforts are being initiated by a team of Austin biologists; Norma Fowler and Karen Alofs are members.
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.
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. Biological Invasions. Abstract
Gabbard, B. L. 2003. The population dynamics and distribution of the exotic grass, Bothriochloa ischaemum. Ph.D. dissertation, University of Texas at Austin.
Effects of white-tailed deer on native plants
