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Convolvulaceae
Bonamia ovalifolia is a very attractive herbaceous perennial from a woody crown. Stems are deciduous, dying back to the crowns in November, and re-emerging in April. Leaves are round, about 1 cm in diameter, and are silvery blue-green, on stems that reach 30-40 cm in height. Plants are generally unbranched, with many single stems emerging from a woody crown. They may also be clonal, connected by rhizomes. Flowers are ca 2 cm in diameter, lavender-blue, rotate, and open at the terminal ends of stems in May-June. Fruits are pods or round capsules, containing 4 ovules in early fruit, but developing only 1-2 seeds to maturity in late July. Fruits are surrounded by bracts, which continue to surround them even after fruits break away from plants. Dispersal appears to be facilitated by wind, gravity (seeds rolling downhill), and water from the occasional strong summer rains.
Only 2 populations are known within U.S. boundaries, but there may be more in Mexico. There are undocumented reports of occurrences in Mexico. The habitat is generally on sandy substrates. Both sites are within 50 yards of the Rio Grande River, with one occurring on a steep sandslide located just below a large cave that attracts hikers. The other, smaller population grows in the middle of a flat, sandy wash, on sandbars stabilized by Prosopis and Acacia. Population size is difficult to ascertain, as plants grow in clumps, and without digging between them, it is difficult to determine whether plants are clonal or not. The estimated number of plants at the steep site is ca 200-300. Threats at this site include trampling by hikers trying to get to the cave, trampling or grazing my horses fording the Rio Grande from Mexico, and the transitory nature of the site itself, with blowing and rain scattered sand moving over and around plants. At the flat site, the movement of sand is the main threat.
Bonamia ovalifolia has no legal protection under the Endangered Species Act, although globally it is considered to be in danger of extinction.
Desert Botanical Garden has small, inadequate collections from both populations. Garden staff visits west Texas 2 to 4 times annually, and has been fortunate enough to be able to collect seeds from Bonamia from three good years (years having adequate rainfall to allow flowers to form). We currently have 953 seeds from the larger population, and 103 seeds from the other site. A germination test conducted in 1993 produced 6 plants, which finally produced a single flower in 1994. In the fall of 1994, plants went dormant, but never emerged with new growth in the spring. The Garden has formed a cooperative agreement with Dr. Bonnie Amos of San Angelo University, San Angelo, Texas to investigate germination requirements for this species. Dr. Amos and a graduate student gathered a sufficient number of seeds during 1998 to conduct germination tests. With Dr. Amos, the Garden has developed a germination experiment protocol, and will soon begin the experiment. The results will be communicated upon completion of the tests. Plants grown from these seeds could be used for reintroduction, under a carefully planned regimen developed in conjunction with personnel from Big Bend National Park. Other plants could be used to study reproductive biology of Bonamia in greater detail.
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