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Echinocereus chisoensis (Chisos Mountain Hedgehog cactus) was listed threatened under the Endangered Species Act on September 30, 1988. Big Bend National Park has actively worked to conserve the species since 1982, when the species was included in the Natural Resources Management Plan. Permanent monitoring plots were established and plants that were salvaged from road work were sent to the Chihuahuan Desert Research Institute and Desert Botanical Garden.
Plants are truly rare, occurring in small numbers across the range, which consists of several sites within Big Bend National Park on flat desert pavement in a Larrea tridentata/Opuntia schottii community type. Plants are found growing at the bases of creosote bushes, and also among the stems of dog cholla. Distribution is widely scattered. The major threat to these cacti is collection, environmental stress and lack of reproductive fitness.
The plants can be single or multiple-stemmed, are up to 9 inches high, with rows of grayish spines. They produce flowers that are incredibly spectacular in tri-colored shades of pink, between April and July. A light fragrance is emitted during morning and evening. The fruits are semi-dry, splitting open along the side when mature, producing hundreds of seeds.
During 1999, Dr. Bonnie Amos, from San Angelo State University, and Chris Vassilou conducted reproductive biology studies on Echinocereus chisoensis at four sites in Big Bend National Park. They applied four treatments at each site: open-pollination, self-pollination (exclosing flowers before and after selfing), cross-pollination with pollen collected from nearby plants, and exclosed with no manipulation.
Fruit set was high on open-pollinated plants, demonstrating that pollinator activity is adequate. Cross-pollinated flowers yielded similar results as open-pollinated flowers.
The exclosed and selfed plants produced very few fruits, leading to the conclusion that Echinocereus chisoensis is probably self-incompatible.
Fruits produced as a result of these studies were sent to Desert Botanical Garden where seeds were hand-cleaned and counted to determine number of seeds per fruit for each treatment at each site. Numbers of seeds per fruit vary considerably with numbers ranging from 200 to over 700. The seed viabilities and germination percentages are now being tested at Desert Botanical Garden.
A portion of the seeds will be used to produce plants that can be used for a seed and seedling ecology experiment, essentially involving an attempt at augmentation of the populations at the four sites. Seedlings will be planted at the bases of creosote bushes and monitored for survival over time.
In addition to traditional studies, we would also like to explore a hydration-rehydration technique of seed germination developed by Joseph Dubrovsky (1996). Dubrovsky allowed seeds of three species of cacti, Stenocereus thurberi, Ferocactus peninsulae and Pachycereus pecten-aboriginum, to imbibe, then dehydrate, then re-imbibe. The treated seeds germinated faster than untreated seeds, a strategy for survival allowing seedlings to accumulate a greater biomass during optimal conditions for germination and initial growth.
Desert Botanical Garden has an ongoing agreement with the US Fish and Wildlife Service to establish a conservation seedbank of thirteen rare plants that grow in west Texas, including Echinocereus chisoensis. Under this agreement, some of the seeds sent to Desert Botanical Garden will be seedbanked both at the Garden and at National Seed Storage Lab. The remainder will be returned to Big Bend National Park, and distributed near the plants they came from. Dr. Amos will then attempt to track the success rates of seedling establishment in different microhabitats over time. We feel that the apparently low reproductivity of this species may be linked directly to seed ecology.
Dubrovsky, J. 1996. Seed hydration memory in Sonoran Desert Cacti and its ecological implication. Journal of Botany 83(5): 624-632.
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