Evaluation of suitable habitat for reintroduction of the endangered species Abronia macrocarpa as a recovery measure

Background/Question/Methods

Reintroduction is emerging in conservation biology as a viable method for recovering endangered species. A major element for successful reintroduction is identification of suitable habitat. Approaching reintroduction from an ecosystem perspective, factors to consider in identification of suitable habitat to support endangered plant species include edaphic features and community composition. We tested potential of reintroduction as a recovery method using Abronia macrocarpa, an endangered species endemic to Texas. The plant grows in deep sandy soils in open areas of the Post Oak Savannah Woodlands. The plant has a USFWS recovery priority of 2 indicating a high degree of threat, but high recovery potential. Recovery criteria set forth are to develop and implement management plans that insure continued protection of at least 20 viable populations, each at least 25 acres in size with a stable population of at least 600 plants. Currently, nine populations are known. Reintroduction will become critical to recovery of this endangered species in the event that an additional 11 populations do not exist in the wild. The study objective was to determine habitat characteristics necessary for successful reintroduction. We characterized edaphic features, community composition, and community similarity of seven sites supporting naturally occurring populations of A. macrocarpa.

Results/Conclusions

Soil pH range was 5.3 to 6.6. Coefficient of community index values ranged from 0.67 to 0.99. Principal component analysis showed a strong correlation in the presence of Rhododon ciliatus, Plantago sp. and Croton argyranthemus. We used these data to select three experimental sites to test reintroduction via seed. Soil pH of the three sites ranged from 5.5 to 5.6. Community similarity index values of the three sites compared to sites supporting Abronia populations ranged from 0.43 to 0.85. Mean percentage seed germination was 16.33% at site 1, 16.67% at site 2 and 4.2% at site 3. Germination was significantly higher at sites 1 and 2 when compared to site 3 (p-value = 0.01303, F = 5.88, df = 2). The three sites shared at least 50% of the same species as the A. macrocarpa seed source community. Plantago sp. and C. argyranthemus occurred at all three sites. However, Rhododon ciliatus was present at sites 1 and 2, but not at site 3. Results suggest R. ciliatus may be an important indicator for selecting suitable habitat for reintroduction of A. macrocarpa.