The importance of competition in the isolation and establishment of Helianthus paradoxus (Asteraceae)

Abstract

Helianthus paradoxus (the Pecos or puzzle sunflower) is a threatened, federally listed annual species that is found in a few locations in west Texas and New Mexico. Two greenhouse experiments were conducted to evaluate the ability of H. paradoxus to compete with its progenitors and a with potential ecosystem competitor, Distichlis spicata (saltgrass) in simulated salt marsh and non-salt marsh environments. The results were usually dependent on soil salinity. Helianthus paradoxus was the better competitor in high saline soil and its progenitor H. annuus (common sunflower) was the better competitor in low saline soil. However, H. paradoxus was the better competitor in both high and low saline soils when compared to it progenitor H. petiolaris (plains sunflower) and to D. spicata, an ecosystem competitor. The ability of H. paradoxus to tolerate higher saline conditions, and perhaps even restrict the more geographically widespread H. annuus in saline soils may have allowed H. paradoxus to establish, become genetically isolated and survive as a species in inland salt marshes. Data presented here indicate that while H. paradoxus can grow in low saline soil, interference from H. annuus in low saline soils could restrict H. paradoxus to saline environments within salt marshes. The ability of H. paradoxus to out-compete D. spicata at high or low salt levels indicates that gaps in D. spicata vegetation would not be necessary in the salt marsh to allow the establishment and persistence of H. paradoxus in the saline soils of the salt marsh environment.

Parent Publication

• Southwestern rare and endangered plants: Proceedings of the Fourth Conference

Citation

Van Auken, Oscar W.; Bush, Janis. K. 2007. The importance of competition in the isolation and establishment of Helianthus paradoxus (Asteraceae). In: Barlow-Irick, P.; Anderson, J.; McDonald, C., tech eds. Southwestern rare and endangered plants: Proceedings of the Fourth Conference; March 22-26, 2004; Las Cruces, New Mexico. Proceedings. RMRS-P-48CD. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 122-135