PARENT SESSION
Oral Session #92: Conservation Ecology: Genetics, population viability, interactions.
Presiding: W. Wirtz
Thursday, August 8. 1:00 PM to 3:45 PM. Grand Ballroom West, Radisson.

Morphological, phenological, and genetic characterization of an endangered plant and its hybrid swarm: Protection implications.

Maschinski, Joyce^*,1, Baggs, Joanne^1,2, Travis, Steven³, ¹ The Arboretum at Flagstaff, Flagstaff, AZ² USDA USFS Humboldt-Toiyabe National Forest, Sparks, NV³ USGS National Wetlands Research Center, Lafayette, LA

ABSTRACT- Depending upon circumstance, hybridization has been regarded as either a threat or an aid to the conservation of rare species. In Verde Valley, Arizona, the range of the endangered Purshia subintegra overlaps with the more common cliffrose, Purshia stansburiana and introgression occurs. We conducted common garden, phenological, and genetic studies to examine the Verde Valley population of the endangered species in relation to the common species and introgressed forms. In a greenhouse, we examined morphological characters of plants established in soils from parental and hybrid habitats. The two parental species and introgressed forms maintained detectable morphological differences for 80 weeks regardless of soil type. Discriminant function analysis indicated that individuals were successfully classified, although introgressed forms showed more phenotypic variability than parents. In the wild, parental species and introgressed forms have distinct differences in flowering time. Introgressed forms had two bouts of flowering, which overlap with parental species. In addition, habitat distributions of P. subintegra, P. stansburiana, and introgressed forms are significantly different. Genetic analysis (AFLP) indicated that P. subintegra forms a large hybrid swarm with P. stansburiana in the Verde Valley. The two parental species are not well differentiated with neutral markers. Discriminant function analysis indicated that introgressed forms are a fairly cohensive array of complex backcrosses, not simple F₁ hybrids. The maintenance of morphological differences despite the gene flow suggests strong selection is maintaining morphological and phenological characters of the parental species and introgressed forms in the Verde Valley. However, with habitat destruction that will likely favor introgressed forms, the persistence of P. subintegra in the Verde Valley is threatened.

KEY WORDS: endangered species, genetics, introgression, niche partitioning