Population biology of Sedum integrifolium ssp. leedyi

Conservation biologists use information about the reproduction, life history, and genetic distinctness and variability of plant taxa to set conservation priorities and to design management strategies. I investigated rates of flowering, seed set, germination, and clonal reproduction in populations of the federally and state listed Sedum integrifolium ssp. leedyi and estimated the taxon's levels of distinctness and variability. The study included plants from four of the five known S. integrifolium ssp. leedyi populations and 11 populations of the three more common S. integrifolium subspecies. Plants from S. rosea and S. rhodanthum populations provided comparisons of levels of distinctness within S. integrifolium with levels of distinctness among the species. Flowering and germination rates differed significantly among the S. integrifolium ssp leedyi populations (P {dollar}<{dollar} 0.001) and suggest that the single formally protected population may be experiencing inbreeding depression or environmental stresses. Seed set rates did not significantly differ among the populations (P = 0.137). The average germination and 6-month survival rates (77 and 98% respectively), suggest that cultivation from seed will be a viable means of ex situ propagation. Plants flowered 4-6 months after germination and produced mature fruits 1-2 months later, suggesting that they may reproduce sexually in their first or second season of growth. I assayed 26 plant clusters (81 stems) using 28 randomly amplified polymorphic DNA (RAPD) markers for evidence of clonal reproduction. Of the 81 stems, 75 had differing genotypes and only three pairs had identical genotypes, suggesting that clonal reproduction is infrequent. Estimations of genetic distinctness and variability were made using 34 RAPD markers (258 plants) and 37 morphological characters from plants (1320) grown in a common garden. The data show that each S. integrifolium ssp. leedyi population is highly distinct from the other S. integrifolium subspecies and from one another. I conclude that S. integrifolium ssp. leedyi merits protection under the Endangered Species Act and that each S. integrifolium ssp. leedyi population should be managed as a distinct evolutionary unit.