Rhodiola integrifolia ssp. leedyi (Rosendahl & Moore) Kartesz
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Sedum rosea var. integrifolium, Sedum integrifolium ssp. leedyi, Sedum rosea var. leedyi
Basis for Listing
Rhodiola integrifolia ssp. leedyi is an isolated subspecies of a common western species that ranges from Alaska to California. There are three western subspecies, but none have a geographic range that reaches Minnesota or overlaps with that of ssp. leedyi. This subspecies was discovered by John Leedy in 1936 on a cliff along the North Branch Root River near Simpson, Minnesota in Olmsted County (Rosendahl and Moore 1947). Before then, it was unknown to science. Molecular and morphological studies show that this subspecies is very distinct from the other subspecies (Olfelt et al. 2001). There are a total of seven known populations of ssp. leedyi; four in Minnesota and three in New York (U. S. Fish and Wildlife Service 1998). Current population estimates for the Minnesota populations range from about 175 plants at the smallest site to about 1,020 plants at the largest (Olfelt 2003). Because of the exhaustive field searches that have already been conducted, it is doubtful that additional populations will be found.
Rhodiola integrifolia ssp. leedyi is a very distinctive plant that cannot be easily mistaken for any other native Minnesota species. The stems and leaves are smooth and succulent, and the leaf margins are irregularly dentate to entire. The thick, scaly rhizomes are prominent in the narrow rock crevices where the plants are rooted. It is dioecious, meaning the male flowers and female flowers are on separate plants. The flowers are red or yellow and occur in flat-topped clusters (cymes) (Clausen 1975).
The New York populations of R. integrifolia ssp. leedyi occur on cliffs along the western shore of a lake. In Minnesota, this species is found on shallow ledges on north-facing dolomite cliffs about 30 m (98 ft.) in height. Plants are restricted to crevices in maderate cliffs, a very specialized habitat of specific strata where groundwater seeps through the rock and is cooled by air coming from underground air passages in karst topography. This results in a constantly wet, dripping condition, an unusual product of a long geological history.
Biology / Life History
Reproduction in R. integrifolia ssp. leedyi occurs both sexually by seed and vegetatively by fragmentation of rhizomes. Flowers are insect-pollinated. Seeds at one New York site are reported to sometimes germinate in their follicles and produce seedlings on the parent plant (Clausen 1975). There is evidence from cultivation trials that plants may become sexually mature in their first or second season of growth and that clonal reproduction may be infrequent (Olfelt 1998).
Conservation / Management
The strategy for the conservation of R. integrifolia ssp. leedyi should involve a variety of actions, including fee acquisition of habitat. There is probably little that can be done to directly enhance protection of cliff-faces themselves, other than to prohibit rock climbing. But it is important to ensure that management practices on adjoining lands do not have an adverse effect on this species. Field and greenhouse studies suggest that the population on the only publicly owned site in Minnesota might be experiencing inbreeding depression or environmental stress. The two populations on privately owned land appear to be relatively stable (Olfelt et al. 1998). Because individual populations are as genetically distinct from each other as the subspecies is from its western relatives, a redundant, formal protection strategy for R. integrifolia ssp. leedyi is appropriate.
Conservation Efforts in Minnesota
Biological understanding of this species exceeds conservation efforts. A publication entitled, Leedy's roseroot: a cliffside glacial relict (Sather 1993) was produced for the U.S. Fish and Wildlife Service and is available to the public. Also, a federal recovery plan was prepared that presents detailed actions necessary to secure the recovery of this species (U.S. Fish and Wildlife Service 1998). From 1997 to the present, the number of R. integrifoliassp. leedyi individuals has been annually counted in most of the Minnesota populations. Sound estimates of population sizes and demographic characteristics are critical to developing intelligent management strategies for this species and should continue. This information enables us to predict the long-term viability of Minnesota populations.