Abstract
SummaryAll 12 of the taxa in Sedum section Gormania are geographically restricted to western North America, occurring on a variety of rock outcrops that range in elevation from 55 to nearly 3700 meters. Evolutionary divergence of the taxa has been facilitated by temporal isolation of the flowering periods, cytological differentiation, and changes in the breeding systems. Species adaptation and restriction to particular substrates that are isolated in the geologically diverse Klamath region appear to have fostered narrow endemism of some of the taxa. Four of the taxa are putative relicts and are characterized as diploids, morphologically homogeneous, highly self‐compatible, and narrowly restricted at low elevations to a single type of substrate. Vegetative reproduction in the relictual taxa is much less than that in related taxa. Those taxa that appear to be more recently evolved have at least two of the following features: tetraploidy or hexaploidy, morphological heterogeneity, extensive vegetative reproduction, low level of self‐compatibility, occurrence on geologically recent substrates, or a wide distribution.
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