| Summary: | Layering, a form of clonal propagation, has been documented to occur in
Chamaecyperis nootkatensis (D. Don) Spach (Cupressaceae), but little is known about the
frequency and spatial extent of this phenomenon. Clonal reproduction has the potential to
greatly affect population genetics parameters such as fine scale genetic variation and genetic
structure, and, ultimately, how populations evolve. C. nootkatensis is an economically important
coniferous tree species in the forests of the Pacific Northwest. Five microsatellite loci were
developed from an enriched genomic library of C. nootkatensis. The developed microsatellite
loci showed significant inbreeding in the three natural populations of C. nootkatensis surveyed.
A segregation analysis and a test for deviations from Hardy Weinberg equilibrium revealed that
one of the five loci was affected by null alleles in high frequency. Interspecific amplifications
showed support for a close relationship of C. nootkatensis with members of the genera
Cupressus and Juniperus. These microsatellite markers were utilized to infer the frequency and
spatial extent of clonally derived individuals in three natural populations of C. nootkatensis and
investigate the potential effects of clonal reproduction on fine scale genetic diversity and genetic
structure in this species. Clonal extent was found to vary greatly between populations and no
clear relationship between clonal extent and specific habitats was detected. Clonal diversity
showed that on average -23% of the trees sampled were clonally derived. Fine scale genetic
structure, as detected by genetic spatial autocorrelation, and the coefficient of inbreeding
increased with clonal extent. The greatest effect of clonality on fine scale genetic structure was
detected between trees separated by approximately five meters or less (the average size of
clonal patches). Surprisingly, no relationship was observed between clonal extent and genetic
variation. Clonality may play a crucial role by propagating this species, when the effect of
purging genetic load in the inbred C. nootkatensis results in extremely low sexual recruitment.
Clonality may also be conserving very fit gene combinations from recombination.
Key Words: Chamaecyparis nootkatensis, clonality, Cupressaceae, genetic diversity, genetic
structure, microsatellite, population genetics, simple sequence repeat (SSR), yellow cedar.
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