Stability of nuclear DNA content among divergent and isolated populations of Fraser fir

Fraser fir (Abies fraseri (Pursh) Poir.) is an endemic species consisting of six major disjunct populations in the Appalachian Mountains, U.S.A. Nuclear DNA content was measured with laser flow cytometry to determine if genome size differences could be detected among the disjunct populations of Fraser fir and its close relatives, balsam fir (Abies balsamea (L.) Mill.) and Canaan fir (A. balsamea var. phanerolepsis Fern.). The mean DNA content for Fraser fir was 17.2 pg/C, which was similar to the two related fir species. There were no significant differences among disjunct Fraser-fir populations. Mean DNA content differences for fir species in the southern Appalachian Mountains were similar even with speciation events (7000 B.P.) and subsequent population isolation. In the absence of polyploidy or large chromosomal rearrangements, genome size changes in conifers occur on a broad evolutionary time scale.Key words: conifers, gymnosperm, C-values, nuclear genome, Abies fraseri.