Natural Variation in \u3cem\u3eAbies\u3c/em\u3e of the Southern Appalachians

Determinations were made of several foliage, seed, and cone characteristics from material collected throughout the ranges of Abies fraseri in high elevations of Tennessee, North Carolina, and southern Virginia; Abies balsamea var phanerolepis in West Virginia and northern Virginia; and Abies balsamea from its southernmost distribution in Pennsylvania and southern New York. Natural variation was investigated to determine relationships among these taxa, especially with reference to possible hybridity of A. balsamea var phanerolepis in West Virginia and northern Virginia. Much variation was found among species groups among stands within groups. Variation patterns suggested sampling from a north-south cline. Stand values of many characteristics overlapped, in many cases obscuring taxonomic boundaries. High correlation with north-south geographic location was shown for many characteristics. Variation was no greater within the intermediate fir stands (A. balsamea var phanerolepis) than within Fraser fir stands for 12 of the 13 characteristics analyzed, and distribution of hybrid index values of the intermediate fir was normal. The theory of hybrid origin of intermediate fir in West Virginia and Virginia was not generally upheld. Only one characteristic, leaf scar width showed wider variation within the intermediate stands than within Fraser or balsam fir. Total hypodermal cells discriminated well between Fraser fir and the other firs, but not between balsam fir and intermediate fir. The traditional cone bract length-scale length ratio was the only characteristic which distinguished absolutely among the three taxa with no overlapping of values. The ratio is calculated from bract length and scale length which very more or less inversely to each other from north to south. The ratio exaggerated differences due to variation of either characteristic. Differences among Abies fraseri, A. balsamea, and A. balsamea var phanerolepis may be less distinct than heretofore believed