A Study of Wild Leek, and the Recognition of Allium burdickii (Liliaceae)

Abstract

The combination of reproductive isolation and significant morpholog- ical differences supports the recognition of two species of wild leek: Allium tricoccum Solander in Aiton and A. burdickii based on A. tricoccum var. burdickii Hanes. Plants of the latter are considerably smaller and have fewer flowers per umbel than those of the former. They also consistently lack the red pigmentation usually evident in scapes and petioles of A. tricoccum. Although the two taxa often occur together, hybridization between them is precluded by a phenological barrier. In 1977 and 1978, Illinois populations of A. burdickii flowered from June 2-21, while those of A. tricoccum began flowering about July 1. An estimated frequency of occurrence based on herbarium collections indicates that the probable center of distribution for A. burdickia lies in the area bounded by northern Illinois, northern Indiana, southern Wisconsin and southern Michigan. In the eastern United States, A. tricoccum seems to be the more common of the two species. As no type specimen of A. tricoccum can be found, a neotype is designated. Allium tricoccum Solander in Aiton (1789) is the eastern North Amer- ican counterpart of the Old World ramson or bear leek, A. ursinum Lin- naeus. Known in the Midwest as wild leek and in the Appalachian Moun- tains as ramps, the species is a forest floor component of the northern hardwood association. The plants do not occur west of the 100th merid- ian. In the Great Lakes area and northeastward, they grow on streamside bluffs, in depressions, and in maple-dominated upland woods. In the southern extension of range, the plants are confined to colluvial moun- tain slopes at increased elevations (between 1000 and 3000 m), probably as a response to the higher prevailing temperatures. The existence of two well-defined morphological variants of wild leek was first reported by Hanes and Ownbey (1946) who studied populations in the woodlands of Prairie Ronde Township, Kalamazoo County, Mich- igan. They published and elaborated short descriptions taken from a letter by J. H. Burdick to Asa Gray which had accompanied specimens collected in 1877 in Milton, Wisconsin. Gray, and subsequently Fernald, considered the variations a response to environmental factors and, re- portedly with some reluctance, Hanes and Ownbey adopted the concept of ecological races for the two taxa. In addition to the morphological distinction based primarily on differences in size and type of pigmen- tation, the authors also noted differences in the floral development of the two taxa. In 1953 Hanes published the name Allium tricoccum var. burdickii in honor of the man who first noticed and collected this variant. No type or authentic specimen could be found for Allium tricoccum.