Morphology, geography, and ecology of incised-leaf variants of Symphyotrichum lowrieanum (Asteraceae)

Abstract

Specimens identified as Symphyotrichum cordifolium and S. lowrieanum with incised and pinnatifid leaves have been noted since the mid-1800s. A search of herbarium records uncovered 31 unique collections and 53 herbarium sheets of plants whose leaf incisions and lobes ranged from 4–18 mm in length. In most specimens, at least half the cauline leaves had incised leaves. Basal leaves tended to be cordate, truncate, or rounded at the base and long rhizomes were often associated with the incised-leaf form. Incised-leaved specimens occurred in eight states, ranging from Maine to Tennessee, with concentrations in Pennsylvania and Tennessee. Most collection sites were associated with shale or limestone/dolomite in the Ridge and Valley and Appalachian Plateaus physiographic provinces at elevations of 200–800 m. Repeat collections of incised-leaved specimens from several populations showed spatial and temporal persistence of the variant phenotype. Although variants comprised the majority form in some populations, typical S. lowrieanum was usually also present. Circumstantial evidence suggested the incised-leaf phenotype has a genetic basis. The geographic, ecological, and temporal associations are best acknowledged by use of the rank of variety as; Symphyotrichum lowrieanum (L.) G.L. Nesom var. incisum (Porter ex Britton) F. Levy, comb. nov.