Variation in Erigeron philadelphicus (Compositae)

Abstract

Plants of Erigeron philadelphicus L. var. glabra Henry, E. philadelphicus forma angustatus Marie-Victorin & Rousseau, and E. provancheri Marie-Victorin & Rousseau were grown in cultivation, where all retained their characters and had a diploid chromosome number of 2n = 18. Variety glabra was found to be an ecotype of E. philadelphicus which is only known from salt marshes at Port Albemi, Vancouver Island, B.C. It is distinguished by its subglabrous stem, leaves, and involucres and its somewhat fleshy leaves. Erigeron provancheri and E. philadelphicus f. angustatus are very similar to each other in morphology. They represent different populations of a single taxon, E. philadelphicus ssp. provancheri (Marie-Victorin & Rousseau) J. K. Morton stat.nov. It is distinguished by its perennial subglabrous habit, small size, small capitula, and white or nearly white ligulate florets. Only four populations are known: a population from the tidal estuary of the St. Lawrence near Quebec City; one in a similar habitat on the Hudson River near New York; one on the Waits River in Bradford, VT; and one on dolomite rocks along the shores of Lake Huron at the tip of the Bruce Peninsula and on nearby islands.