Origin of Symphyotrichum anticostense (Asteraceae, Astereae), an endemic, high polyploid species of the Gulf of St. Lawrence region, based on morphological and nrDNA evidence

Abstract

Symphyotrichum anticostense (Fernald) G.L.Nesom (Asteraceae, Astereae), a rare endemic of the Gulf of St. Lawrence region, is a high allopolyploid (2n = 10x = 80). It has been hypothesized to be derived from the hybrid between tetraploid (2n = 4x = 32) individuals of Symphyotrichum boreale (Torr. & A.Gray) Á.Löve & D.Löve and the hexaploid (2n = 6x = 48) Symphyotrichum novi-belgii (L.) G.L.Nesom. We investigated this hypothesis using morphological and molecular internal transcribed spacer sequence data, and we tried to determine the potentially geographic origins of the taxon. Univariate morphological analyses show that 67.5% of the S. anticostense characters are parent-like, 43.5% from S. novi-belgii and 13% from S. boreale, the remainder not differing statistically from either parent; 23.5% are intermediate and 9% transgressive. Multivariate analyses show that S. anticostense is intermediate between its putative parents. The molecular results support the morphological data, but due to the insufficient resolution among ribotypes on the tree, a more rapidly evolving marker will be needed to more reliably ascertain the origin of S. anticostense. Besides the hypothesis of genetic drift and allele fixation following long-distance dispersals, at least three independent geographic origins may be suggested for S. anticostense; Anticosti Island, Lake St. John, and Gaspé Peninsula-New Brunswick-Maine.