Population genetic structure of the Gulf of St. Lawrence aster, Symphyotrichum laurentianum (Asteraceae), a threatened coastal endemic

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Abstract:

The Gulf of St. Lawrence aster (Symphyotrichum laurentianum (Fernald) G.L.Nesom) is an endemic annual of saline habitats in the southern Gulf of St. Lawrence. It is listed as a threatened species, and has recently experienced population declines in much of its range. We used 11 allozyme markers to assay population genetic variation in six wild populations of S.laurentianum from the Magdalen Islands, Quebec (QC), the only remaining wild population from Prince Edward Island National Park (PEI), and a greenhouse population founded in 1999 with seed collected from PEI. Symphyotrichum laurentianum harbours moderate genetic diversity (Ps = 0.36, As = 1.54), with only modest spatial genetic structure (pairwise FST< 0.15) and no significant isolation by distance. The PEI population had greatly reduced allelic diversity compared with the populations from the Magdalen Islands, which likely act as a reservoir of genetic variation in S.laurentianum. Recent loss of alleles during population decline in PEI is suggested by the retention of greater allelic diversity in the greenhouse population. Estimates of breeding structure suggest small but nonzero rates of outcross pollination (FIS = 0.73, 95% CI = 0.48–0.97; outcrossing rate ~16%). Population genetic structure in S.laurentianum can inform those forming and carrying out conservation and recovery plans for this threatened species.

L'aster du Golfe St-Laurent (Symphyotrichum laurentianum (Fernald) G.L.Nesom) est une endémique annuelle d'habitats salins, dans le sud du Golfe St-Laurent. On la retrouve sur la liste des espèces menacées, et l'on observe récemment un déclin de ses populations dans plusieurs régions de son aire de distribution. Les auteurs ont utilisé 11 marqueurs allozymiques pour évaluer la variation génétique des populations dans six populations indigènes du S. laurentianum provenant des Iles de la Madeleine (QC), de la seule population indigène résiduelle du Parc National de l'Île du Prince-Édouard (PEI) ainsi que d'une population établie en serre en 1999, à partir de semences venant de PEI. Le S. laurentianum présente une variation génétique modérée (Ps = 0,36; As = 1,54), avec seulement une modeste structure génétique spatiale (Fst < 0,15 par paire) et aucun isolement significatif par la distance. La population de PEI montre une diversité allélique plus réduite comparativement à celles des Îles de la Madeleine, qui agissent vraisemblablement comme réservoir de variation génétique pour le S. laurentianum. La conservation d'une plus grande diversité allélique dans la population maintenue en serre suggère une perte récente d'allèles au cours du déclin de la population de PEI. Une estimation des structures de fécondation suggère des taux de pollinisation croisée faibles mais supérieurs zéro (Fis= 0,73; 95% CI = 0,48–0,97; taux de croisement ~16%). La compréhension de la structure génétique des populations du S. laurentianum peut servir de base pour la conservation et la réhabilitation de cette espèce menacée.

Document Type: Research Article

Publication date: November 1, 2009

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  • Published since 1929, this monthly journal features comprehensive research articles and notes in all segments of plant sciences, including cell and molecular biology, ecology, mycology and plant-microbe interactions, phycology, physiology and biochemistry, structure and development, genetics, systematics, and phytogeography. It also publishes commentary and review articles on topics of current interest, contributed by internationally recognized scientists.

    Previously published as the Canadian Journal of Botany
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