Journal Article

Population genetic structure of two <i>Medicago</i> species shaped by distinct life form, mating system and seed dispersal

Juan Yan, Hai-Jia Chu, Heng-Chang Wang, Jian-Qiang Li and Tao Sang

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 103, issue 6, pages 825-834
Published in print April 2009 | ISSN: 0305-7364
Published online January 2009 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcp006
Population genetic structure of two Medicago species shaped by distinct life form, mating system and seed dispersal

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Life form, mating system and seed dispersal are important adaptive traits of plants. In the first effort to characterize in detail the population genetic structure and dynamics of wild Medicago species in China, a population genetic study of two closely related Medicago species, M. lupulina and M. ruthenica, that are distinct in these traits, are reported. These species are valuable germplasm resources for the improvement of Medicago forage crops but are under threat of habitat destruction.

Methods

Three hundred and twenty-eight individuals from 16 populations of the annual species, M. lupulina, and 447 individuals from 15 populations of the perennial species, M. ruthenica, were studied using 15 and 17 microsatellite loci, respectively. Conventional and Bayesian-clustering analyses were utilized to estimate population genetic structure, mating system and gene flow.

Key Results

Genetic diversity of M. lupulina (mean HE = 0·246) was lower than that of M. ruthenica (mean HE = 0·677). Populations of M. lupulina were more highly differentiated (FST = 0·535) than those of M. ruthenica (FST = 0·130). For M. lupulina, 55·5 % of the genetic variation was partitioned among populations, whereas 76·6 % of the variation existed within populations of M. ruthenica. Based on the genetic data, the selfing rates of M. lupulina and M. ruthenica were estimated at 95·8 % and 29·5 %, respectively. The genetic differentiation among populations of both species was positively correlated with geographical distance.

Conclusions

The mating system differentiation estimated from the genetic data is consistent with floral morphology and observed pollinator visitation. There was a much higher historical gene flow in M. ruthenica than in M. lupulina, despite more effective seed dispersal mechanisms in M. lupulina. The population genetic structure and geographical distribution of the two Medicago species have been shaped by life form, mating systems and seed dispersal mechanisms.

Keywords: Medicago lupulina; Medicago ruthenica; microsatellite; genetic diversity; gene flow; forage legume

Journal Article.  6119 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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