Meriem Laouar

• Biodiversity Journal, 5 (4): 481–498

  Meriem Laouar & Aïssa Abdelguerfi
  Little effect of ecological factors and symbiotic specificity on the distribution of Medicago subsect. Intertextae (Urban) Heyn in the Mediterranean Basin

  ABSTRACT
  In the Mediterranean region, Medicago granadensis Willd. and M. muricoleptis Tineo (Fabales Fabaceae) of the Intertextae subsection are rare and present, each one in well defined areas, whereas the others taxa, in the same subsection, M. ciliaris (L.) All. and M. intertexta (L.) Mill., are more frequent with large distribution. This kind of geographical distribution is not a coincidence; certainly different factors are the origin of this distribution. In 125 sites of different Mediterranean countries, the ecology of the four taxa was studied, 34 trapped strains in one site of Intertextae rhizobiums were characterized by rep-PCR and some symbiotic tests were carried out. The results confirm that M. muricoleptis and M. granadensis are endemic in the north and east of the Mediterranean, respectively; whereas, M. ciliaris and M. intertexta are widespread. Although their geographic specificity, the four taxa showed no important differences in ecological conditions. M. muricoleptis, given its presence in the north of the Mediterranean only, is distinguished by its precipitation requirement. By inference, the absence of M. muricoleptis and M. granadensis in some regions is not due to the absence of the symbiont. We confirm the symbiotic specificity of Sinorhizobium medicae (Rome, 1996) for the Intertextae subsection and the existence of coevolution between taxa (widespread and endemic) and rhizobia. We suppose that endemic taxa are in the process of allopatric speciation, which explains their narrow distribution in the Mediterranean Basin.

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