Ecotypes or Genotypes? The Status of the Currently Recognized Infraspecific Taxa of Acacia tortilis (Forssk.) : Hayne Growing in the Red Sea Hills, Sudan and Egypt
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This study focuses on the Acacia tortilis species complex and the taxonomic relationship among its currently recognized infraspecific (A. tortilis ssp. tortilis, ssp raddiana and ssp. spirocarpa) in the Red Sea Hills of North-East Sudan and South-East Egypt. The morphological features used in floras to differentiate among these taxa were examined on a total of 520 specimens, collected from 33 localities. It was found that there is an association between the morphological characters and their immediate environment. Of 158 specimens subjected to molecular analysis 106 showed no agreement between classes formed using morphological and / or molecular data. In spite of the great genetic polymorphism among all the 158 specimens, there was no significant difference among the three putative A. tortilis sub-taxa. Genetic diversity among the samples studied seems linked to restricted gene flow among populations, but a positive correlation was found between the genetic variation and the physical distance between A. tortilis localities studied. Discriminating morphological characters of A. tortilis such as crown shape and growth form seem to be a result of traditional human management activities such as animal browsing and pollarding at different life stages. The currently recognized infraspecific taxa of Acacia tortilis in the Red Sea Hills, Sudan and Egypt appear to be ecotypes rather than genotypes, and accordingly the A. tortilis complex in the Red Sea Hills of Sudan and Egypt comprises only one species i.e. A. tortilis.