ISOENZIMATIC STUDIES IN SOUTH AND NORTH-AMERICAN SPECIES OF SECTION ALGAROBIA, GENUS PROSOPlS (LEGUMINOSAE).

SAIDMAN B. O.; MONTOYA S.; BESSEGA C.; JULIO N; FERREYRA L. I.; VILARDI J. C.

San Antonio, Texas

Congreso; 9th International Congress on Genes, Gene Families and Isozymes.; 1997

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The section Algarobia includes promising multipurpose tree and shrub species in arid and semiarid regions. In its main diversity center (Chaco Biogeographic Region, South America) a group of sympatric hybridizing species constitutes a syngameon. In the present work 37 populations representing two natural hybrids, 10 south american, P. caldenia, P. flexuosa P. alba, P. hassleri, P. chilensis, P. alpataco, P. nigra, P. ruscifolia, P. vinalillo P. juliflora (4x), and two north american species, P. glandulosa, P. velutina, were analyzed isoenzymatically, with the aim of determining the relationships among thern, the internal structure of the syngameon, the applicability of biological species concapts to this complex, and the significance of hybridlization in its evolution. Hybrid populations were not isoenzymatically intermediate between their putative parents. Genetic identities were very high even between species of different subcontinents (ex gr. P. glandulosa- Texas and P. ruscifolia- Argentina-: l= 0.9) and variabilities (H= 0.2-0.3) did not differ significantly among species. However, gene flow estimates and identities are higher within (Nm >2) than between species (Nm <1). The results suggest that: the high similarities between species are not the result of hybridization. P. glandulosa would have originated recently from south American relatives. Specific integrity is preserved in the syngameon by cohesive mechanisms related to ecological or selective constraints. Hybridization in this group would not be an homogenizing mechanism but might play a major role in speciation.