NATURAL HYBRIDIZATION BETWEEN BLACK SPRUCE AND RED SPRUCE

Using species-specific random amplified polymorphic DNA (RAPD) markers and morphological characters, natural hybridization between the close ly related black spruce Picea mariana (Mill.) B.S.P. and red spruce P. rubens Sarg. was evaluated in natural populations from north-eastern North America. Sampling included populations from both areas of allopa try and also 14 populations from part of the area of sympatry located in the province of Quebec and covering several thousands of square kil ometres. Classification results from RAPD species-specific markers and from a discriminant function based on morphology were compared. Molec ular analysis of the allopatric populations indicated a small amount o f interspecific gene leakage with no asymmetric directionality to intr ogression. A high occurrence of hybrid/introgressant individuals was o bserved within sympatric populations, suggesting weak reproductive iso lation. As expected, the detection of such individuals was more effici ent using molecular markers than with morphological traits. The hybrid zone appeared extensive with variable species structure and, in some stands, the main component composed of hybrid/introgressant trees. Imp lications for the genecology and genetic management of these species a re discussed.