Identification of Prosopis juliflora and Prosopis - Universidad Pública ...

2species are sympatric in each centre. Studies using morphological characters(Solbrig et al. 1977), isoenzymes (Saidman 1985), seed protein electrophoresis(Burghardt and Palacios 1997) and molecular markers (Ramírez et al. 1999)have shown the occurrence of intra- as well as inter-series hybrids in populationsof both sections Algarobia and Strombocarpa. These studies, however,support the division of the genus into sections. Pasiecznik et al. (2001) havesuggested the grouping of species of section Algarobia into ‘complexes’ or‘species groups’ principally according to their genetic similarity and geographicdistribution, but also to their habit and resource characters.Prosopis juliflora Swartz DC. and Prosopis pallida (Humbolt & Bonpland exWilld.) H.B.K. were grouped into the ‘P. juliflora–pallida complex’ by Pasieczniket al. (2001), a suggestion also made earlier by Felker (1990). These twospecies occur over a broad geographical area approximately limited by thetropics of Cancer and Capricorn, including Mexico, Guatemala, El Salvador,Honduras, Nicaragua, Costa Rica, Panama, Colombia, Venezuela, Ecuador,Peru and the Caribbean islands. The species of section Algarobia to the northare P. glandulosa Torrey, P. laevigata (Humbolt & Bonpland ex Willd.) M.C.Johnston and P. velutina Wooton, which may be considered a North Americancomplex. To the south of the P. juliflora–pallida complex lie all other species ofsection Algarobia, including P. chilensis (Molina) Stuntz emend. Burkart.The P. juliflora–pallida complex was divided into three geographically distinctgroups, termed ‘races’ by Pasiecznik et al. (2001). Group 1 comprisespopulations in Ecuador and Peru. P. pallida has been identified throughout thisarea while three varieties of P. juliflora have been identified in northern Peruand southern Ecuador (Burkart 1976). Burkart (1976) also reported a possibleP. juliflora · P. pallida hybrid in Ecuador. Populations in the north of this areadisplay some phenotypic characteristics typical of P. juliflora while those in thecentre and south appear to be purely P. pallida. Group 2 comprises populationsof P. juliflora in Colombia, Venezuela and the Caribbean islands. Severalauthorities have included the Caribbean in the native range, and if not nativethey became naturalised in prehistory (Timyan 1996). Group 3 also comprisespopulations of P. juliflora, in the Pacific coastal areas of Central America fromMexico to Panama, with some inland extensions. In the north of this region,populations of P. juliflora are thought to overlap with P. glandulosa andP. laevigata (Pasiecznik et al. 2001). However, the status of P. juliflora inMexico is uncertain (Pasiecznik et al. 2001), although recent work usingmolecular markers is beginning to resolve some of the underlying geneticvariation found here (Jua´rez-Mun˜ oz et al. 2002).Many Prosopis species are valuable multipurpose biotic resources in theirnative range and where introduced, providing timber, firewood, livestock feed,human food, shade, shelter and soil improvement (Harris et al. 1998). Severalspecies, for example the sub-tropical P. chilensis, P. glandulosa and P. velutina,and more importantly, the tropical species, P. juliflora and P. pallida, have beenintroduced in the last 200 years and are now widespread in, for example,Brazil, Sahelian Africa, South Africa, Pakistan, India and Australia. However,