The cactus family (Cactaceae) is a large family of approximately 2000 species restricted to the American continent, but now cultivated all over the world. Although most cacti are found in deserts, they can also prosper as epiphytes in humid places. The region comprising Peru and Bolivia has the second highest species diversity for Cactaceae in the world and also may represent a possible site of origin for the family. In spite of the large size and ecological importance of Cactaceae, few studies have examined relationships in the family. Most South American species of cacti belong to tribe Trichocereeae, with about 80% of them endemic to their respective countries. Relationships and species boundaries among members of Trichocereeae are poorly understood. Trichocereeae show great morphological variability and complex reproductive patterns, traditionally attributed to phenomena such as hybridization, polyploidy (or genome doubling), and vegetative propagation. The Trichocereeae, and Haageocereus in particular, are becoming more and more vulnerable to human disturbance given that the largest and most populated cities in most South American countries are located in the natural habitats of these cacti. A phylogeny is a crucial first step to obtain a better understanding of the biology of these organisms and to facilitate subsequent ecological and/or conservation studies. The phylogeny of tribe Trichocereeae will be used as a framework for: 1) resolving relationships among genera in Trichocereeae; 2) resolving relationships among species of Haageocereus; 3) determining the presence and importance of hybridization and polyploidy in Haageocereus and other Trichocereeae; 4) examination of biogeographic patterns in the group; 5) examination of genetic diversity in endangered species of Haageocereus. Haageocereus, perhaps the most morphologically diverse genus in Trichocereeae, will serve as a model system and will be investigated in detail at the species and population level employing DNA sequencing and microsatellite techniques. Studies on Trichocereeae will continue to have educational impact through dissemination of the results through publications, the Trichocereeae website, conferences, seminars and courses offered at universities and botanical institutions located in cacti-rich areas. Importantly, the governmental institution INRENA (National Institute of Natural Resources) will use this work on the conservation status of endemic Cactaceae and accompanying database (Arakaki and Ostolaza 2005 in press) to establish management policies for Peruvian cacti. The project will also involve collaboration with botanists in Bolivia and Chile.
