Spondias purpurea L. (known locally as jocote, ciruela mexicana, or hog plum) is a small (3–10 m) tree native to the tropical dry forests of Mexico and Central America (34–39). Jocotes are cultivated throughout the tropics and subtropics for their fruits, which are eaten fresh, sold in local markets, and made into jams and beverages (34, 35). The majority of trees are found in backyard gardens and living fences, although some formal cultivation exists in orchards (39). Jocotes are propagated vegetatively from large branch-size cuttings. The existence of at least 180 common names for the species suggests that jocotes have been used by many cultures, and that there is considerable variation within the species (40). Cultivated, mature fruits vary widely in color (green, yellow, orange, red, violet), size (3–5.5 cm long), texture (chalky, juicy), and taste (sweet, acidic) (39). At the time of the European colonization, jocotes were grown widely from Mexico to the northern regions of South America, as described by the first chroniclers of the region (39).
Today, wild jocote populations are found in the fragmented tropical dry forests of Mexico and Central America (36). The native habitat of wild jocotes is severely restricted; it is estimated that 41, 42). Fruits of wild jocotes are usually bright red (A.M., personal observation). They are smaller and more acidic than the cultivated fruits, with considerably less flesh surrounding the seed. Unlike cultivated populations, wild jocotes reproduce from seed and native populations are age-structured with a variety of juvenile and mature individuals present. The contrast in morphology and method of reproduction between wild and cultivated jocotes indicates that S. purpurea is a species that has been altered genetically during the course of domestication. During this process, humans have selected for trees that bear large, fleshy, sweet fruits, and that can be reproduced easily from cuttings.
The genus Spondias L. comprises ≈17 species including seven taxa in the Neotropics and ≈10 species in the Asian tropics (refs. 43–45 and D. Daly and J. D. Mitchell, personal communication). Nearly all Spondias species have a fibrous endocarp and leaflets with an intramarginal vein (45). Neither the relationship of Spondias to closely allied genera nor the relationships among the species of Spondias are well understood (46).
Spondias purpurea is one of three Spondias species native to Mexico and Central America. Spondias mombin L. var. mombin (jobo) is a widespread taxon occuring from Mexico to Paraguay (47). Native to the tropical wet forests, S. mombin var. mombin is a large tree that grows to a height of 30 m. Spondias mombin var. mombin differs from S. purpurea in flower and fruit color, inflorescence structure, leaflet size and number, and bark characteristics (37). In Mesoamerica, S. mombin var. mombin is cultivated occasionally for its fruits and in living fences, although it is not nearly as common as the cultivated jocotes. The third native Spondias species in Mesoamerica is Spondias radlkoferi Donn. Sm., is morphologically similar to S. mombin var. mombin, although it is distinct in fruit shape and flowering time (48). It is rarely cultivated.
In this study, we apply a phylogeographic approach based on chloroplast sequence data to investigate the geographic origins of domesticated jocotes in Mesoamerica and to examine the changes in genetic diversity associated with domestication. Our objectives are to (i) identify the ancestors of the cultivated jocotes, (ii) document the impact of domestication on the diversity of trnG–trnS sequences of S. purpurea, and (iii) to discern one (or more) geographic regions within Mesoamerica where cultivated jocotes originated.
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