Domestication and proto-domestication in fruit trees lead predictably to changes in fruit and seed traits. These changes are likely in turn to influence life history and fitness in the original wild context. In areas where wild populations persist in close proximity to proto-domesticated genotypes, comparisons between the two 1) reveal what traits humans may be selecting on, and 2) provide an opportunity to study the ecological significance of those traits in the wild. In Panama, the caimito tree, Chrysophyllum cainito, is commonly cultivated in home gardens while still widespread in tropical forests across the Pacific slope. We compared fruits and seeds of cultivated individuals with those from wild populations. Seed germination experiments and transplant experiments in the forest understory were used to explore the ecological significance of differences between fruits and seeds of cultivated and wild trees.
Results/Conclusions
We found a strong signature of domestication in fruit size and allometry (larger fruits with reduced allocation to exocarp), in seed number and size (more and bigger), and in chemistry related to flavor (lower in phenolics and less acidic). We found evidence for a loss of desiccation resistance, more rapid germination, and a concomitant loss of seed defenses in domesticated genotypes. Both cultivated and wild groups showed considerable variation for all traits. In the forest understory, transplanted seeds of wild individuals had higher germination success and were capable of germinating straight from dried fruits, while domesticated were not. However, transplanted seedlings derived from domesticated genotypes survived as well and grew as well as wild genotypes. Thus, domestication has led to reduced fitness for some, but not all, aspects of early establishment in this tropical tree. Gene flow across the rural-wild boundary in central Panama has the potential to reduce the fitness of wild populations of C. cainito, even when those populations are in protected areas.
