Evidence of Hybrid Origin for Domesticated Spondias (Anacardiaceae) Taxa from Northeastern Brazil: A Picture of Ongoing Domestication of Fruit Species

Hybridization is considered an important process in plant evolution, especially in the origin domesticated plant taxa, with many crop species being the result of interspecific hybridization events. There are several unidentified lineages of Spondias in the Northeastern region of Brazil known only by vernacular names such as ‘cajaguela’, ‘umbu-cajá’, and ‘umbuguela’. These taxa are often regarded as being of hybrid origin, based on supposedly intermediate morphological features. However, the morphology-based hypotheses of hybrid origin and parentage of these Spondias taxa remains largely untested experimentally. We collected 355 accessions of Spondias including the putative hybrid taxa and both native and introduced species. We then reconstructed phylogenies of plastid and nuclear markers, and also haplotype networks in order to ascertain the genetic affinities between putative hybrids and other Spondias species. All taxa with intermediate morphology were confirmed as hybrids between their putative parental species. All hybrids involving S. purpurea (native to Mexico) appear to be F1 generation. The recently described Spondias bahiensis is shown to have originated from hybridization between S. tuberosa and S. venulosa. The other ‘umbu-cajá’ taxon found in Northeastern of Brazil is revealed to be the result of hybridization between S. mombin and S. tuberosa. Both the northern ‘umbu-cajá’ taxon and S. bahiensis appear to be well-established hybrid lineages and not early generation hybrids. Additionally, some introgression and backcrossing processes between S. bahiensis and one of the parents was also observed. Our findings confirm the hybrid origins of the domesticated Spondias taxa found in Northeastern Brazil.