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 origins of domesticated plant taxa, with many crop species being the result of interspecific hybridization events. There are several unidentified lineages of <i>Spondias</i> 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 <i>Spondias</i> taxa remain largely untested experimentally. We collected 355 accessions of <i>Spondias</i>, including <i>S. bahiensis</i>, other putative hybrid taxa, and both native (<i>S. mombin</i>, <i>S. tuberosa</i>, and <i>S. venulosa</i>) and introduced (<i>S. purpurea</i>) species believed to be the parental taxa. We then reconstructed phylogenies of plastid and nuclear markers and haplotype networks in order to ascertain the genetic affinities between putative hybrids and other <i>Spondias</i> species. All taxa with intermediate morphology were confirmed as hybrids between their putative parental species. All hybrids involving <i>S. purpurea</i> (native to Mexico) appear to be F₁ generation. The recently described <i>S. bahiensis</i> is shown to have originated from hybridization between <i>S. tuberosa</i> and <i>S. venulosa</i>. The other 'umbu-cajá' taxon found in Northeastern Brazil is revealed to be the result of hybridization between <i>S. mombin</i> and <i>S. tuberosa</i>. Both the northern 'umbu-cajá' taxon and <i>S. bahiensis</i> appear to be well-established hybrid lineages and not early-generation hybrids. Additionally, some introgression and backcrossing processes between <i>S. bahiensis</i> and one of the parents was also observed. Our findings confirm the hybrid origins of the domesticated <i>Spondias</i> taxa found in Northeastern Brazil.