Targeted capture of nuclear genes increasingly contributes to unravelling phylogenetic relationships that hitherto remained unresolved because of limitations of traditional Sanger sequencing. In particular, the study of tropical plant families has been compromised because they often rely on highly degraded DNA obtained from herbarium specimens. One such example is the pantropical Ochnaceae, which comprises 33 genera and approximately 550 species, occurring mostly in savannas and moist tropical forests. Here, we developed a set of baits covering about 660,000 bp from 275 nuclear genes used for the targeted enrichment based on all but one genus and more than 250 species. Using this novel dataset, we resolved the phylogenetic backbone of Ochnaceae, including that of Ochninae, and we established new relationships. Most importantly, our findings highlight that the neotropical and palaeotropical taxa of Sauvagesia form independent clades, requiring the re-erection of formerly separate genera. Ouratea and Ochna (both Ochninae), by far the most species-rich genera and represented by 120 and 41 species, respectively, came out as monophyletic. In contrast, the third-most species-rich genus, Campylospermum, is polyphyletic in two distinct clades. Ouratea, the only neotropical genus of Ochninae, was sister to the five palaeotropical genera of this subtribe. The bait kit developed in this study proved to be particularly useful for unravelling relationships within Ochninae, which includes about two-thirds of the species diversity in the family. Keywords baits; hybrid enrichment; Malpighiales; multispecies coalescent approach; remapping strategies; species tree Supporting Information may be found online in the Supporting Information section at the end of the article.

Plastid DNA sequence data have been traditionally widely used in plant phylogenetics because of the high copy number of plastids, their uniparental inheritance, and the blend of coding and non-coding regions with divergent substitution rates that allow the reconstruction of phylogenetic relationships at different taxonomic ranks. In the present study, we evaluate the utility of the plastome for the reconstruction of phylogenetic relationships in the pantropical plant family Ochnaceae (Malpighiales). We used the off-target sequence read fraction of a targeted sequencing study (targeting nuclear loci only) to recover more than 100 kb of the plastid genome from the majority of the more than 200 species of Ochnaceae and all but two genera using de novo and reference-based assembly strategies. Most of the recalcitrant nodes in the family’s backbone were resolved by our plastome-based phylogenetic inference, corroborating the most recent classification system of Ochnaceae and findings from a phylogenomic study based on nuclear loci. Nonetheless, the phylogenetic relationships within the major clades of tribe Ochnineae, which comprise about two thirds of the family’s species diversity, received mostly low support. Generally, the phylogenetic resolution was lowest at the infrageneric level. Overall there was little phylogenetic conflict compared to a recent analysis of nuclear loci. Effects of taxon sampling were invoked as the most likely reason for some of the few well-supported discords. Our study demonstrates the utility of the off-target fraction of a target enrichment study for assembling near-complete plastid genomes for a large proportion of samples.

Ochnaceae is a pantropical family with multiple transoceanic disjunctions at deep and shallow levels. Earlier attempts to unravel the processes that led to such biogeographic patterns suffered from insufficient phylogenetic resolution and unclear delimitation of some of the genera. In the present study, we estimated divergence time and ancestral ranges based on a phylogenomic framework with a well-resolved phylogenetic backbone to tackle issues of the timing and direction of dispersal that may explain the modern global distribution of Ochnaceae. The nuclear data provided the more robust framework for divergence time estimation compared to the plastome-scale data, although differences in the inferred clade ages were mostly small. While Ochnaceae most likely originated in West Gondwana during the Late Cretaceous, all crown-group disjunctions are inferred as dispersal-based, most of them as transoceanic long-distance dispersal (LDD) during the Cenozoic. All LDDs occurred in an eastward direction except for the SE Asian clade of Sauvagesieae, which was founded by trans-Pacific dispersal from South America. The most species-rich clade by far, Ochninae, originated from either a widespread neotropical-African ancestor or a solely neotropical ancestor which then dispersed to Africa. The ancestors of this clade then diversified in Africa, followed by subsequent dispersal to the Malagasy region and tropical Asia on multiple instances in three genera during the Miocene-Pliocene. In particular, Ochna might have used the South Arabian land corridor to reach South Asia. Thus, the pantropical distribution of Ochnaceae is the result of LDD either transoceanic or via land bridges/corridors, whereas vicariance might have played a role only along the stem of the family.