Boehringer Ingelheim (Mexico)

Summary⍰ Orchids constitute one of the most spectacular radiations of flowering plants. However, their geographical origin, historical spread across the globe, and hotspots of speciation remain uncertain due to the lack of a broad phylogenomic framework.⍰ We present a new Orchidaceae phylogeny based on high-throughput and Sanger sequencing datasets, covering all five subfamilies, 17/22 tribes, 40/49 subtribes, 285/736 genera, and ∼7% (1,921) of the currently 29,524 accepted species. We then use it to infer geographic range evolution, diversity, and speciation patterns by adding curated geographical distribution data through the World Checklist of Vascular Plants.⍰ Orchid’s most recent common ancestor is traced back to the Late Cretaceous in Laurasia. The modern Southeast Asian range of subfamily Apostasioideae is interpreted as relictual, matching the history of numerous clades that went extinct at higher latitudes following the global climate cooled during the Oligocene. Despite their ancient origins, modern orchid species’ diversity mainly originated over the last 5 Ma, with the fastest speciation rates found in south-eastern Central America.⍰ Our results substantially alter our understanding of the geographic origin of orchids, previously proposed as Australian, and further pinpoint the role of Central American as a region of recent and explosive speciation.

Poor morphological and molecular differentiation in recently diversified lineages is a widespread phenomenon in plants. Phylogenetic relationships within such species complexes are often difficult to resolve because of the low variability in traditional molecular loci, as well as various other biological phenomena responsible for topological incongruence such as ILS and hybridization. In this study, we employ a Genotyping-by-sequencing (GBS) approach to disentangle evolutionary relationships within a species complex belonging to the Neotropical orchid genus Cycnoches. The complex includes seven taxa distributed in Central America and the adjacent Chocó biogeographic region, nested within a clade estimated to have first diversified in the early Quaternary. Previous phylogenies inferred from a handful of loci failed to provide support for internal relationships within the complex. Our Neighbor-net and coalescent-based analyses inferred from ca. 13,000 GBS loci obtained from 31 individuals belonging to six of the seven traditionally accepted Cycnoches species provided a robustly supported network. The resulting three main clades are corroborated by morphological traits and geographical distributions. Similarly, Maximum Likelihood (ML) inferences of concatenated GBS-loci produced results comparable with those derived from coalescence and network-based methods, albeit always with poor statistical support. The low support evident in the ML phylogeny might be attributed to the abundance of uninformative GBS loci, which can account for up to 50% of the total number of loci recovered. The phylogenomic framework provided here, as well as morphological evidence and geographical patterns, suggest that the six entities previously thought to be different species might actually represent only three distinct segregates. Our study is the first to demonstrate the utility of GBS data in phylogenomic research of a very young Neotropical plant clade (~2 Ma), and it paves the way for the study of the many other species complexes that populate the species-rich orchid family.