Biology subjects

Smidt, E.

Publications and source records attributed to Smidt, E..

4 recordsLinked to original sources

bioRxiv2026

Dissetangling the Vine: Phylogenomics and Historical Biogeography of Vanilla (Orchidaceae)

Renowned for its aromatic fruits and economic importance, the genus Vanilla poses longstanding taxonomic and phylogenetic challenges. Despite recent molecular studies, a comprehensive species tree is lacking, and the evolutionary processes and historical patterns shaping the genus remain poorly understood. We present a new, comprehensive phylogenomic framework for Vanilla, based on 349 low-copy nuclear genes and 76 plastid loci from the Angiosperms353 probe set, which we used to infer evolutionary relationships, assess cyto-nuclear and gene-species tree discordance, and thoroughly investigate its historical distribution and diversification. Sampling 43% of the genus, our framework resolves phylogenetic uncertainties, clarifies major clades, confirms prior hypotheses, and reveals novel placements, including V. planifolia and Vanilla subg. Gondwana. Discordances are primarily driven by incomplete lineage sorting, particularly in the vanillin-producing clade, with evidence of both ancient and recent hybridization, including a natural hybrid from the Yucatan Peninsula. Biogeographic analyses indicate a Guiana Shield origin ([~]30 Mya), Amazonia as a major diversification source, the Andes as a permeable barrier, and Central America as the main diversification sink. This study provides a robust evolutionary framework for Vanilla, supporting taxonomic revisions, comparative trait analyses, and a deeper understanding of the processes shaping this economically and biologically important orchid genus.

evolutionary biology↗

bioRxiv2023

The Origin And Speciation Of Orchids

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. Orchids 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.

evolutionary biology↗

bioRxiv2017

From tree tops to the ground: reversals to terrestrial habit in Galeandra orchids (Epidendroideae: Catasetinae)

The colonization of the epiphytic niche of tropical forest canopies played an important role in orchids extraordinary diversification in the Neotropics. However, reversals to the terrestrial habit occurred sparsely in species of Epidendroideae. To better understand which factors might have been involved in reversals to terrestrial habits in the predominantly epiphytic Epidendroideae, we investigate Galeandra diversification in time and space. We hypothesized that the reversal to the terrestrial habitat is linked to the origin of open vegetation habitats in South America. We generated a time-calibrated phylogeny based on a matrix of 17 out of 20 species of Galeandra plus outgroups and seven DNA markers. We found that Galeandra originated towards end of the Miocene, about 10 Ma in Amazonia (including the Guiana Shield). The terrestrial clade originated synchronously with the rise of dry vegetation biomes, suggesting that aridification during the last 5 million years dramatically impacted the diversification of epiphytic lineages in the Neotropics. Habit is correlated with floral spur lengths and geographic range size. The longer spurs and narrower ranges are found in epiphytic species: probably adapted to a specialized pollination mode, associated to the long-tongued Euglossini bees, which also prefer forested habits. The terrestrial species presents variable floral spurs and wide distribution ranges, with evidence of self-pollination, suggesting the loss of specialized pollination system and concomitant range expansion.

evolutionary biology↗

bioRxiv2017

Multiple Geographical Origins of Environmental Sex Determination enhanced the diversification of Darwins Favourite Orchids

Environmental sex determination (ESD) - a change in sexual function during an individual life span driven by environmental cues - is an exceedingly rare sexual system among angiosperms. Because ESD can directly affect reproduction success, it could influence diversification rate as compared with lineages that have alternative mating systems. Here we test this hypothesis using a solid phylogenetic framework of Neotropical Catasetinae, the angiosperm lineage richest in taxa with ESD. We assess whether gains of ESD are associated with higher diversification rates compared to lineages with alternative systems while considering additional traits known to positively affect diversification rates in orchids. We found that ESD has evolved asynchronously three times during the last ~5 Myr. Lineages with ESD have consistently higher diversification rates than related lineages with other sexual systems. Habitat fragmentation due to mega-wetlands extinction, and climate instability are suggested as the driving forces for ESD evolution.

evolutionary biology↗