Hybrid capture resolves the phylogeny of Tetradium (Rutaceae) and supports the inclusion of a species from Sulawesi

Abstract

Tetradium, a genus within Rutaceae, comprises nine species found in Eastern and Southeastern Asia, distinguished by their opposite pinnate leaves and apocarpous or subapocarpous gynoecium with follicular fruits. While Hartley's 1981 monograph provided foundational insights, a comprehensive phylogenetic analysis of the genus is lacking. Using next‐generation sequencing (NGS), this study aims to (i) establish an NGS molecular data set for Tetradium, (ii) elucidate interspecific relationships via the hybrid capture method and (iii) investigate the taxonomic status of Euodia meliifolia var. celebica. Our data set comprised 28 samples across nine species, sequenced using Illumina Miseq and Hiseq 4000 platforms, with downstream analyses conducted using the HybPhyloMaker pipeline and ASTRAL. Our findings revealed five main groups supported by both molecular and morphological data, highlighting changes in ovule number and seed functionality. Notably, the hybrid capture method proved invaluable for studying old herbarium specimens. Finally, taxonomic revisions were proposed, including the reclassification of E. meliifolia var. celebica as Tetradium celebicum, the fossil Euodia costata as Tetradium costatum, and the fossil Euodia lignata as Tetradium lignatum. An updated description for T. celebicum, supplemented by a specific identification key, is provided.