Resolving taxonomic uncertainty and exploring evolutionary relationships in the <i>Cymopterus terebinthinus</i> (Apiaceae) species complex Wiley 05/26/2025 10596449 10.1002/tax.13344 TAXON 0040-0262 Annie TaylorDon MansfieldSven BuerkiMary Ann FeistMark DarrachJames F Smith Abstract

Speciation processes in plants can be difficult to evaluate, but are essential to understanding evolutionary processes that lead to diversification. Determining the juncture at which a genetically and/or morphologically divergent population can be reliably considered a separate species is often challenging. This is particularly so with respect to recent divergences amongst closely related taxa wherein factors such as incomplete lineage sorting may yield confounding results. Taxa in theCymopterus terebinthinus(Apiaceae) species complex have long puzzled botanists. Named entities in this group display similar, yet apparently distinct morphologies that have been classified as varieties under various generic names highlighting long‐standing nomenclatural instability. Previous phylogenetic studies have challenged the monophyly of this complex. This study aims to clarify taxonomic boundaries and infer evolutionary relationships among the fourC.terebinthinusvarieties andC.petraeusby applying phylogenetic inference and incorporating ecological, morphological, and geographical evidence. We sampled from populations of all varieties ofC.terebinthinusandC.petraeusfor target capture with the Angiosperms353 bait kit. We performed phylogenetic analyses with maximum likelihood (RAxML and IQ‐TREE) and coalescent‐based phylogenetic analysis (ASTRAL). We also conducted principal component analysis of soil samples and climatic variables. We find thatC.terebinthinusand its varietal infrataxa comprise a monophyletic clade that includesC.petraeus. Clade groupings correspond to previous taxonomic assignments and morphology. Clades are often closely associated with geographical variables and at times correlated with ecological variables. Exceptions to this are here attributed to various evolutionary factors that often confound other phylogenetic analyses such as incomplete lineage sorting, introgression, and paralogous loci. Our findings suggests that geographical factors might play a major role in genetic and morphological differentiation in this complex. Despite finding well‐supported clades that correspond to defined morphological characters; further sampling amongC.petraeuspopulations is required to make taxonomic decisions.

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