Delimiting species boundaries is a perennial challenge in the field of systematics. Resolving whether morphological variation is the result of environmental parameters, incipient speciation, or complete speciation is especially challenging when the variation is subtle. Within the perennial endemic North American clade of Apiaceae (PENA) there are numerous examples in which widespread species have subtle geographically defined morphological variants that have typically been recognized at the subspecific rank. The Lomatium foeniculaceum (Nutt.) Coult & Rose species complex is a salient case that has long been treated as a single species with five infrataxa, spanning much of the western United States and western Canada in a morphological continuum: L. foeniculaceum var. foeniculaceum, L. foeniculaceum var. daucifolium (Torr. & A. Gray) Cronquist, L. foeniculaceum var. macdougalii (J.M. Coult. & Rose) Cronquist, L. foeniculaceum var. fimbriatum (W.L. Theob.) B. Boivin, and L. foeniculaceum var. inyoense (Mathias & Constance) B. Boivin. We utilized the Angiosperm353 baits kit to sample nuclear loci from these five taxa to determine if the subspecific taxa formed discrete genetic groups with the molecular data. Groups that were identified were then examined for a combination of morphological and ecological traits that corresponded to these groups and could be used to determine the most appropriate taxonomic ranks of recovered groups. Molecular data recovers six well-supported monophyletic clades and a seventh clade of a single individual. Samples initially identified as L. foeniculaceum var. macdougalii are in two clades with one sister to L. foeniculaceum var. foeniculaceum/L. foeniculaceum var. daucifolium the other sister to L. foeniculaceum var. fimbriatum. Most samples of L. foeniculaceum var. foeniculaceum are in the same clade; others are in the clade with L. foeniculaceum var. daucifolium depending on the analysis. Each clade can be defined with a distinct morphological diagnostic character state. We conclude that molecular data and morphology support the recognition of five distinct species within the complex: L. inyoense Mathias & Constance, L. macdougalii J. M. Coult. & Rose, L. fimbriatum (W.L. Theob.) Botello & J.F. Sm., L. semivaginatum Botello & J.F. Sm., and L. foeniculaceum with two varieties retained, L. foeniculaceum var. foeniculaceum and L. foeniculaceum var. daucifolium. The data suggest that the Continental Divide has been influential in the evolution of these species, acting as an effective barrier facilitating speciation.

Premise of research. Shared ancestry and convergent/parallel evolution are the two primary causes of morphologically similar species occurring in similar climatic niches. Alpine habitats harbor a unique biodiversity that is often characterized by many convergences in life-forms, such as cushion and rosulate habits. Three species of Lomatium (L. greenmanii, L. erythrocarpum, and L. oreganum) are high-alpine specialists endemic to the Wallowa and Elkhorn Mountains of northeastern Oregon. Earlier studies suggested that two of these species might be sister taxa, but because of the prevalence of convergence in alpine habitats and recent studies that have highlighted morphological homoplasy among Lomatium species, this hypothesis warrants reconsideration. Methodology. Phylogenetic analysis of 209 individuals representing 79 taxa belonging to subfamily Apioideae (Apiaceae) was used to investigate the evolutionary origins of three alpine-endemic species of Lomatium. A principal components analysis based on BioClim variables was used to further investigate species climatic niches. Pivotal results. The three alpine-endemic species of Lomatium from northeastern Oregon represent three independent origins of alpine adaptations rather than a single or two alpine radiations, as previously suggested. Conclusions. Convergence and parallelism are especially common in alpine habitats and among Lomatium species, a finding confirmed by this study. This study unveils unpredicted phylogenetic diversity in the Wallowa and Elkhorn Mountains, which, therefore, calls for appropriate conservation measures to protect these distinct evolutionary lineages.