Disentangling complex relationships and disjunctions in western Camassia: Integrating multiple criteria to resolve...

Understanding genetic and morphological variability helps efforts to sustain landscapes and develop effective species concepts for resolving difficult groups. To unravel puzzling relationships and range disjunctions, we applied morphometrics, phenology, phylogenetics and population genetics in Camassia species with cultural, ecological, and conservation value, asking: Do the unusual Camassia populations in northeastern California represent previously unrecognized, disjunct C. howellii? Do C. howellii, C. leichtlinii, and C. quamash maintain diagnostic features in allopatry or sympatry? Are C. quamash subsp. breviflora and subsp. linearis taxonomically distinct?

We evaluated 34 Camassia populations in situ for morphometric traits, phenology, and habitat type, collecting tissue for population microsatellite and phylogenetic analyses (rpl16, trnD-trnT). Fieldwork and genetic analyses of Camassia species allowed hypothesis testing of all criteria.

Oregon and California populations of C. howellii shared 94-95% morphospace but differed significantly from C. leichtlinii and C. quamash, primarily in having more basal leaves, subglobose fruits, and smaller flowers that open in mid-late afternoon, closing at sunset without reopening. Both microsatellite and phylogenetic data indicated separation of the three species, with slight genetic differentiation between the disjunct populations of C. howellii. Subspecies of C. quamash differed morphologically and genetically, with clear phylogenetic separation.

Integrative approaches proved effective, affirming disputed species identities and upholding subspecific status for C. quamash subsp. linearis. For C. howellii, population genetic differentiation between disjunct regions appears congruent with phylogenetic analyses. Slight morphological differentiation of Oregon and California populations is consistent with geographic isolation, implying subspecific genetic divergence worthy of future study.