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Two cryptic species of California mustard within Caulanthus lasiophyllus
Author(s) -
Whittall Justen B.,
Butler Timothy M.,
Dick Cynthia,
Sandel Brody
Publication year - 2020
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/ajb2.1562
Subject(s) - biology , species complex , evolutionary biology , clade , internal transcribed spacer , range (aeronautics) , phylogeography , introgression , ribosomal rna , phylogenetics , genetics , gene , phylogenetic tree , materials science , composite material
Premise Cryptic species are evolutionarily distinct lineages lacking distinguishing morphological traits. Hidden diversity may be lurking in widespread species whose distributions cross phylogeographic barriers. This study investigates molecular and morphological variation in the widely distributed Caulanthus lasiophyllus (Brassicaceae) in comparison to its closest relatives. Methods Fifty‐two individuals of C. lasiophyllus from across the species’ range were sequenced for the nuclear ribosomal internal transcribed spacer region (ITS) and the chloroplast trn L‐F region. A subset of these samples were examined for the chloroplast ndh F gene. All 52 individuals were scored for 13 morphological traits, as well as monthly and annual climate conditions at the collection locality. Morphological and molecular results are compared with the closest relatives —C. anceps and C. flavescens —in the “Guillenia Clade.” To test for polyploidy, genome size estimates were made for four populations. Results Caulanthus lasiophyllus consists of two distinct lineages separated by eight ITS differences—eight times more variation than what distinguishes C. anceps and C. flavescens . Fewer variable sites were detected in trn L‐F and ndh F regions, yet these data are consistent with the ITS results. The two lineages of C. lasiophyllus are geographically and climatically distinct; yet morphologically overlapping. Their genome sizes are not consistently different. Conclusions Two cryptic species within C. lasiophyllus are distinguished at the molecular, geographic, and climatic scales. They have similar genome sizes and are morphologically broadly overlapping, but an ephemeral basal leaf character may help distinguish the species.