Taxonomic revision of Chaerophyllum hirsutum with molecular markers
Chaerophyllum hirsutum represents a complex of taxa with varying treatments and ranks across floras. Using both morphometric and molecular markers, we assessed the robustness of C. hirsutum var. hirsutum, C. elegans, C. villarsii and C. villarsii var. cicutariiforme. Ten morphometric variables and two ratios were estimated. Based on the sequencing of six plastomes, the rps16 intron   was selected as the more variable region, and sequenced on a broader sampling. Finally, we also sequenced the nrDNA internal transcribed spacer 2 (ITS2) amplicon using Illumina technology to obtain intra-individual allelic diversity. Morphologically, the most easily differentiated taxon was C. elegans, especially using the number of subterminal umbels. The distinction between var. hirsutum and var. villarsii was rather clinal, but mainly based on the degree of carpophore division. Finally, var. cicutariiforme  was less easily distinguishable from the three others, but partly using the carpophore length and the total length of basal leaf blade. The cpDNA rps16 clearly distinguished C. elegans from the three other taxa of C. hirsutum, which rather showed a geographical pattern of cpDNA diversity. The nrDNA ITS2 partially distinguished var. villarsii from the other taxa, without distinction of C. elegans. The present study supports the species differentiation of C. elegans based on both morphology and chloroplast genome. We have opted to gather var. villarsii and var. cicutariiforme within C. hirsutum until further studies reinvestigating these taxa with more resolving markers covering a broader part of the nuclear genome.