A Revised Phylogeny of the Mentha spicata Clade Reveals Cryptic Species

Abstract

The genus Mentha is taxonomically and phylogenetically challenging due to complex genomes, polyploidization and an extensive historical nomenclature, potentially hiding cryptic taxa. A straightforward interpretation of phylogenetic relationships within the section Mentha is further hindered by dominant but outdated concepts on historically identified hybrid taxa. Mentha spicata is traditionally considered to be of hybrid origin, but the evidence for this is weak. Here, we aim to understand the phylogenetic relationships within the section Mentha using large sample sizes and to revisit the hybrid status and identity of M. spicata. We show that two of three traditional species in the subsection Spicatae are polyphyletic, as is the subsection as a whole, while the real number of cryptic species was underestimated. Compared to previous studies we present a fundamentally different phylogeny, with a basal split between M. spicata s.s. and M. longifolia s.s. Cluster analyses of morphological and genotypic data demonstrate that there is a dissociation between morphologically and genotypically defined groups of samples. We did not find any evidence that M. spicata is of hybrid origin, and we conclude its taxonomic status should be revised. The combination of genetic and phenotypic information is essential when evaluating hyperdiverse taxonomic groups.

Challenges in Medicinal and Aromatic Plants DNA Barcoding—Lessons from the Lamiaceae

“…However, in a recent study no evidence was found that M . spicata is of hybrid origin and revealed that many cryptic species were underestimated in subsection Spicatae [ 131 ]. Spearmint is widely grown throughout all regions of the world and the leaves possess a characteristic aromatic odour and pungent taste.…”

“…Indeed, plasticity is highly known in Mentha [ 156 , 157 ], which confounds morphological identification. Complex morphological, chemical, and molecular diversity in mints have already been described in many studies, e.g., [ 126 , 131 , 158 , 159 , 160 , 161 , 162 , 163 , 164 , 165 , 166 ]. Despite the enormous amount of data gathered, however, there is still need of taxonomic revisions within the genus.…”

“…Despite the enormous amount of data gathered, however, there is still need of taxonomic revisions within the genus. In the recent revised phylogenetic analysis [ 131 ] the origin of M . spicata as hybrid was not supported and hidden cryptic taxa were detected in the genus.…”

Assessment of variability among morphological and molecular characters in wild populations of mint [Mentha longifolia (L.) L.] germplasm

“…Additionally, the molecular data in conjunction with data generated on morphological variability of current taxa will also be helpful in establishing inter- and intra-population phylogenetic relationships. Though extensive work in this line has been carried out for horsemint germplasm of Iran, Egypt, France, Belgium, Netherlands, Switzerland, Denmark ( Harley and Brighton, 1977 , Panjeshahin et al, 2018 , Choupani et al, 2019 , Soilhi et al, 2020 , Yaghini et al, 2020 , Heylen et al, 2021 ), limited data are on record regarding genetic diversity of Indian horsemint accessions ( Khanuja et al, 2000 , Shasany et al, 2005 ), however nothing is on record from Jammu province. Present study is a first attempt of assessing genetic diversity among different M. longifolia populations from varying altitudinal ranges (sub-tropical to temperate) of Jammu province and for having proper programme on breeding and conservation of its elite genotypes (producing more herbage).…”

Effect of Alginite on Some Antioxidant Indexes in Extracts of Two Variants of Mentha and Their Toxicity

“…Several aromatic species of mint contain significant amounts of essential oil thus are economically important (Tucker and Naczi, 2006). The taxonomic and phylogenetic classification of the genus Mentha is very complicated and unclear due to the hyperdiverse of this group of plants (Heylen et al, 2021). Jedrzejczyk and Rewers (2018) summarize the problems with the taxonomic assignment of Mentha species to the following points: a) the existence of variation in basic chromosome number, b) frequent interspecific hybridization, c) cytomixis, d) polymorphism in morphology, e) essential oil composition under different environmental conditions, f) colonial mutant propagation, and g) the occurrence of polyploids, aneuploids, and nothomorphs.…”