Morphometry does not support current taxonomic diversity of central Mediterranean carnations (Dianthus virgineus complex)

Describing populations with peculiar phenotypic features as new taxa can lead to taxonomic inflation, hampering conservation and ecological studies. Here, we tested the current taxonomy of the Dianthus virgineus complex, a diverse group of wild carnations that may be taxonomically inflated. We conducted a morphometric study including 28 characters acquired from all the 21 taxa occurring in the central Mediterranean, for a total of 73 populations and 1,299 individuals. We conducted Gaussian mixture model-based clustering to detect morphological groups throughout the study area and to assess the support of different grouping scenarios. We also characterized and tested climatic differences among groups belonging to the best-supported scenarios. The current taxonomy is the least supported scenario, whereas a hypothesis based on 10 groups, delineated by the unsupervised analysis, is the best supported, albeit the boundaries among these clusters are not always clear. Significant climatic differences were detected only among morphotypes occupying the extremes of the variation of the complex. A geographical delimitation is still more supported than the current taxonomic setting, reflecting a significant climatic difference among the two geographical clusters. Our results support a phenotypic continuum and an overall taxonomic inflation within the Dianthus virgineus complex in the central Mediterranean.