Elevation-Driven Morphological Variation in Dianthus virgineus L. s.l. in the Southern Apennine: A Functional...

Traditional morphological frameworks within the Dianthus virgineus complex have recognized two closely related taxa, D. longicaulis and D. brachycalyx, distributed along elevational gradients in the central and southern Apennines. However, recent genomic evidence has questioned their taxonomic independence, suggesting that morphological differentiation may reflect environmentally structured variation rather than distinct evolutionary lineages. Here, we adopted an integrative trait-based approach to evaluate whether phenotypic discontinuities occur between low- and high-elevation populations of D. virgineus in the southern Apennines. We analyzed morphological traits, functional traits, and fluctuating asymmetry across 12 populations spanning a broad elevation range (500-2200 m a.s.l.), treating elevation as a proxy for ecological variation. Morphological differentiation was significant but continuous along the elevational gradient, with no evidence of discrete phenotypic clusters corresponding to traditionally recognized taxa. Functional traits showed coordinated shifts consistent with increasing stress tolerance at higher elevations, and multivariate analyses revealed significant congruence between morphological and functional trait spaces. Patterns of fluctuating asymmetry decreased with elevation, suggesting enhanced developmental stability under persistent environmental constraints. Together, these results indicate that the phenotypic combinations historically used to delimit D. longicaulis and D. brachycalyx are best interpreted as environmentally structured morphotypes within D. virgineus, rather than taxonomically independent entities. Our findings highlight how integrative analyses combining morphology, functional ecology, and developmental stability can clarify the ecological and evolutionary significance of phenotypic variation in polymorphic plant complexes and help prevent taxonomic oversplitting.