Ecological niche divergence and specialization in Dianthus pseudocrinitus, a neo-endemic species: ecological evidence challenges sister-taxon delimitation

Clarifying species boundaries within taxonomically complex groups like Dianthus is paramount for understanding evolutionary processes and biodiversity. This study employed a spatially explicit, integrative ecological approach to assess the niche dynamics of Dianthus pseudocrinitus Behrooz. & Joharchi, a neo-endemic species with debated taxonomic status, alongside Dianthus crinitus subsp. turkomanicus (Schischk.) Rech. f. and Dianthus orientalis subsp. stenocalyx (Boiss.) Rech. f. in northeastern Iran. Utilizing high-resolution environmental variables (bioclimatic, soil, NDVI, topographic) within ecological niche modeling, multivariate analyses (MANOVA, LDA), hypervolume-based quantifications, and density overlap metrics, I demonstrated notable and statistically significant ecological niche differentiation among the three taxa. These findings suggested soil characteristics as the likely primary drivers of niche segregation, with NDVI also playing a potentially important role. Crucially, D. pseudocrinitus exhibited a substantially narrower ecological niche (478.33 units, 18.23–22.66%) and minimal overlap with its congeners (Jaccard indices ≤ 0.162), providing strong ecological indications of its distinct species status despite morphological similarities and geographic proximity, and supporting its previously described functional divergence. The strong ecological segregation and narrow niche of D. pseudocrinitus relative to its geographically adjacent congeners provide compelling evidence for parapatric speciation. This pattern of strong fine-scale ecological divergence, alongside some broader bioclimatic niche conservatism, highlights the dynamic interplay of factors shaping species boundaries. The results underscore the potential importance of microhabitat specialization and local adaptation in driving diversification in complex montane environments and advocate for integrative taxonomic approaches to resolve intricate delimitation challenges.