A new species of Trechus Clairville, 1806 (Coleoptera: Carabidae: Trechinae) from the Mesovoid Shallow Substratum of the Cantabrian Mountains (Northern Iberian Peninsula)

SummarySamplings in the Mesovoid Shallow Substratum (MSS) in the Cantabrian Mountains (northern Spain) resulted in the capture of 216 specimens of Trechus ground beetles (Coleoptera, Carabidae, Trechinae) resembling Trechus gloriensis Jeanne, 1970. A detailed study based on external morphology, male and female genitalia, and extensive morphometric analyses (ANOVA/ANCOVA, CDA, PCA, ANOSIM and Mantel tests) showed that three eastern populations represent a new species, Trechus paragloriensis n. sp., whereas the western population (type locality of T. gloriensis) corresponds to T. gloriensis. External morphology exhibits a west–east clinal pattern strongly correlated with geographic distance, but with broad overlap between species. In contrast, the aedeagus shows discrete and diagnostic differences in size, proportional development, curvature of the median lobe, and configuration of the endophallus, allowing unequivocal species delimitation. The results indicate that historical connectivity among MSS habitats was followed by population fragmentation, with T. gloriensis undergoing accelerated divergence at the western end of the former cline. The capture of both species in the MSS highlights the importance of this habitat for revealing hidden diversity and re-evaluating the autoecology of Iberian ground beetles.