Geometric morphometrics of corolla shape in Campanula (Campanulaceae) from Cabo Verde archipelago

In the Cabo Verde archipelago, Campanula spp. (bellflowers) are currently represented by four endemic species restricted to mountainous islands (C. bravensis, C. feijoana, C. hortelensis and C. jacobaea), all of which are known for high floral polymorphism. Diagnostic features of the corolla often differ from original descriptions, bringing into question their taxonomic delimitation. Based on the variations in the corolla shape observed during fieldwork, eight morphogeographical entities were distinguished among the taxa in the archipelago. Geometric morphometrics was used to quantify and examine these floral variations. Corolla morphology of 221 photographed flowers was captured by 2D landmarks and semi-landmarks configurations and analysed with canonical variate analysis. The results show agreement between morphological groupings and their geographical ranges. For most entities, the geographical origin may be determined with accurate morphological examination of the flower. In this case, the corolla shape proves to be a taxonomically discriminant trait. Furthermore, the terminology used until now to characterize these different floral forms is discussed. The present study contributes significantly to clarifying the floral polymorphism in Cabo Verdean Campanula and suggests that taxonomic revision of this group is necessary.