Carpological and receptacular morpho-anatomical characters of Inula, Dittrichia, Limbarda and Pulicaria species (Compositae, Inuleae): Taxonomic implications

• Characters of fruit and receptacle, specific to genera and species, are described.
• Criteria useful for delimitation of frequently misidentified taxa are provided.
• Distribution of fruit sclerenchyma and receptacle features tend to be diagnostic for genera.
• Fruit and receptacle morpho-anatomy support segregation of I. helenium into a separate genus.

Genus Inula L. is paraphyletic and heterogeneous with respect to several diverse characters, which makes delimiting taxa difficult. Dittrichia Greuter, Limbarda Adans. and Pulicaria Gaertn. were previously located in different sections within Inula, and subsequently segregated into separate genera. According to the latest molecular phylogenetic analyses based on plastid and nuclear DNA sequence data, supported by morphological and karyological data, it is suggested that type species of genus, Inula helenium L., should be separated from the remaining species to form a separate genus. The goals of this research are to (1) perform comparative micro-morphological and anatomical analysis of fruit and receptacle of species belonging to Inula, Pulicaria, Dittrichia and Limbarda genera in order to estimate their systematic value; (2) define further characters that would be useful in taxonomic delimitation of species that are often misidentified due to their morphological similarities; (3) investigate whether all these characters support the segregation of I. helenium into a separate genus. Using stereoscopic, light and scanning electron microscope, micro-morphological and anatomical characters of cypsela and receptacle were revealed. Cross sections of mature fruit were obtained using cryotechnic procedure. This study pertains to the evaluation of examined characters using correspondence analysis. The species’ characters, as well as those specific to the genera are identified and described. The findings reveal that the organisation of sclerenchyma tissue in a fruit and receptacle characteristics are features that tend to be diagnostic for genera. The results yielded by this study provide valuable criteria for delimitation of taxa belonging to Compositae tribe Inuleae, which are often misidentified due to their morphological similarities. Our results, based on anatomical and micro-morphological characteristics of the fruit and receptacle, also revealed that I. helenium can be distinguished as a separate taxon with equally small percentage of statistical support as Dittrichia, Limabarda and Pulicaria had.