Characterization of four wild edible Carduus species from the Mediterranean region via phytochemical and biomolecular analyses.

Carduus species (Compositae) are widely distributed in the Mediterranean area, and traditionally used for both food and medicinal purposes. The hydroalcoholic extracts of four wild edible Carduus species collected in Sardinia (Carduus argyroa Biv., Carduus nutans subsp. macrocephalus (Desf.) Nyman, Carduus pycnocephalus L., Carduus cephalanthus Viv.) were analyzed and characterized by HPLC-PDA-MS/MS and PCR-RFLP of the nrDNA internal transcribed spacer (ITS). Flavonoids and caffeoylquinic acid derivatives were the predominant classes of secondary metabolites characterizing the extracts. The ITS region was sequenced in parallel, and a PCR-RFLP method was applied with three selective restriction enzymes. Statistical analyses, on both chemical and biomolecular results, revealed that individuals clustered according to their taxonomic classification. The combination of the two techniques discriminates the four species within the genus, giving further information on these little-investigated plants, traditionally used in the Mediterranean area and in Sardinia.

Invasional interference due to similar inter- and intraspecific competition between invaders may affect management.

As the number of biological invasions increases, the potential for invader-invader interactions also rises. The effect of multiple invaders can be superadditive (invasional meltdown), additive, or subadditive (invasional interference); which of these situations occurs has critical implications for prioritization of management efforts. Carduus nutans and C. acanthoides, two congeneric invasive weeds, have a striking, segregated distribution in central Pennsylvania, U.S.A. Possible hypotheses for this pattern include invasion history and chance, direct competition, or negative interactions mediated by other species, such as shared pollinators. To explore the role of resource competition in generating this pattern, we conducted three related experiments using a response-surface design throughout the life cycles of two cohorts. Although these species have similar niche requirements, we found no differential response to competition between conspecifics vs. congeners. The response to combined density was relatively weak for both species. While direct competitive interactions do not explain the segregated distributional patterns of these two species, we predict that invasions of either species singly, or both species together, would have similar impacts. When prioritizing which areas to target to prevent the spread of one of the species, it is better to focus on areas as yet unaffected by its congener; where the congener is already present, invasional interference makes it unlikely that the net effect will change.