Inflorescence scents of Calendula maritima, C. suffruticosa subsp. fulgida, and their hybrid

Premise of research. Hybridization is an important driver of plant evolutionary processes. By attracting the same pollinators to different species, floral scents may be involved in the formation of hybrids and breakdown of species boundaries. In contrast, by attracting a different suite of pollinators to hybrids and their parents, floral scents are believed to contribute to speciation processes initiated by hybridization events. Scents may or may not differ between the hybrids and their parents, but little is known about the scent chemistry of parental species and their hybrids. Methodology. We studied the inflorescence scents of parental Calendula maritima and C. suffruticosa subsp. fulgida (henceforth, C. fulgida) and a morphologically intermediate hybrid. Scents were collected by dynamic headspace and analyzed by thermal desorption-gas chromatography/mass spectrometry. Insects visiting inflorescences of the three taxa were also captured. Pivotal results. Calendula maritima and C. fulgida emitted different absolute amounts of scent; the hybrid released intermediate amounts of scent. The scents of the parental and hybrid taxa were all dominated by monoterpenes, with several compounds in common among the taxa. Nevertheless, the three taxa showed differences in qualitative and semiquantitative scent patterns. Calendula maritima emitted more and a higher amount of sesquiterpenes than the other taxa. The hybrid was overall more similar in scent properties to C. fulgida than it was to C. maritima. Conclusions. The overlap in scent compounds among the taxa may be responsible for attraction of the same insect pollinators, resulting in interspecific pollen transfer between the parents and the formation of hybrids. Indeed, preliminary observations revealed that all three taxa are visited by Panurgus siculus bees (Andrenidae).