Floral traits and reproductive biology of two Mediterranean species of Clematis, asynchronous and sympatric, are key food sources for pollinator survival

Abstract

• We reveal the floral trends and reproductive biology of two Mediterranean Clematis species. • Volatile compounds were sampled using a SPME-HS followed by GC–MS. • 90% of the volatile compounds were monoterpenes in both species. • Pollen supply and nectar production are important for pollinators during critical periods. • Hedges plant formations play an essential role in the conservation of pollinators and act as a linking semi-natural environment and farmland. Clematis cirrhosa L. and C. flammula L. (Ranunculaceae) are perennial climbing species, that are sympatric and that bloom in two different seasons: winter and summer. Both have colourful flowers representing the two types of Clematis flowers present in the Western Mediterranean basin: bell-shaped and disc-shaped flowers, respectively. This morphological and positional diversity encourages the comparative analysis of their reproductive biology, as well as the profiles of their floral volatiles. Morphological floral traits and the shape of flowers are different and are highly correlated with the rainy season pollinator's availability. Both species exhibit facultative autogamy. Volatile compounds were extracted using a standardised solid-phase microextraction of headspace (SPME-HS) followed by gas chromatography and mass spectrometry (GC-–MS). The spectrum of flower scents highlights the importance of monoterpenes (93% in C. cirrhosa and 99% in C. flammula ) as the major components identified in both species. The study helps to explain the relationship between the floral shape, the pollination system, and the reproductive characteristics of Clematis . In addition, these two species act as food reservoirs for pollinators supplying pollen and nectar in critical periods of the year when resources are scarce. The two species play an important role in maintaining the populations of Apis mellifera, Bombus terrestris , and other seasonal pollinators.