Comparative floral morphometrics in day-flowering, night-flowering and self-pollinated Caryophylloideae (Agrostemma, Dianthus, Saponaria, Silene, and Vaccaria)

Abstract

Morphological variation of flowers with different pollination modes was studied in 53 species representing five genera (Agrostemma, Dianthus, Saponaria, Silene s.l., Vaccaria) of the subfamily Caryophylloideae. All species were classified a priori as either diurnal, nocturnal, or selfing. Canonical discriminant analysis (CDA) of 13 floral characters revealed significant correlations between floral morphometry and pollination modes. A CDA of taxonomical groups represented with more than three species (Dianthus, and subgroups of Silene s.l.: Lychnis, Silene s.str., and Viscaria), revealed that the discrimination between these four taxa, based on the same floral characters, is also well supported. Main factors for the discrimination of the species with different pollination modes were characters that (a) define nectar accessibility (calyx length, calyx tooth length), (b) are related to the positioning of anthers and stigmatic areas in relation to pollinators and (c) are important for the visual attractiveness of flowers (plate width). The functional distance between the nectar source (anthophore base) and contact zone with pollinators (style tips), given as the sum of anthophore length, ovary length, and style length (hence called AOS-complex) is better correlated with the calyx length than the single characters. Further, the total AOS-complex length differs significantly between pollination modes suggesting that these characters form a functionally linked complex that is related to the pollen placement on, and stigma contact with, the pollinator's body. However, the contribution of anthophore and style length to the total AOS-complex differed significantly between Silene s.l. and other taxa indicating that the taxonomic groups follow different evolutionary ways for the construction of the functionally linked AOS-complex.