Similar reproductive success of the two petal colour polymorphisms of Cistus ladanifer (Cistaceae)

Abstract

Variation in flower colour can reflect adaptive responses to selective pressures generated by pollinators. Cistus ladanifer is a Mediterranean shrub that displays self-incompatibility, entomophyly and polymorphism for the presence of a dark coloured blotch in the base of their petals (var. maculatus with blotched petals and var. ladanifer with unblotched petals). In order to investigate the effect of the petal blotch and geography in C. ladanifer reproductive success, variation in female reproductive output (flower production, fruit set, seed set) was analysed in four and three Iberian populations of var. ladanifer and var. maculatus, respectively. Additionally, we tested whether co-existence of these two C. ladanifer phenotypes yielded different reproductive output (ovule production, seed set) in a subset of two populations. Significant differences in flower production (56.4–229.4%), fruit set (64.9–93.8%) and seed set (82.8–98.0%) among populations were reported. Geographical and taxonomic variables did not significantly explain this variation. Significant results between floral morphs within a single population were found neither for ovule nor for seed production. Our findings suggest that the petal blotch in C. ladanifer should be considered to be neutral in its effect on fruit and seed production and its occurrence may simply reflect a relaxed selection under current conditions.