Flowering phenology and pollen-to-ovule ratio in coastal dune communities near Eurosiberian-Mediterranean border in the NW Iberian peninsula

Pollen-to-ovule ratios and flowering phenology were studied in 15 of the most important entomophilous species of the coastal dunes of the northwest Iberian Peninsula, located bioclimatically in the Cantabro-Atlantic territory but with significant Mediterranean influence. Specifically, we aimed to answer the following questions: 1) Does P/O ratio show any consistent pattern in entomophilous dune species? 2) Does flowering phenology differ in any consistent manner between the outer active-dune habitat and the inner fixed-dune habitat? 3) Do intra- or interspecific flowering overlap differ between active dunes and fixed dunes? 4) Does flowering phenology accord with that observed in Eurosiberian or Mediterranean territories? P/O ratios were in all cases within the range reported for xenogamy. In general, active-dune species flowered later than fixed-dune species and showed lower and more variable intraspecific flowering overlaps. The Mediterranean influence is particularly marked in the fixed dune, in which the peak flowering periods mostly occur somewhat earlier than in the active dune.