Flowering overlap in Mediterranean plant communities along an ecological succession with recurrent mowing - Synchrony predominates at earlier stages and under mowing

International audienceIntroduction Flowering phenology is critical for the success of plant reproduction and depends both on abiotic constraints and on biotic interactions with other plants and fauna. Flowering synchrony or asynchrony within communities could thereby reflect local assembly processes associated with reproductive strategy. Changes in flowering phenology along the succession has been little studied. Thus, the interplay of a recurrent disturbance on successional changes in reproductive strategy remains unknown. Road slopes that are yearly mown are a good model to study these effects. Questions How do changing community assembly processes along the succession and due to mowing influence flowering overlap (i.e. synchrony or asynchrony) ? Does flowering overlap depend on pollination strategies and flower colour diversity in communities? Results Decrease of flowering overlap along the succession. Slower successional decrease with mowing. Greater flowering overlap than expected (flowering synchrony) before 30 years without mowing. Longer flowering synchrony with mowing (until 40 years). Higher overlap with lower colour diversity. Lower overlap on North-oriented than on East-oriented slopes. Decrease of overlap with increasing slope angle Lower flowering overlap for strictly entomophilous species than for other species. Significant relationship of flowering overlap with SLA and LDMC at community-level (CWM). Discussion In earliest successional stages, acquisitive plants highly depend on favorable meteorological conditions for vegetative growth and following investment in reproduction, thus resulting in higher flowering synchrony. Assembly appears neutral in regard to flowering phenology in later stages, probably reflecting a lower influence of constraints impeding flowering synchrony for conservative plants. Mowing increases flowering synchrony probably due to a synchronization of vegetative growth and via its influence on resource-use strategy. Flowering synchrony seems related to facilitation for pollinators’ attraction with enhanced colour signal (lower flower colour diversity ), for entomophilous species in particular. Conclusion Reproductive timing is an important driver of community assembly and appears tightly related to resource-use strategy. Flower synchrony within communities can reflect both influence of abiotic conditions constraining the optimal period to invest in reproduction in Mediterranean area facilitation processes helping entomophilous species to attract pollinators more efficiently thanks to synchronous homogenously-coloured flowering signal