Yearly fluctuations of flower landscape in a Mediterranean scrubland: Consequences for floral resource availability

Abstract

Species flower production and flowering phenology vary from year to year due to extrinsic factors. Inter-annual variability in flowering patterns may have important consequences for attractiveness to pollinators, and ultimately, plant reproductive output. To understand the consequences of flowering pattern variability, a community approach is necessary because pollinator flower choice is highly dependent on flower context. Our objectives were: 1) To quantify yearly variability in flower density and phenology; 2) To evaluate whether changes in flowering patterns result in significant changes in pollen/nectar composition. We monitored weekly flowering patterns in a Mediterranean scrubland community (23 species) over 8 years. Floral resource availability was estimated based on field measures of pollen and nectar production per flower. We analysed inter-annual variation in flowering phenology (duration and date of peak bloom) and flower production, and inter-annual and monthly variability in flower, pollen and nectar species composition. We also investigated potential phylogenetic effects on inter-annual variability of flowering patterns. We found dramatic variation in yearly flower production both at the species and community levels. There was also substantial variation in flowering phenology. Importantly, yearly fluctuations were far from synchronous across species, and resulted in significant changes in floral resources availability and composition at the community level. Changes were especially pronounced late in the season, at a time when flowers are scarce and pollinator visitation rates are particularly high. We discuss the consequences of our findings for pollinator visitation and plant reproductive success in the current scenario of climate change.

Spatial variability in a plant–pollinator community across a continuous habitat: high heterogeneity in the face of apparent uniformity

“…At that time, flower visitation rates are low compared to late spring, when floral resources sharply decline and a greater number of pollinator species are active (Bosch et al 2009, Filella et al 2013. Therefore, floral resources are more likely to become limiting as the season progresses (Flo et al 2018). A previous study in the same area encompassing the entire flowering season found evidence of displacement of wild pollinator communities (especially large bees) by honey bees (Torné-Noguera et al 2016).…”

“…Because as much as 99.1% of honey bee visits were on R. officinalis and T. vulgaris, it is unlikely that honey bees could have any competitive effects on pollinators visiting other, less abundant, flower species. This result may be related to the time of the year (early spring) in which surveys were conducted, corresponding to the peak of flower production in the park (Flo et al 2018). At that time, flower visitation rates are low compared to late spring, when floral resources sharply decline and a greater number of pollinator species are active (Bosch et al 2009, Filella et al 2013.…”

“…We surveyed 2-4 plots per day between 2 and 17 April 2015. This period corresponds to the flowering peak of the scrubland community (Flo et al 2018). The field team was composed of eight people trained to identify the pollinator fauna of the study area.…”

Pollinator‐mediated mechanisms for increased reproductive success in early flowering plants

“…In the tallgrass prairie community, Echinacea tends to flower mid-season. However, there can be high year-to-year variation in the pattern and abundance of co-flowering species (Flo et al 2018). In addition, as the flowering season progresses, the proportion of Echinacea heads that have finished shedding pollen increases.…”

Seasonal dynamics in a cavity-nesting bee-wasp community: Shifts in composition, functional diversity and host-parasitoid network structure

“…It also shows seasonality in the availability of food resources for cavity-nesting bees (pollen and nectar) and wasps (insect and spider prey). Pollen and nectar are much more abundant in spring [ 31 , 32 ], whereas arthropod preys (aphids, caterpillars and spiders) are more abundant in summer [ 33 – 36 ]. For these reasons, and given that solitary bees and wasps usually have short activity periods [ 37 – 39 ], we expect high species and functional trait turnover across seasons.…”