Experimental manipulation of floral scent bouquets restructures flower–visitor interactions in the field

Abstract

Summary 1.A common structural feature of natural communities is the non-random distribution of pairwise interactions between organisms of different trophic levels. For plant-animal interactions, it is predicted that both stochastic processes and functional plant traits that facilitate or prevent interactions are responsible for these patterns. 2. However, unbiased manipulative field experiments that rigorously test the effects of individual traits on community structure are lacking. We address this gap by manipulating floral scent bouquets in the field. 3. Manipulation of floral scent bouquets led to quantitative as well as qualitative restructuring of flower-visitor networks, making them more generalized. Olfactometer trials confirmed both positive and negative responses to scent bouquets. 4. Our results clearly show that the distribution of insect visitors to the two abundant study plant species reflects the insects' species-specific preferences for floral scents, rather than for visual or morphological floral traits. 5. Thus, floral scents may be of major importance in partitioning flower-visitor interactions. Integrating experimental manipulations of plant traits with field observations of interaction patterns thus represents a promising approach for revealing the processes that structure species assemblages in natural communities.

Elevation predicts the functional composition of alpine plant communities based on vegetative traits, but not based on floral traits

“…Following this finding, the large within and relatively low between community variation in floral traits 1 3 suggest that these traits respond to different factors than vegetative traits. Accordingly, the flowers' morphology, colour, and scent emission are well known to mediate interactions with pollinators Kuppler et al 2016;Larue et al 2016), as they either facilitate interactions by means of attractive traits and the provisioning of resources or decrease or prevent interactions by means of morphological barriers, inconspicuous appearances, or repellent scents (Junker 2016;Junker and Parachnowitsch 2015;Katzenberger et al 2013;Papiorek et al 2015;Stang et al 2007). According to the importance of functional flower traits in determining the visitor spectrum of a plant species, it has been shown that a high functional diversity in floral traits supports high species richness in flower visitors Potts et al 2004).…”

“…The traits considered have been chosen based on their importance for physiological processes and adaption to environmental conditions (Stubbs and Wilson 2004) or their important function in shaping plant-pollinator interactions Junker and Parachnowitsch 2015;Larue et al 2016). Per plant species and per plot, we recorded n = 7 vegetative traits and n = 6 floral traits.…”

“…Floral volatiles were collected from all plant species per plot using dynamic headspace sampling methods directly in the field (Larue et al 2016). Flowers were enclosed into scentless polyethylene tetraphthalate (PET) oven bags (Toppits ® Cofresco Fischhalteprodukte GmbH & Co. KG, Minden, Germany) for 45 min, and afterward, the enriched headspace was sampled for 2 min into volatile traps with a flow rate of 200 ml min −1 .…”

“…The few studies that considered floral traits in a community-ecological context (e.g., Benadi et al 2014;Junker et al 2013;Runquist et al 2016;Wolowski et al 2017) suggest a contribution of these traits to plant community composition (Benadi 2015;Pauw 2013;Sargent and Ackerly 2007). Indeed, recent studies show that floral traits, such as morphology, colour, and scent shape plant-pollinator interactions, affect the diversity of flower visiting animals in communities, and explain the presence or absence of competition between plant species for pollinators (Carvalheiro et al 2014;Junker et al 2013Junker et al , 2015Junker and Parachnowitsch 2015;Kuppler et al 2016;Larue et al 2016). Thus, pollination and floral traits are directly linked to plant reproduction and fitness, which are fundamental processes related to biomass gain and species diversity in communities.…”

The smell of environmental change: Using floral scent to explain shifts in pollinator attraction

“…The majority of studies on floral VOCs, especially early investigations, aimed only to catalog the VOCs produced and not the functional consequences of those VOCs for pollinator foraging (Raguso, 2008a). Recent studies have shown that the combinations of VOCs presented by plants via their flowers—not surprisingly—send signals to pollinators and influence plant–pollinator interactions (e.g., Suchet et al, 2011; Farré-Armengol et al, 2015; Larue et al, 2016). Floral VOCs can vary diurnally (e.g., Loughrin et al, 1990; Majetic et al, 2007), spatially among populations (e.g., Majetic et al, 2008), spatially across environmental conditions and geographic ranges (e.g., Majetic et al, 2009a;Soler et al, 2011), with floral genders (e.g., Ashman et al, 2005; Ashman, 2009), and with floral color (e.g., Odell et al, 1999).…”