In this new post, Natasha de Manincor from University of Lille presents her work “Geographical variation of floral scents in generalist entomophilous species with variable pollinator communities”. She highlights the importance of Volatile Organic Compounds for pollination, discusses the mechanisms behind plant intraspecific chemicals variability and shares her passion for fieldwork all over the world.
About the paper
Plants are limited by their immobility, so they need to invest in a suite of floral signals to attract diverse and efficient pollinator species to reproduce. Floral traits such as nectar production or flower colour or scent, as well as their quantity and quality, are crucial to attract pollinators. One floral signal that recently gained more attention is floral scent (assessed through composition in Volatile Organic Compounds, VOCs), a complex mix of several compounds which are produced by biochemical pathways of secondary metabolism. VOCs are considered as major non-visual attractants for many pollinator species and they have been shown to vary because of genetic variation between populations or in response to environmental variation (such as light, temperature or type of soil), i.e. phenotypic plasticity. Differences in environmental conditions can also influence pollinator occurrences and abundances, which begs the question of whether variation in pollinator communities can drive changes in the emission of volatile compounds, independently of variation in environmental conditions. In other words, what happens when the same plant species is present in different locations with potentially different pollinator communities? How do floral scents vary within and among regions? How do floral scents co-vary with pollinator communities or, conversely, will two plant species share more pollinators if they have more similar scents? Finally, does phenotypic plasticity alone explain the variation in floral scents detected in the field (i.e. does such variation not persist when investigated in a common garden experiment)? So many questions and so little time, but this is what we tried to figure out.
In our study we focused on four generalist plant species which were present in different regions and at different latitudes, along an environmental and diversity gradient in France. In six calcareous grasslands we collected VOCs emission and we recorded pollinator visits to document geographical variation of pollinator communities associated to each plant species. Studies that focus on natural conditions commonly explain variation as the result of local adaptation to pollinators, often excluding phenotypic plasticity. To look for signs of phenotypic plasticity, after collecting seeds from natural populations, we compared the VOCs sampled in the field with the VOCs emitted by the same species reared under the same greenhouse conditions. Only the comparison between natural populations and controlled conditions can help ascertain the origin of the variation.
Our results showed a clear difference in floral scents both among species and among populations of the same species, with a high correlation between floral scents variation and pollinator variation since the presence of some pollinators was associated to the production of specific compounds. However, with the greenhouse study we found evidence of local genetic adaptation in only one of the four species, while for the others the geographic variation observed in the field could be attributed to an effect of phenotypic plasticity.
About the research
One of the strengths of this study is that we focused on plant species with generalist pollination, i.e. that are visited by widely different pollinator species, which is not the norm for this type of research on volatile compounds. Very few studies have attempted to link the pollinator community visiting plants involved in a generalized pollination system, and even fewer have simultaneously compared floral scents among multiple species and populations in relation to these communities. Moreover, based on comparisons between field and greenhouse conditions, we also were able to answer an important question behind the mechanism of floral scent variation, which is not often investigated. Overall, our findings suggested that genetically based variation and phenotypic plasticity might both contribute to observed intraspecific variation in floral scent. Our study is a first step in the understanding of how geographical variation of floral scents in plant species with generalist pollination can occur and it constitutes a potential important addition to our knowledge on this topic.
This research was conducted during my PhD at the University of Lille (France), in the EEP Laboratory. My doctoral work was part of a larger collaborative project that included different laboratories and research groups, financed by the ANR (Agence Nationale de la Recherche, https://anr.fr/Projet-ANR-14-CE02-0012). The general aim of my PhD was to study plant-pollinator network variation along a latitudinal gradient in France. For this work we focused on the variation of species traits within and among populations, and we choose to use floral scents since they are less studied compared to other floral traits.
About the author
I have always been fascinated by nature and I always loved travelling, and these two things combined helped me discover and build my passion about ecology. I got involved in ecology during my bachelor’s degree in Biology at the University of Bologna (Italy) where, as part of an internship, I studied the pollinators – mainly wild bees – of an endangered plant species. After that, I moved in different countries and environments where I got involved in different ecological projects, from the desert to the bushland in Australia, to the calcareous grasslands in France and now to another desert in California (USA). For my PhD, I had the amazing opportunity to travel around different regions and collect data to build plant-pollinator networks to study how they change in space and time. I spent a huge amount of time in the field, which I think is the most amazing part of being an ecologist, and I hope to keep doing it in the future. However, it can also be very hard and a long process, especially to collect a suitable amount of data to show how species interact with each other and how and which measure they can be impacted by global changes. I am currently a postdoc in the Rafferty Lab, at the University of California, Riverside (UCR). As part of my postdoctoral research, I am investigating how climate change, and in particular global warming, can affect plant-pollinator phenologies, interactions and traits using a multi-generational approach. I am also continuing to do fieldwork recording plant-pollinator interactions across an altitudinal gradient, because…why not?
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