Inside the feeding behavior of a pollinivore

Laura Bellec, Gaëtan Seimandi-Corda, Kathleen Menacer,Marie Trabalon, Jérôme Ollivier, Christophe Lunel, Sébastien Faure, Anne-Marie Cortesero,Maxime Hervé

This is a plain language summary of a Functional Ecology research article which is published here.

Animals need to find food to survive and grow but searching for food is energetically expensive. Thus, animals have evolved strategies that allow them to maximize food intake per unit of time. These so-called ‘foraging strategies’ depend on various characteristics of the food such as its accessibility, its nutritional quality and the toxins it contains. Therefore, researchers face the question: How can we know which food characteristics drive the foraging behavior of a given animal?

In this study, we tried to decipher the characteristics that influence the feeding behavior of a small pollinivorous beetle called… the pollen beetle. We did that at a very small scale, namely the inflorescence of a rapeseed plant. Before flowering, when the flower buds are still closed, the pollen beetle pierces the bud wall, called the perianth, to reach the pollen inside the bud. It was already known that pollen beetles prefer to feed from the youngest buds, i.e. the smallest ones, but what explains this preference?

(Left)  “Rapeseed pollen beetles” by Gilles San Martin is licensed under CC BY-SA 2.0
(Right) “OSR Pollen Beetle 21” by CropShot is licensed under CC BY-SA 2.0

Since pollen beetles feed from open flowers for the rest of the year, we used the preference for flowers over flower buds to answer this question. From a series of lab experiments on plant organs and artificial substrates, we found that the preference for flowers was related to the direct access to the pollen and its higher nutritional quality. We next tested whether these two characteristics could explain the preference for young buds over older ones when flowers are still closed. To do so, we used a mathematical model to predict how much pollen beetles should favor young buds, given the time needed to pierce the perianth and access the pollen, and the nutritional quality of the pollen. We found that young buds are more profitable than older ones, i.e. they allow maximizing nutrient intake per unit of time even though they contain less pollen than older buds. Moreover, simulations showed that how much young buds should be preferred fitted very well with the actual preference of pollen beetles. It is then likely that the foraging strategy of pollen beetles on flower buds aims at maximizing nutrient intake per unit of time.

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