Pollen library

Pollen library

Uncovering potential ecological interactions between local host flowering plants and their associated wild bee pollinators

Small plant particles

Pollen grains are small plant particles that can vary greatly in size, shape, colour and chemical composition. They are only made by seed-producing plants, either in the Stamen (in the case of angiosperm plants) or within the male cones (in the case of gymnosperm plants).
The function of pollen grains is to carry the male reproductive cells that contain key genetic information for plant sexual reproduction.

Phenomenal

Due to its high nutritional value, pollen grains are an important food source for various animal groups, including birds, reptiles, mammals, insects and other invertebrates.

Without pollen grains, seed and fruit formation are just not possible.

Pollen can travel very long distances, carried either by the wind, water or animals, especially insects. In fact, it is a major evolutionary novelty that has allowed flowering plants to inhabit all continents, facilitating the colonisation of diverse terrestrial environments and promoting plant biodiversity.

Pollination occurs when pollen grains reach the receptive surface of the female reproductive system of a compatible plant (stigma), triggering a process that will result in the combination of male reproductive cells (inside the pollen) and female reproductive cells (inside the ovary of the plant).
Flowering plants have a wide variety of strategies to ensure that their pollen is dispersed and reaches a suitable partner, many of which involve using various animal vectors. Most commonly, plants have a cooperative relationship with the animals they use as vehicles for pollination. The plant depends on the animal-vector for pollen transport and the animal-vector depends on their host plant for nourishment, breeding spots or shelter.

Due to its high nutritional value, pollen grains are an important food source for various animal groups, including birds, reptiles, mammals, insects and other invertebrates. Many plants produce copious amounts of pollen to increase their chances of reaching a receptive partner, attracting “palynivore” animals in the process. Moreover, plants can also produce nutritious secretions that serve as additional rewards for potential visitors (e.g. nectar and floral oils). Typically, when an animal-vector feeds on a flower, some pollen grains adhere to various parts of its body and are taken to any location the animal visits after finishing its meal. If the animal feeds again on a compatible flower, some of this pollen may rub off on the female parts of a receptive plant, allowing fertilisation and seed formation. This type of insect-mediated pollination is called “Entomophily”.
Because of the numerous actors involved in this process, the study of entomophily (a.k.a anthecology) is an interdisciplinary field that combines knowledge from several branches of biology, such as botany, entomology and ecology.

The majority of wild animal pollinators are insects. The ideal type of pollinating insect is hairy (so that pollen sticks to its body), and spends plenty of time exploring the flower, thus increasing the chances of coming into contact with the reproductive structures of the plant.
Wild bees rely heavily on flowers for nourishment and have special adaptations (both structural and behavioural) to maximize pollen gathering, making them highly efficient pollinators. Flowering plants provide wild bees with a reliable source of sugar (nectar) and protein (pollen), the latter being used as the primary larval food for their brood. Adult females actively collect pollen, most commonly using specialised brushes of body hair (scopae or corbicular structures), arranging the grains into compact loads to facilitate their transport to their nests. A single female may need to gather the pollen of hundreds of flowers to provide enough food for a single offspring, visiting the host plants several times a day. As a consequence of their parental care, they visit more flowers than the amount needed to just maintain themselves, increasing the chances of pollen grains to reach a compatible plant. Depending on the structure of the flower, wild bees can also adopt various strategic, unconventional behaviors to remove pollen (e.g. buzz pollination behavior), gaining access to plants not available to other insect groups and contributing to their reproduction. Moreover, since wild bee males also forage for nectar and are often hairy, they provide pollination services through passive pollen accumulation.
Some of the ecological interactions established among wild bees and their plant hosts are very specific, having been shaped by coevolution between both groups over millions of years. Therefore, understanding the intricate link between wild bees and their host plants is crucial to ensure effective conservation strategies for both groups of organisms. However, we still know little about the ecology and impact of wild bee biodiversity decline on the complex network of ecological interactions they form part of. In addition, our understanding of the situation is hampered by the fact that several wild bee species dwelling in Luxembourg are currently classified as “Data Deficient”.

“Without pollen grains, seed and fruit formation are just not possible.”

“Without pollen grains, seed and fruit formation are just not possible.”

Pollen can travel very long distances, carried either by the wind, water or animals, especially insects.

Beelibre’s pollen repository

A First for Luxembourg

To support research on ecological interactions between local flowering plants and their wild bee pollinators, the Beelibre project has established Luxembourg’s first national pollen repository. This initiative aims to enhance understanding of plant-pollinator relationships and contribute to ongoing conservation efforts.

Samples Collection

Between 2023 and 2024, the Beelibre project collected over 600 pollen loads directly from the scopae of foraging female wild bees. Using cotton swabs, pollen was carefully extracted from bees found in the field, ensuring a non-invasive collection method that preserves both the pollinators and their environment.

Storage and Preservation

Each pollen sample, collected from identified and photographed wild bees, was stored in Eppendorf tubes filled with 96% ethanol. To maintain their integrity, all samples are currently kept at -20°C in the scientific annex of the Musée national d’histoire naturelle de Luxembourg.

Availability

The pollen repository is accessible for scientific research upon request. This collection offers a valuable resource for researchers studying pollination biology, biodiversity, and the ecological roles of wild bees within Luxembourg’s ecosystems.

Data sharing

The Beelibre pollen collection will be made available as an online catalogue via the developing DiSSCo RI (www.dissco.eu), where the Musée national d’histoire naturelle de Luxembourg serves as the national node. This digital platform will facilitate data sharing and collaboration among researchers worldwide.

Applications

The repository’s data and samples can support diverse scientific fields, including taxonomy, evolutionary biology, genetics, forensic science, agriculture, climate change studies, and even human health research. By providing access to these samples, Beelibre contributes to a wide range of interdisciplinary research opportunities.

Pollen sampling and storage.

1. Foraging female

1. Foraging female

2. Pollen extraction

2. Pollen extraction

3. Collected sample

3. Collected sample

4. Long-term storage

Looking for available pollen samples ?

Looking for available pollen samples ?

First, go to the species profile of your wild bee of interest. On the species description, look for this flower icon. That means there are pollen samples available for this species.


Afterward, you can contact us to get more details on the specific information of these samples.

References

Dar, S. A., Hassan, G. I., Padder, B. A., Wani, A. R., & Parey, S. H. (2017). Pollination and evolution of plant and insect interaction. Journal of Pharmacognosy and Phytochemistry, 6(3), 304-311.

McCormick, S. (2013). Pollen. Current Biology, 23(22), R988-R990.

Thorp, R. W. (2000). The collection of pollen by bees. Pollen and pollination, 211-223.