Number of cases campus Landau: 1 (warning level Gelb until 16.04.2021) Action plan

Reproductive ecology of euglossine-pollinated plants

Reproductive ecology of euglossine-pollinated plants

Plants in tropical understory forest communities show an increased degree of specialization in their pollination biology. Due to the high diversity of tropical environments and the accompanying scarcity of conspecific plants, specialization appears to be an important achievement to guarantee successful cross-pollination.

We are studying the mechanisms of how tropical understory plants have attained to restrict their pollinator spectrum, how they establish reproductive isolation from sympatrically occurring relatives and how new plant species might originate. Our study organisms are plants pollinated by euglossine bees (Hymenoptera: Apidae: Euglossini), which are also known as “orchid-bees”. Euglossine bees are only found in the Neotropics and possess two unique characteristics: a very long proboscis and the volatile collecting behaviour of the males. Several genera of Neotropical plant families have specialized on the pollination by euglossine bees. These are either plants with perfume – offering flowers (usually no nectar or fodder-pollen is produced) or plants with long-tubed nectar-flowers or (mostly) buzz-pollinated pollen-offering flowers.  
 

Perfume- offering flowers

Perfume-offering flowers

The pollination biology of the perfume-flowered plants is especially interesting because the spectrum of volatile substances each bee species collects is species-specific. Therefore, the scent mixture a flower produces determinates the attracted bee species. This means that closely related plant species may occur in the same area and flower at the same time without producing hybrids just by having different floral scents. In other words: floral perfume serves as an isolation factor! In our investigations, we study the chemical composition of floral perfumes, their variability and the effect on the pollinator spectrum. Since modifications of the scent lead to the attraction of different bee species, on a large scale this development could result in the origin of new species. This might also be the reason why most euglossine-pollinated plants belong to species-rich genera.

 

Nectar- and pollen-offering flowers

Nectar- and pollen-offering flowers

In contrast to the perfume-flowered species, the reproductive biology of euglossine nectar and pollen hosts is fairly unknown. Observations show that many of these plants are almost exclusively visited by euglossine bees and that sympatrically occurring plant species often have different pollinators. But what is the reason for this? We study floral characteristics, like morphology, nectar composition, perfume composition, and flowering phenology of euglossine-pollinated plant communities and try to find correlations to the visitor spectra in order to solve this puzzle.