October 23, 2017

Bees feast on fast food

Honey bees love the invasive plant Himalayan balsam and eat it like ‘fast food’ but, like humans, they thrive better on a varied diet.

A study of honey bee bread in Lancashire and Cumbria bee hives showed that in some samples nearly 90% of the pollen came from the invasive plant Himalayan balsam.

Bee bread is made up of pollen stored in cells in the hive, and is the basic component of food for bee larvae and young bees, while older bees eat nectar in the form of honey.

The study, carried out by scientists at Lancaster University, uses next generation sequencing to analyse 52 samples of bee bread from 26 bee hives to identify which plant species the pollen came from and the nutrient make up of each sample.  Each bee bread sample contained between 6 and 35 distinct pollen species.

Published in the journal Oecologia, the study, shows that the majority of pollen bees collect comes from 16 plant genera, including clover (Trifolium), balsam (Impatiens), blackberry (Rubus), sycamore (Acer) and thistles (Cirsium).

A few samples were almost entirely made up of pollen from Himalayan balsam (Impatiens glandulifera), an invasive plant which has spread fast along English waterways, and which bees love. 

“Himalayan balsam is like fast food for bees, they are obsessed with it and want to chomp it down as fast as possible,” said Dr Philip Donkersley, from the Lancaster Environment Centre, lead author of the study.

“But it may not be the best food for bees, it is better for their health if they have a broad diverse diet.”

Nurse bees in the hives take bee bread from different cells and mix it together to make the best possible brood food for the young bees, just like we might combine ingredients to make a healthy meal for our children, Philip explained.

The researchers analysed how much protein, carbohydrate and other nutrients was present in each sample, to see how closely they aligned with the intake target that bees require with their diet.

“When the food coming back to the hive is dominated by one species, as occurs with the balsam pollen, this limits the number of different food pots the bees can dip into, and makes them less able to mix together the diet they need,” said Philip.

“There have already been studies looking at the nutritional composition of individual plants, we wanted to look at how the composition of the whole plant community impacts on diet and nutrition.

“As protectors of waterways and habitats we need to get rid of himalayan balsam, but it also provides a lot of nectar and pollen for bees. So we cannot only focus on getting rid of it, we also need to think about replacing it with something else, for instance by planting seeds of native riparian (riverside) plants.”

The researchers believe that the results have important implications for people interested in improving the landscape for bees and other wildlife.

“If you want to design a landscape for bees, say in your garden, how do you improve it?

“Rather than just saying such and such a plant provides good nutrition, our findings suggest that diversity and a broad spectrum of plants is best for bees, alongside understanding the importance of some key players such as clover, dandelion and cherry.

“Increasing base level diversity is what matters most, rather than planting specific food for bees.  You can get seed packets of bee friendly plants, but if everyone planted these seeds, you would end up with a comparably less diverse countryside. It’s much less precarious for bees to have 500 different plants than 20, and results in better support for the rest of the environment as well,” Philip concludes.

The study follows on from previous work done by the same team, which showed that honeybees living near areas of extensive farmland were surviving on a lower protein diet than those in hives near natural grasslands and woodlands.

Philip did the research using data collected as part of his PhD at the Lancaster Environment Centre, in association with Newcastle University, with supplementary funding provided by the Waitrose Agronomy Group.

Read the paper in Oecologia: Nutritional composition of honey bee food stores vary with floral composition (Open Access).

Article source/image credit: Lancaster University