Bee populations decline along with their preferred flowers for pollination, according to a new finding, examining bees collected decades ago.

Colony collapse disorder is the name given to unexplained mass deaths of bees each winter, leading to heavy loses of bee populations in North America and Europe. Although colonies typically lose a significant number of their members each winter, the number of deaths has risen significantly over the last couple of decades. An additional threat to the insects has also been identified.

A lack of biodiversity could also be responsible for mass losses, according to a group of researchers from Oregon State University. The group studied pollen collected off wild bees, collected from 57 different species. The material was collected before 1950, and stored at museums located around the Netherlands. Researchers discovered different species of bees pollinated favored plants, and as the varieties of vegetation died off, so did the insects. Investigators believe challenges posed by declining food sources for bees are responsible for most of the recent mass deaths. The size of bees also made a difference in determining survivability for the insects, as smaller bees require less pollen to survive than their larger brethren.

"Strategies to mitigate bee losses may need to target the specific host plants of declining bee species," Jeroen Scheper, from the Alterra Research Institute in Holland, said.

By re-planting chosen plants of bees, Scheper believes it may be possible to assist bee populations recovering from recent devastating colony loses. Bee loses due to reductions in biodiversity can compound problems presented by colony collapse disorder. That phenomenon, which many people blame on pesticides and pollution, has led to the loss of up to 90 percent of bees in some areas of North America and Europe.

Carrying out studies linking specific bees to certain flower species has been challenging. Bee varieties that have disappeared were never tested to determine their preferred flowers, and it is now too late to carry out these tests. Examination of insects from decades in the past allowed researchers to determine where the insects obtained the pollen, utilized for minerals and protein. The insects utilize nectar to supply energy.

Bees pollinate between 70 and 80 percent of the food crops, making it possible for the plants to reproduce.

The White House has ordered that many federal buildings plant flowers beneficial to bees and other pollinators. Similar plants will also be placed along highways, in an effort to benefit the insects, essential for crop production.

Declining bee populations and their relation to the loss of biodiversity in plant species was detailed in the Proceedings of the National Academy of Sciences (PNAS).

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