Declines in the number of bee species, or diversity, is linked to declines in native wildflower populations. A study published in Science showed a significant decrease in the number of bee species since 1980 in Britain and the Netherlands. The study also concluded a trend towards domination of the pollinator communities of both countries by a smaller number of species.
Small population sizes of certain bee species could be a contributing factor to their extinction. According to one study done by Franzen and Nilsson, the local bee extinction rate was strongly dependent both on local bee population size and habitat quality.
A small population leaves bee species with:
Limited genetic diversity
- Important for influencing ability to adapt to changing environmental pressures or ability to fend off new diseases.
An even smaller effective population size
You’re probably familiar with the beehive. While not all species of bees live in this social arrangement, many do and this affects their breeding habits.
- ONE Queen Beewho lays many eggs, up to 2000 a day!
- Thousands female worker bees that do not breed (instead forage, maintain hive etc)
- Hundreds of male drone bees which fertilize the eggs of the Queen Bee which then develop into more female worker bees
There can be up to forty thousand bees in one hive or colony, but it would have an effective population size of much smaller, because only a fraction of the colony is breeding and passing down their genes to the next generation.
Often male drone bees will drift from hive to hive and mate with different Queen Bees. This improves genetic diversity of the hives but in cases where colonies are few and far between due to habitat fragmentation this becomes less feasible.
Interesting Current Research
Leonard Foster and colleagues at UBC are working to create a genetically modified ‘super bee’ that is resistant to disease and parasitic mites. Learn more about his research here: http://www.ucobserver.org/features/2012/04/honeybee/
 Biesmeijer J. C., Roberts S. P. M., Reemer M., Ohlemuller R., Edwards M., Peeters T., Schaffers A.P., Potts S. G., Kleukers R., Thomas C. D., Settele J. and W. E. Kunin. 2006. Parallel Declines in Pollinators and Insect-Pollinated Plants in Britain and the Netherlands. Science. 313: 351-354.
 Franzen M. and Nilsson S. G. 2010. Both population size and patch quality affect local extinctions and colonizations. Proceedings of the Royal Society of Biological Sciences. 277: 79-85.