Biodiversity – samesame, but different
Bees are excellent examples for the importance of biodiversity. Worldwide, there are more than 20,000 species. Each of these species is different and has its own way of living, but also some common traits. As I heard often in Thailand: samesame, but different. The differences are most stunning. Bees look different, they behave different, like different flowers… but let’s begin with defining what we are talking about.
What makes a bee?
If so many species are bees and they have so many differences, how can we decide that insect is a bee? This is because all of them have common traits. It is not pollination itself (also wasps, flies, beetles and others pollinate flowers) but their specialization on it. They are vegetarians, feed on pollen and nectar instead of adding some animal protein like their closest relatives. This specialization of feeding on flowers led to a variety of behavioural and anatomical features to exploit this resource most effectively. For example many bees are hairy, and these hairs are plume-like to make it easier to carry the pollen. The mouthparts of bees are also adapted to feed on nectar.
The ancestors of today’s bees were wasps, in older German literature you can still find the term “flower wasps” for bees. Bees evolved together with flowering plants. During this process, the flowers got more diverse and “began” offering rewards like nectar and giving signs where they are. Bees on their side diversified, too: they divided into short-tongued and long-tongued bees, some species specialized on certain flowers, social species evolved. You can find a summary of bee evolution (which would be a post of its own) here.
Diversity hotspots in Mediterranean areas
Often, biodiversity hotspots (i.e. areas where a large number species of a certain group live) are in the tropics. For bees this is not true, quite the contrary: tropical areas are “bee-lite” zones. In these areas, plants with flowers that are suitable for bees are not very common. Therefore, not many bee species live in the tropics and pollination is done also by other insects, birds or bats.
Hotspots for bee diversity are areas with Mediterranean climate. Here the right flowers grow and we find the largest variety of bee species. In Europe, for instance, Spain has 1110 bee species, Italy 969 or Greece 935. On the other hand, in the UK there are 264 species, in Sweden 298 and in Germany 575. Other regions in the world with Mediterranean climate are California, North-Central Chile, Central Asia, South Africa and Southern Australia.
But even not living in one of these hotspots, you can find a lot of interesting bees. I wish I would have seen all different species in Germany. They are already so diverse, that in the field I often just address them with their genus name: “Oh, look, there is a Lasioglossum.”. In Italy, I very often do not dare to say even this. I stay with the family instead. Here come some of the species I dare to address by name:
Flight period and nesting habits
As you can see, these bees look quite different. They are also examples for the very diverse biology bees have. All three of them are solitary, each female builds its own nest and lays eggs. This solitary way of life is quite usual for bees, social species are a minority. But here are some differences between the three species on the photos, beyond their looks:
Anthidium manicatum, the Wool Carder Bee, is a summer bee, you can see them in July-August. This may be one of the few bee species the male is more eye-catching as the females: the hover around attractive flowers and defend them from any other bee around, except females of their species. They have spines at the end of their abdomen, and when they attack other bee species, they can can even hurt them. Look after them when you see flowers with hairy leaves: the females use these hairs as nesting material (I have no photo, I’m sorry…). Sometimes they even nest in trapnests.
Osmia cornuta on the other hand is a spring bee, and a very early one: you can observe them in March-May. Usually they start flying before the Red Mason Bee comes out. I live in a region where both species exist, they are very frequent in trap nests. I hope that this year I will have some of these on my terrace… They are not very picky where to nest and also feed on a big variety of plants.
This is different for the third species: Andrena vaga, a mining bee specialized on willow pollen. They fly at the same time as O. cornuta, but as you can see nest in the ground. Most bees do. They dig long “tunnels” with brood cells at the end and provide them with pollen, sufficient for the larva to feed on it, lay an egg and close the nest. Their offspring will never know its mom, as they hatch only in the next spring.
Bee diversity in series
These are only small glimpses on the biodiversity of bees. As spring is coming and I cannot wait to seem them again, I wanted to do a small series on bee diversity and why it matters. Every Friday in March, I will post about it. Next week, there will be an introduction to the most common bees you can find in your garden. The third week, I will address the downsides of biodiversity, the introduced or alien species. Not every diversity increase is positive. And finally, end of March, we will talk about how to help bees. Will you join me on this journey?