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Because pollen sucks.

It does! But if you prefer the smart word: it’s hygroscopic. It attracts water.

And where is water, there is rot.
Which is a problem when you are an insect that relies on pollen to feed its brood and therefore needs to store pollen for weeks, if not months. You may be more or less okay when in a desert or at least able to avoid the rainy season – but in our friendly fertile temperate zones, you’re not.

Still, they are here. Plenty of them. Mason bees and leafcutter bees and carder bees and many more.

Photograph: Neil Bromhall

In their new paper, Christophe Praz and his colleagues suggest a scenario for just how this could have happened:

Before the bees began to feed pollen to their brood (i.e. before they actually became bees) they were something similar to today’s apoid wasps (Grabwespen). They were hunting other insects, paralysed their victims and dragged them into the broodnest where their prey would stay alive for several weeks before being consumed by the larvae.
You may find this disgusting or not, but keeping your food alive until consumption is definitely a good way to keep it fresh.
And there is nothing „primitive“ or old-fashioned about it. There are still plenty of wasps around who do exactly this. But this method does have its costs. Hunting takes time, it’s not without risks, chances to find prey are limited and so on. So when the flowering plants arrived and offered pollen as an alternative source of protein, the bees’ ancestors skipped their carnivorous habits and became all out vegetarians. Which – as we all know – turned out to be a smart move.

But before the flowers and the bees could become one of the biggest success stories on the planet, there was one more innovation needed.

From gene sequencing data and the analysis of diversification rates and biogeography, Praz and his colleagues conclude that for a long time bees had been restricted to arid evironments and that it was only after the „invention“ of traits to impregnate the broodchamber that they were able to achieve their impressive diversity (3900 species today) and worldwide expansion.

They also argue that nest-lining behaviour with foreign material was „invented“ only once within the megachilid bees, some 90 to 100 million years ago (as marked by the green star in the figure below).

[Click picture to enlarge]

So flowering plants and pollen were very important for bees to evolve. But if it hadn’t been for new behavioural traits that allowed to keep the pollen safe from spoilage through water and fungi, the megachilid bees would probably never have been able to leave the deserts.

The cell linings they produce can vary widely. Some bees use mud or chewed leaf paste, others coat the nest with cut out pieces of leaf, and some cement together little pieces of gravel. Whatever the material, all these linings seem to have water-repellent and anti-microbial properties.
There also are a few megachilid species that never got into cell-lining at all.
But they are still in the deserts.

 

Note: This is a slightly modified version of a post I have written in 2011. I decided to re-post it, because I am taking part in this years’ NESCent Blog Contest and I really like the bee-story. With bee populations struggling in so many places, I find it even more fascinating to see where they have come from, and how adaptive nature really is.

 

Litman JR, Danforth BN, Eardley CD, & Praz CJ (2011). Why do leafcutter bees cut leaves? New insights into the early evolution of bees. Proceedings. Biological sciences / The Royal Society PMID: 21490010

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Because pollen sucks.

It does! But if you prefer the smart word: it’s hygroscopic. It attracts water.

And where is water, there is rot.
Which is a problem when you are an insect that relies on pollen to feed its brood and therefore needs to store pollen for weeks, if not months. You may be more or less okay when in a desert or at least able to avoid the rainy season – but in our friendly fertile temperate zones, you’re not.

Still, they are here. Plenty of them. Mason bees and leafcutter bees and carder bees and many more.

ResearchBlogging.org

In their new paper, Christophe Praz and his colleagues suggest a scenario for just how this could have happened:

Before the bees began to feed pollen to their brood (i.e. before they actually became bees) they were something similar to today’s apoid wasps (Grabwespen). They were hunting other insects, paralysed their victims and dragged them into the broodnest where their prey would stay alive for several weeks before being consumed by the larvae.
You may find this disgusting or not, but keeping your food alive until consumption is definitely a good way to keep it fresh.
And there is nothing „primitive“ or old-fashioned about it. There are still plenty of wasps around who do exactly this. But this method does have its costs. Hunting takes time, it’s not without risks, chances to find prey are limited and so on. So when the flowering plants arrived and offered pollen as an alternative source of protein, the bees’ ancestors skipped their carnivorous habits and became all out vegetarians. Which – as we all know – turned out to be a smart move.

But before the flowers and the bees could become one of the biggest success stories on the planet, there was one more innovation needed.

Read more

ResearchBlogging.org
While the honeybees were fine there was little interest in pollinators and pollination in general. People just took it for granted. But with the ongoing news about CCD and concerns about declining bee populations worldwide the interest in wild bees as natural pollinators and “backup” for honeybee pollination has risen sharply. It turned out, however, that very little was known about the changes in diversity and abundance of wild bees, despite their importance for natural and agricultural systems.

In North America, there had been fragmentary observations that populations of wild bees were declining, but the evidence for large scale range reductions has been lacking. Now a study has been published in PNAS that for the first time provides nationwide data for eight historically abundant species of bumble bees. And for some of them, the news is not good.

A team of researchers from the University of Illinois and Utah State University compared historical data of the past 100 years from museum collections with current data based on extensive surveys in the US between 2007 and 2009. They focused on eight target species – four expected to have relatively stable populations, and four where preliminary data suggested a decline. Overall, they had 73 759 specimens in the historical data set and collected 16 788 specimens at 382 sites for the current data set.

From this data, they were, for the first time, able to confirm the decline and to quantify its extent for four species: Bombus occidentalis, B. affinis, B. pensylvanicus, and B. terricola. All these species suffered a reduction in their geographic range as well as in their relative abundance. The species most massively affected is B. affinis, with an estimated reduction in range-area of 87% compared to historical data.

It is interesting to see that the declines in relative abundance appear only in the last 20 to 30 years, with, as the authors point out, “values from current surveys lower than in any decade of the last century”.

Concerning possible causes for the decline, they considered pathogens and genetic diversity in their study.
They consistently found higher infection levels of the microsporidium
Nosema bombi and lower genetic diversity in the declining populations, which makes these factors realistic predictors for the trajectory of a population. But they also state that cause and effect remain still uncertain. From the findings in the current study, it is not yet possible to determine, for example, whether the increased prevalence of N. bombi is the result of higher susceptibility to the pathogen or if N. bombi is simply more common in declining species for other reasons. Factors like habitat fragmentation, the loss of floral and nesting resources, or climate change were not considered in this study.

Cameron, S., Lozier, J., Strange, J., Koch, J., Cordes, N., Solter, L., & Griswold, T. (2011). Patterns of widespread decline in North American bumble bees Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1014743108

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Just quickly: I am so delighted about this new piece of research about how bumble-bees perceive colour patterns, that I don’t want to miss the opportunity to share it.

The study has been conducted by 25 children from Blackawton Elementary School (!) and was published this week in the scientific journal Biology Letters from the UK’s prestigious Royal Society. The graphics are drawn in crayon and the main findings include “We also discovered that science is cool and fun because you get to do stuff that no one has ever done before. “

For more on this, take a look over at Not Exactly Rocket Science, where Ed Yong has a beautiful post about the research and also a lot of background about how the entire project came about.

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As I wrote before, we are trying to get our heads around a few things related to bees and social insects in general. One of them is the concept of the Superorganism (which somehow seems to be much more readily embraced in popular culture than among biologists).

Two prominent proponents of the superorganism-concept are Bert Hölldobler and E.O. Wilson and their book “The Superorganism” is a phantastic source of examples from the natural history of social insects. Although “ant-people” by profession and inclination, they have plenty of stories to tell for “bee-pople” as well.

„[O]ur intention here is to present the rich and diverse natural history facts that illustrate superorganismic traits in insect societies and to trace the evolutionary pathways to the most advanced stages of eusociality.

Our intent in doing so is to revive the superorganism concept, with emphasis on colony-level adaptive traits, such as division of labor and communication. Finally, in presenting the subject this way, we visualize the colony as a self-organized entity and a target of natural selection.

In this book, we view the insect colony as the equivalent of an organism, the unit that must be examined in order to understand the biology of colonial species.“

Hölldobler and Wilson strongly argue that natural selection works on several levels, not just on individuals and their genes, but on groups as well.

„Life is a self-replicating hierarchy of levels. Biology is the study of the levels that compose the hierarchy. No phenomenom at any level can be wholly characterized without incorporating other phenomena that arise at all levels. (…) Natural selection that targets a trait at any of these levels ripples in effect across all the others.“ (pp 7f)

So, while the “selfish gene” does play an important role, they see other mechanims at work as well.
More on the history of the different evolutionary concepts you can find in this interview with Bert Hölldobler on Wired.

Aside from the debate about underlying evolutionary principles, I do like the focus of the superorganism concept on self-organization and decentralized, bottom-up processes. There is no “brain-caste” in insect societies. “Order” and “intelligence” are achieved by cooperation alone. Cooperation according to some very strict and unrelenting rules, though (or behavioral patterns, if that’s a better term).

Also, by the way, Ed Yong reports some compelling Mathematical Support for Insect Colonies as Superorganisms.

Und: “Der Superorganismus” ist inzwischen auch in deutscher Ãœbersetzung verfügbar.

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While the bees have done the smart thing and huddled up for winter, we are wide awake and using the snowy days for catching up on reading and working on the “wider picture”.

There is a lot about bees that is interesting, and the more we study them, the more we keep encountering new and strange and unexpected connections that reach way beyond bees and biology.

Take the superorganism.

Now I know what you are thinking (or what you would be thinking if you were anything like me):

The Borg-Cube

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Canada and the US have about 50 species of native bumblebees. For five of them, a rapid decline has been observed since the 1990s. Three species — Bombus affinis, B. terricola, and B. occidentalis — will now be submitted to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (cf NatureNews: Plight of the bumblebee) (via evolvimus).

Two main reasons for the decline are discussed. One is a fungal pathogen, Nosema bombi, that might have been introduced with commercially used bumblebees from Europe. The other might be climate change, which may cause a shift in flowering times and nectarflow that bumblebees are not adapted to.

Our special friend B. griseocollis still seems to do okay, though :)

Also this month, Anna Morkeski and Anne Averill of the University of Massachussetts published “Wild Bee Status and Evidence for Pathogen ‘Spillover’ with Honey Bees” in the American Bee Journal and in Bee Culture with a very good overview over the current research into bumblebee-decline.

(photo: A. Morkeski)

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Bees navigate by the sun and to be able to do so, they need to measure time (a problem humans were confronted with too, and one that took a lot of time and ingenuity to solve as the arduous History of Longitude shows).
If bees want to fly to the same location in the morning and in the afternoon, they have to know that time has passed in between and correct for the “new” position of the sun. Obviously, they are very well capable of doing this, but the nature of the “bee-clock” had been a mystery to scientists for a long time and it took some significant advances in technology to provide the means to solve it.


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I really didn’t expect this blog to start out quite so frivolous, but here we go. Since we have been talking about bee reproduction quite a bit recently, I couldn’t possibly withhold from you one of the finest examples of how science and entertainment can go together. And of course it is always a pleasure to spend some time with the adorable Isabella Rosselini.

For those who want to know more: here is some of the new science.

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