(Be)evolution – Where social insects come from

With veganism and vegetarianism trending in Berlin like a rampant wildfire spreads in the grasslands of the Australian outback in summer time, I´ve heard: “Humans will eventually evolve into herbivores” more times than I care to count. Though I personally am trying to live the vegetarian lifestyle (though admittedly not very strictly, because I do it for environmental rather than animal rights reasons), I believe that being an omnivore is what helped us get to where we are at the present. Evolving towards a diet based solely on plant – derived food? Who does that?

Bees did, it turns out. Before they decided to chow down exclusively on all those sweet things a flower has to offer, they were flying around the mid – Cretaceous jungle as hunting wasps in search of some proper meat. Nectar and pollen were still left to be discovered, but once the wasps realized how much easier it was to specialize on pollenivory instead of carnivory – possibly they were doing it for animal rights and environmental issues as well – some of them went for it and never looked back, quickly adapting and evolving to the animals we find pollinating our flowers in our gardens today.

In 2006 an amber fossil was found in Burma containing a creature, that – if I had found the thing trapped inside – I would have described as a squashed winged ant, that despite its mushed – up features, was caught up in an eternal struggle to flip back onto its feet. Legs in the air, a crushed wing on the side, covered by solidified, honey-colored tree sap, this critter looks like it´s definitely missing parts, but not like a missing link between anything to the untrained eye. Yet, scientists from the Cornell Labs – due to their work in the ornithological field, the bird-lover in me has a bit of a scientific crush on that institute – were able to identify the little bugger as a male bee with many wasp-like features. The pattern of veins on the forewings resembles the pattern in small bees, whereas most parts of the legs and spikes found protruding from various segments look very much like they do on wasps today. Interestingly, a couple of pollen grains can be found on the hairs of the antennal cleaner, hinting at the food source of this ancient bee-like wasp.

This fossil is a beautiful example of a transitional fossil, which in human evolution is referred to as a “missing link”. Keep in mind, that the term “missing link” is used only by journalists and if you want to be taken seriously by biologists, you should refrain from a) asking to see one only to ignore their invitation to the local natural history museum (“But doesn´t the “missing” mean you´re still looking for it?!” and b) referring to transitional fossils as missing. Once you´re in the museum and take a good look at the, for example, marvelous transitional fossil of the Archaeopteryx – the Berlin museum has purchased the original and it sent a shiver down my spine to see it with my own eyes about a year ago – and you will see the distinctive display of transitional anatomical traits from ancestor (dinosaur, or in our case: wasp) and descendant (bird, or for our purposes: bee) species.

But this is not the only reason the publication made it into the prestigious journal “Science”. What made this find so exciting was its age. The bee was trapped in tree sap 100 million years ago, making it the oldest bee fossil ever found, predating every other bee fossil that had ever been found by 35 – 45 million years! This discovery, combined with a molecular and morphological study done by the same lab group, completely upturned our knowledge on the evolution of the bee. Not only were they older than previously believed, but could be shown to originate not from the Southern Hemisphere, but from Africa. The fossil age overlaps nicely with the time flowers started to diversify, for which bees have always been seen as the main driver. The theory of plant – bee co-evolution though never had any basis – until the discovery of the Burma fossil. Finally, the time of flower origin and diversification and the rise of the bee lined up.

So what made the hunting wasps suddenly turn vegetarian? Most certainly one of them did not suddenly discover empathy and told all its other friends that eating meat was so Jurassic and they should really get into the new, ethical and politically correct pollen diet. More likely, solitary hunting wasps preyed on pollenivorous insects and fed the pollen, which was still attached to the prey, to their larvae. Pollen is rich in proteins, which made the transition for the animals from insects to flower – based food sources easier. The larvae adjusted to this change in diet and steadily, the consumption of insects went down and pollen was first preferred and then essential to survival. The first solitary bee came into be(e)ing.

But how did these solitary insects evolve to be a part of the most intricate and sophisticated social structure today? The origin of the superorganism will be discussed here again next week!

The First Hipster (Hunting Wasp)

I hope you enjoyed the start of this little trilogy and I am looking forward to writing for you again this week. Don´t forget to check in on Wednesday for the Willy-Nilly Wednesday Comic! Till then, I wish you all the best and a great start into the week. Keep your minds buzzing – it´s what they like to do.

References:

A Fossil Bee from Early Cretaceous Burmese Amber

  1. O. Poinar Jr., B. N. Danforth

Science 27 October 2006: 314 (5799), 614. [DOI:10.1126/science.1134103]

The Impact of Molecular Data on Our Understanding of Bee Phylogeny and Evolution

Bryan N. Danforth, Sophie Cardinal, Christophe Praz, Eduardo A.B. Almeida, Denis Michez

Annual Review of Entomology, Vol. 58: 57 -78 (Volume publication date January 2013)

Advertisements

2 thoughts on “(Be)evolution – Where social insects come from

  1. This is fascinating. Is it a meaninful question to ask, if this ecological niche – being pollenivory – was first served be hipster-wasps, or have there been other species co-evoluting at the same time? Keep it going, it is splendid.

    Liked by 1 person

  2. Good question! Wasps, in fact, were not the only (in)vertrebrates to realize the nutritional value of pollen. Evidence shows that thrips, ants, stoneflies, and other creepy crawlies had already been munching on this plant-based food in Permian times (See: “Krassilov, V.A. &
    Rasnitsyn, A.P. 997 03 03: Pollen in the guts of Permian insects: first evidence of pollinivory and its evolutionary significance. Lethaia, Vol. 29, pp. 369-372. Oslo” for more information). Seeing as the Permian period was 298-252 MYA (million years ago) and the Cretaceous Period 145 – 66 MYA, the wasps were actually stragglers in respects to picking up the pollenivory habit. Sort of like the Australian hipsters – the trend is starting to slowly die out in Europe, but down under, it´s just catching on. 😉

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s