The beetle that joined the stones

When it comes to clothes, I am a man of simple means. I don’t much like buying them. I tend to hang onto clothes and wear them for years, until entropy does it thing or washing powder stops doing its thing. New clothes generally come via my wife or as hand-me-downs from a brother-in-law, who does not share my reluctance at getting new items, or, increasingly, from my sons. I sometimes might buy myself a teeshirt that appeals or underpants and socks when the present ones are beyond saving. I think that my eldest son has a similar perspective.

John Marris: not the most obvious place to look for beetles that live under bark. Image from the always well-dressed John Marris.

My other two sons are different. Youngest is a thrifter. He loves combing through thrift shops and second-hand stores to find quality vintage clothing (hey he could do that simply by opening my drawers!). I am not entirely clear on what makes one teeshirt a real find and another not worth a look. He has gotten good at it and now has set up a side business to being a uni student by selling his clothes that he finds online.

Middle son is also interested in clothes. However, he really can’t understand his younger brother’s fascination with the old. Middle likes new clothes. He does like finding a bargain though, and does spend a lot of time searching online for them. This skill has led into his current marketing job. Not to be outdone, middle has set up a side business in selling clothes under his own label (The Loop).

Both sons have a lot of clothes. This is all very alien to me. I guess I can see the appeal of finding a gem on an old clothes rack. That’s is similar to me prowling a second hand book store and finding a classic Tanith Lee or Patrick O’Brian that I don’t already have. I guess I can see the thrill of the new as well. That’s similar to me writing a blog article and putting it onto the net. But clothes?

Practically new! Image from Adrian Paterson

With my parent hat on, though, I am impressed by the fact that the boys have found a passion, and found an opportunity resulting from that passion, and implemented it.

As an evolutionary biologist I am always impressed by examples of organisms that have taken advantage of an opportunity and adapted into a new role. Some of my research has been on these types of organisms. For example, penguins and seals are descendants of land-living ancestors who made the most of an opportunity to become marine again and have prospered by this change.

A neat example has been found by John Marris (Lincoln University), David Hawke (Are Institute) and David Glenny (Manaaki Whenua Landcare Research). Beetles of the Brontini tribe are found all around the world and are almost always are found living under the bark of forest trees. There are abundant resources and safety to be found in this habitat and these beetles specialise in consuming fungi found there. As a consequence of living under bark, the beetles have a very flattened shape.

In an Ecology paper, a new species of this tribe is introduced, Protoden- drophagus antipodes Thomas 2003. A new species of beetle is hardly an earth-shattering event. However, in this case it is definitely not a run of mill species. Protodendrophagus antipodes is the only species of this global tribe to be found in the alpine zone. Specimens have been collected from along the New Zealand Southern Alps from above 1500m in altitude.

At this altitude there are very few food sources. There are certainly no trees and generally no plants either. So where do these beetles live? P. dendrophagus has made the most of its thin shape to find homes in narrow cracks in the rocks found in the alpine zone. The only viable food source that seems to be in these areas are lichens.

Protodendrophagus antipodes – a beetle that left the forest to live among the stones at high altitude. Image from John Marris.

Lichens are composite organisms made from algae or cyanobacteria living among filaments of fungi. In the alpine zone, and in the stony crevices where you find the beetle, there are multiple species and growth types of lichens. But how can you show that the beetles are actually eating the lichens?

A method called isotope analysis can identify the trophic level at which organisms live. Beetles that eat plants and lichens will have different isotope levels to those that eat other insects, for example.

A rocky outcrop with lots of crevices for P. dendrophagus to live in at Mt Hutt. Note that ski fields make sampling at altitude a lot easier to access! Image from John Marris.

P. dendrophagus has made the most of an opportunity. Given it’s adaptations to living under bark, the beetle has taken it’s slimness and invaded the alpine environments where small crevices form a somewhat similar habitat. The body shape for colonising small rock cracks is a pre-adaptation for this habitat. The beetle has taken it fungus eating diet and extended this to the rather more indigestible lichens (that are part-fungi). This has allowed this beetle species to extend its range in the stony zone above the vegetation zone for over 700 km along the Southern Alps.

The team gathered samples from beetles found at altitude at the Mt Hutt ski field. Likely food sources, including several different types of lichen, were also collected. The isotope analysis clearly showed that the alpine beetles were indeed eating the lichens. This a very rare food source for any beetle to eat, with just a handful recorded around the world.

One could say that the new habitat fits like a new glove. Or maybe an old vintage teeshirt.

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