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Postcards from Rangitoto

The views expressed are those of the author and are not necessarily those of Scientific American.


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A week and a half ago I stepped off a plane and into the Southern Hemisphere for the first time in my life. In spite of 12 hours of cramped legs and loud children heedless of fellow travelers’ sleep needs, it was an exhilarating feeling. Location: New Zealand. Though David Attenborough ably prepared me for some of the wonders I could expect to see down here (helloooooo glow worms!), it has still exceeded expectations.

We’ll be taking a bit of a break from the heavy stuff for the next few weeks as I wander New Zealand, Australia, and a couple of obscure Pacific Islands in search of new life and reliable internet connections. As I travel down under, I’ll be posting photo dispatches of the biological highlights of my travels with (hopefully) amusing commentary. So sit back, relax, and enjoy the pretty pictures of Stuff I Found Biologically Entertaining Down Under.

This is Rangitoto Island. It’s a dormant volcano in the vicinity of Auckland, NZ, that probably formed about 600 years ago, in the memory of Maori — the first inhabitants of New Zealand — in the area, but before Europeans arrived. As a result, it’s still in the process of being transformed from a raw lava field into a fully forested island. This is very important process biologists call primary succession, which is to say a lot of ink has been spilled over it. It may even mimic in a very general way the dynamics of the way life evolved on Earth. On Rangitoto, a lot of the lower slopes still look like this:

Here’s what the trail to the summit through the lava fields looks like, with a view of the summit in the distance:

Unfortunately, lots of non-native mammals were introduced by Europeans in a repeat of the story of many islands across the world (see Hawaii and the Galapagos for other notable examples). When the Maori first arrived in about 1000 A.D., settling the last of the major land masses on Earth to be inhabited (remember that the Roman Empire had already risen and fallen for 600 years, and Oxford and Cambridge were just being built! New Zealand is in an odd and perhaps unexpected spot), New Zealand’s only land mammals were seals and bats. Now there are rats, mice, stoats, and lots of other stowaways that have messed with the ecosystem of flightless birds and unusual plants and trees. On Rangitoto they are trying to eliminate these pests to return the island to a more natural state. Hence, there are rodent traps all over the island. Here is one, complete with tasty-looking egg:

This one is apparently for trolls. I can understand how they would also be a nuisance:

Lichens are among the first species to tackle new naked rock, and biologists have long speculated the lichen association — fungus + alga — may be one of the first forms of life to have evolved. This was the first one I encountered on the island, and I thought it might be some strange new orange species.

But after encountering this shortly thereafter, I concluded it was a recently expired version.

Here’s a lichen that in the northern hemisphere I’d call a reindeer lichen, or a Cladonia sp. Down here, not so sure. It was spongy and soft.

Here’s another little gorgeous lichen. No idea what it might be. It looks as beautiful and delicate as some cave crystals I have seen.

And another, which looks like another Cladonia (they get around!). The brown structures resemble the British soldiers lichen we have in North America.

One of the unofficial symbols of New Zealand is the fern. In my week in the country, I discovered why. DAMN, New Zealand. You got FERN. Big ferns, small ferns, weird ferns, thermal ferns. I now understand why the pride of New Zealand, the rugby team called the All Blacks, displays a silver fern on their flag.

One of my favorite things about ferns (other than the fact they have secret little sexual forms that live hidden in the soil) is that they make their asexual spores in special structures usually found on the underside of leaves. It’s a very complicated production that I’ll describe in a separate post, but the whole thing is referred to as a sorus (pl. sori). I have endless fun doing what I call “looking under the fern’s skirt”, i.e., lifting up the leaf to see what those structures look like. And in New Zealand, they look like a fabulous array of things. For example . . .

Here’s one fern that looks like someone either embossed it or hybridized it with bubble wrap.

But turn it over and you find the sori.

Here’s one that isn’t quite ripe yet.

I discovered little forests of these gelatinous looking little ferns covering the ground as well. Note dead leaf for scale:

Here’s a closeup:

According to a sign on the island, the species is Hymenophyllum sanguinolentum, or the filmy fern. Perfectly named! The leaves are probably only a few cells thick, as you can readily see your fingers from the other side. I couldn’t find any sori.

At this point, it’s probably worth saying a little bit about ferns and fern biology so you can understand better why I’m so excited by these things. And so before I proceed with my most spectacular fern findings from Rangitoto (and a few other fun sights), we’ll take a sub-, sub-break to talk a little bit about the basic biology and very confusing sexuality of ferns. Next time.

Jennifer Frazer About the Author: Jennifer Frazer is a AAAS Science Journalism Award-winning science writer. She has degrees in biology, plant pathology/mycology, and science writing, and has spent many happy hours studying life in situ. Follow on Twitter @JenniferFrazer.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Christopher Taylor 5:22 am 04/29/2012

    Here’s one fern that looks like someone either embossed it or hybridized it with bubble wrap.

    Phymatosorus, if I remember my undergrad botany correctly. Not sure of the species: may be P. diversifolius.

    The leaves are probably only a few cells thick

    One cell thick. Honestly.

    One really cool thing about Rangitoto: When you walked to the summit, do you recall crossing a ditch about two-thirds of the way up? You can see the ditch in question on the photo of the island, as it rings around the cone. The steep cone inside the ditch is formed of the ash that came up in the first explosive part of the eruption; the gentler slopes outside the ditch are from the lava flows once the eruption had settled down a bit. Because of the difference in the rock types, the ground on the cone is considerably drier than on the slopes. When you cross the boundary between the two, you can almost see a line as the filmy ferns and kiekie growing on the damper slopes stop short, and are replaced by the bracken and tea-tree on the drier cone.

    Link to this
  2. 2. kdimoff 2:16 pm 04/30/2012

    beautiful ferns and lichen! fern sori fascinated me as a kid growing up in the oregon coastal range. i was reading this wishing you were on instagram, sharing your finds :)

    is there any way a lichen ever gets a rust?

    Link to this
  3. 3. Jennifer Frazer in reply to Jennifer Frazer 10:44 pm 05/1/2012

    Christopher — Yes! I absolutely subconsciously noticed that, though I hadn’t thought about it per se. I also thought of mentioning how that ditch around the cone was formed as the central cone slumped as it cooled. I think that’s right, anyway; the signs on the island said something to that effect. Thanks for the extra info — very cool!

    Kati — I have never seen a lichen get rust but that doesn’t mean it isn’t possible. In my experience, rusts are obligate parasites of plants. Since plants are so distantly related to lichens, it would seem unlikely that rusts could make that jump. But not impossible! I’m continually amazed by the evolutionary distance that a single rust species can span in its hosts. There are, I believe, rusts that parasitize ferns, but flowering plants are their alternate hosts. That’s several hundred million years of evolutionary distance between the hosts!

    Link to this

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