Archive January 2010

saying a lot about little – another example of how not to use statistics Alison Campbell Jan 11

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Ben Goldacre has written an interesting post on a ‘news’ item comparing pay scales for UK workers in the public & private sectors. The original story drew a number of comparisons between the two, several of which turn out, on closer examination, to be spurious. For example, the item comments that public servants work fewer hours than those in the private sector – but as Ben points out, in the UK there is a higher proportion of part-time workers in the public sector, & those doing the analysis hadn’t bothered to distinguish between the two but lumped them all in together. The story also suggests that public sector employees in the UK are paid more than their peers in the private arena. But this comparison is also a tricky one, because many state-employee roles don’t have an exact match with private sector positions (policemen & firemen, for example). And this works both ways: some of the lowest-paid UK private sector employees work in retail – not something the state sector is involved in.

So, another example of the need for caution when interpreting statistical data. (And worth remembering next time private:public comparisons are made here in NZ…)

cauliflory (but not with cheese) Alison Campbell Jan 10

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Plants have a fascinating array of adaptations that function to maximise the odds of successful reproduction. Flamboyantly shaped & coloured flowers spring to mind, not to mention nectar rewards & attractive scents (which are not necessarily pleasant to the human nose, but then, Rafflesia isn’t out to attract us!). One of the more unusual adaptations is cauliflory – the flowers are produced on the main trunk or branches of the plant, rather than on a separate flower stem. (Ironically, cauliflower is not an example of a cauliflorous plant. That tightly bunched white head – so yummy with a nice tasty cheese sauce - is derived from a ‘normal’ flower, borne like a lily, orchid or rose on a young leafy stem that develops from an apical or axillary bud.)

I hadn’t come across cauliflory until our trip to the Daintree while on holiday. (Either I didn’t learn about it way back when, or the information fell out the back of my head once exams were over…) Our guide drew everyone’s attention to this tree, a red mahogany:

cauliflory, full trunk.JPG

Those red-gold balls on the trunk are the fruits of this particular species, produced from fertilised flowers that were held on short stalks just above the bark.

cauliflory close-up.JPG

How would this particular adaptation have evolved? After all, ‘typical’ flowers are held out there where they can be easily found by pollinators (or, if they’re wind-pollinated, their anthers hang out there in the breeze). But this ignores the fact that many animals live on the tree trunks themselves – the Boyd’s forest dragon I wrote about earlier is just one example. The ‘stem flowers’ of cauliflorous plants are easily accessible to any animal moving about on the trunks below the forest canopy, & this type of flower turns out to be relatively common among rainforest trees, where mammals, birds, reptiles & insects all act as their pollinators. Around 100 different species are cauliflorous, something which seems to have evolved on more than one occasion as it’s found in many different plant families in the tropics (caulifory is less common in temperate-zone plants).

So – something else to add to my lectures this year :-) And hopefully my students will absorb the information better than I did!

a wide froggy mouth – but not on a frog Alison Campbell Jan 08

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 When I was an undergraduate a joke about wide-mouthed frogs went the rounds…

Frog mouths are quite interesting, actually. Look into that gape & you’ll see a tongue (which is rooted at the front of the mouth, allowing it a greater forward reach). Back of the tongue is the glottis, opening into the trachea, & behind it the entrance to the oesophagus (showing, yet again, that if life was designed then the designer did a fairly poor job of it – having the airway & food passage cross over in the back of the throat is not really a good thing…). And on either side, in from the jaw joint, are the openings to the eustachian tubes that link the throat & inner ear. Another thing I find fascinating is that if you look at the roof of a frog’s mouth, you’ll see two bulges that mark the underside of the eyeballs. (Once a zoologist, always a zoologist…)

But this post is about another type of frog mouth altogether. Or, to be correct, a frogmouth:

papuan frogmouth.JPG

This is a Papuan frogmouth – we saw a pair of these lovely little birds at the Habitat in Port Douglas. They might look vaguely owl-like, but frogmouths are only distantly related to owls. Their feet are smalled & weaker, and while they’ve got good night vision their eyes aren’t as big as those of an owl. Frogmouths are usually nocturnal, but the two we saw were sitting amiably in a corner of the ‘breakfast with the birds’ area, & in fact we encountered them on our way through to the savannah habitat after a most excellent breakfast (with the birds – if you go there, watch out for the ibis as it’ll pinch unguarded sausages!). They were quite tame & one was happy to hop onto the keeper’s arm – you can see those little toes, quite unlike an owl’s talons.

papuan frogmouth & keeper.JPG

As the name suggests, a frogmouth’s mouth has quite a wide gape, Their main food is insects but apparently they’ll also take rodents & small lizards, swooping down silently to catch their prey. You can see in the photos that a frogmouth’s plumage has a soft, almost indistinct look to it – & it’s not because my photos are blurry! The ‘soft’ structure of owl feathers apparently underlies the typically silent flight of an owl (such as our own morepork), & I wonder if the same principle is operating in the frogmouths. And in the daytime, that fuzzy, indistinct plumage would provide excellent camouflage while frogmouths sleep in their roosts.

We saw a lot of bird species at the Habitati, but I think overall the frogmouths were my favourites – they were such engaging little things :-)

trees on stilts Alison Campbell Jan 04

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And no, I’m not talking about triffids here. More a part of the continuing series on plant root adaptations. I’ve mentioned mangroves in passing before (to do with their pneumatophores), but the thing that stood out for me about the mangroves we saw in Queensland was the fact that they looked like they were on stilts:

mangroves at low tide.JPGThese trees looked quite different from the familiar NZ mangrove. Mangroves here belong to a single species, Avecennia marina, which is found around the coastline of the top third of our North Island (reaching its southern limits – linked to average daily temperatures - in Kawhia & Ohiwa harbours). A.marina is just one of a group of species grouped under the name ‘mangroves’ (around 30 different species in Australia), characterised by their habitat as much as anything: they grow in muddy intertidal zones along coastlines & in estuaries. That is, ‘mangrove’ is an ecological rather than a taxonomic classification. ’Our’ mangrove differs from the ones we saw over the ditch in that ‘theirs’ have those rather wonderful stilt roots.

Well, some of ‘theirs’ do. It seems that mangroves can be put into 3 groups: ‘red’, ‘black’, & ‘white’ mangroves. The ‘red’ mangroves grow closest to the water and put down stilt-like ‘prop’ roots, like the ones shown above. ‘Black’ mangroves – belonging to the genus Avicennia – put up pneumatophores to allow them to obtain oxygen from the atmosphere. They tend to grow inland of the ‘red’ trees. "White’ mangroves grow even further inland & don’t usually have either type of specialised roots.

I learn something new every day :-) 

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