NEW ZEALAND REVISITED

[darren.naish@port.ac.uk]

The biogeography and fauna of NZ has been discussed much on this list 
previously - please look for this stuff in the archives: you will 
find what you're looking for. However... John Jackson (who brings 
free beer round to my house, and is therefore my friend;)) says..

(regarding split of NZ from rest of Gondwana)
> Don't some say late K?

If memory serves, most evidence points to a late Cretaceous 
divergence of NZ from the Australian portion of Gondwana. 

>>Did Moas & Kiwi walk there or fly there?

>They could easily have walked.  There were dinosaurs in New Zealand
>which clearly walked here, why not moas?

(Here I go again). 'Moa' is a plural word (like sheep): one moa, 
three moa, a thousand moa. NZ rifted from the rest of Gondwana late 
in the Cretaceous - if you want moa to reach it on foot, then 
flightless moa ancestors must have been around at that time. I do not 
consider it likely that moa are this ancient, but this is just my 
opinion. However, mtDNA evidence supports my view as moa and other 
ratites appear to have diversified far more recently than this. Plus 
the earliest known fossil birds that might be considered ratite 
ancestors (Houde's _Lithornis_ cohort_) are Palaeocene-Eocene, and 
true ratites do not start appearing until the late Palaeocene.

John also said..

> I am aiming at a theory that everything got wiped out on NZ at some 
> time, and recolonised it later.

No way. NZ is stacked full of endemic relict fauna - you are only 
thinking of the tetrapods, but some of the best evidence is from 
invertebrates including insects (NZ stoneflies are among the most 
primitive living insects known), flatworms (heard of 
_Artioposthia_?) and gastropods, and plants. Sphenodonts are probably 
best interpreted as Mesozoic relicts, as are leopelmatid (=ascaphid) 
frogs. Mesozoic mammals probably _were_ present in NZ (there is 
simply no reason why not), but remain unknown.

>  I can just about believe the 
> tuatara, skinks and geckos could have floated there (despite the 
> dodgy currents),

NZ's hoplodactyline geckos probably have invaded NZ after its 
separation - there is no evidence that hoplodactylines were living in 
the late Cretaceous - and so they probably did raft in (they are an 
endemic Australasian group, known also from New Caledonia and the 
surrounding archipelagos - I assume Australia is their centre of 
distribution). But, again, this is debatable, as mtDNA shows their 
radiation to be an ancient one. Exactly how ancient is problematic 
because of calibration problems. 

> but apparently NZ has loads of frogs too. 

I never said NZ has loads of frogs, John: it has 3 or 4.

> Could they have rafted?  

What - the frogs? Frogs cannot raft because of their intolerance to 
salt water (even the most salt-tolerant frog known, _Bufo marinus_, 
cannot make ocean crossings without the use of a boat), strongly 
suggesting that NZ's leopelmatids are relicts. We know that 
leopelmatids were present in the late Cretaceous, so it is most 
parsimonious to assume that they were in NZ during the Upper 
Cretaceous and survived there to the present.  

How frogs got to the Seychelles I do not know.

> Since moas were found early (I'm 
> not sure how early), and since I can't think of any extermination 
> event except an ice-age, which probably postdates the earliest moas, 
> and possibly doesn't fit in with plant evidence, I'm a bit stuck.

Moa have a pathetic pre-Pleistocene record: it goes back to the end 
of the Pliocene and that's it. There is no evidence that they are an 
ancient group of birds. NZ suffered from a number of climatic 
upheavels in its past - most notably the Miocene Drowning, when 
virtually all of the landmass became innundated by the sea - and this 
>presumably< created genetic bottlenecks, impoverishing faunas and 
causing mass extinction. No evidence for the latter because the 
terrestrial animal fossil record on NZ is so poor. 

Glaciation: NZ did indeed undergo something of a glaciation in the 
Oligocene, at the same time as it underwent a profound orogeny (the 
name of which I have forgotten). Rather than being detrimental to 
moa, it has been suggested that these events were key to moa 
diversification. Part of the evidence for this is the apparent 
primitiveness of the Upland moa (_Megalapteryx didinus_) - at least 
one DNA study concluded that this taxon is the most primitive of all 
moa, and we know that it was a montane-adapted, cold-weather 
specialist. 

"Luckily he landed on his head, so he was OK"

DARREN NAISH
darren.naish@port.ac.uk