Zombies of Zealandia? A Halloween review of the Ghosts of Gondwana

(This review was published in the New Zealand Ecological Society newsletter no. 160, July 2017, pp 22-24)

 

Just not cricket? Image from Adrian Paterson.

Earlier this year I was in the Southern Alps with a first year field trip where we look at the geology of the region and what it tells us about the biological history and current ecological processes of the area. Many students are energised by this look at the past and present and wanted to know where they can read more about New Zealand biogeography. It’s an easy answer. Get hold of George Gibb’s Ghosts of Gondwana. It’s been something I’ve been saying for a decade.

Gibbs has now fully revised his 2006 book Ghosts of Gondwana: the history of life in New Zealand. The first edition was an excellent introduction to the biological and geological history of New Zealand. So much information was packed into that book, and it was so elegantly packaged with great diagrams and frequently stunning photographs. Even the paper it was printed on was first rate! Perhaps the best judge of the worth of a book like this is by how much it is read. My copy was constantly borrowed over the last decade (in fact whoever borrowed it last has neglected to give it back!).

With the revised edition we get what feels like the Director’s cut. The book is 50% longer. The dimensions are larger, the paper quality is sumptuous. There are more photos and diagrams and more examples. Research over the last decade has been added. This will be one of the nicest looking books that you put on your shelf.

The book is divided into four sections. The first section is a short introduction to what makes New Zealand unique. The second section primarily looks at the tools by which we examine and reconstruct the past (fossils, phylogenetic trees, biogeography and so on). This section is quite technical but well explained and welcomed because of it. The third section is an overview of the geological changes over the past and the impact on the NZ biota. The final section looks at how evolution has been at work in our shaky isles. This is my favourite part of the book. There are lots of clear, well described examples of evolution shaping taxa from singing in cicadas to moa browse and plant traits. I can see much of this going into future lectures.

Hosts of Gondwana would be an interesting but different story. Image from Adrian Paterson.

The main change since the first edition is to remove some of the focus on the recent past, particularly on phylogeography. This is a good move that allows the focus to be on the distant past that shaped our biota. One good consequence is that this has emphasised the concept of Australis (basically east Gondwana) that seems like it should have had more visibility since the first edition (in a similar way that Zealandia has become a major part of our lexicon over the last decade).

Despite all of the good content in this book there were a couple of main areas of frustration. The first was the prominent and consistent mention of panbiogeography and the work of its practitioners. I won’t go into the specific arguments against this approach to understanding species distributions as George makes the main point himself when he says that as panbiogeographers’ “arguments are based on a different kind of logic that is not amenable to scientific testing, they are disregarded by many, especially the molecular proponents, as being non-scientific” (p. 170). Exactly. Hence, it is frustrating to see that this approach is then scattered throughout a book that is focused so heavily on scientific thinking.

The second area of frustration was with the attitude towards molecular data and the molecular clock in particular. Molecular data is now a common tool in ecology and evolution studies. In biogeography it is the main tool. It is disconcerting to be told that there are scientists working with molecules “that would scarcely be able to recognise a living example if they met one in the field” (p. 48). I can’t say that I have ever come across anyone like this and it feels fairly disrespectful to those that make use of molecular tools in their work (which is most people in this area these days).

‘Weta’ good book! Image from Adrian Paterson.

The view on molecular clocks generates even more frustration. Being able to (roughly) estimate timing of last common ancestors has revolutionised biogeography. For example, the term ‘Gondwanan’ can be used in at least three different ways. First, a taxon is Gondwanan if species are currently found in former Gondwana landmasses (pattern). Second, a taxon is Gondwanan if the lineage has been continuously present in New Zealand since Zealandia broke away from Gondwana (or Australis), say 55-80 million years ago (pattern and process). Third, a taxon is Gondwanan if it is descended from a lineage that was present in Gondwana (Australis) prior to the break-up but successfully dispersed to New Zealand after Zealandia broke away from Gondwana and sank, i.e. in the last 20 million years (pattern and process). The only way to test between the second and third explanations is through estimating time of divergence. If a New Zealand lineage has a common ancestor with an Ausz  tralian lineage dated at around 5 million years ago then the lineage had to have dispersed. If a New Zealand lineage has a common ancestor with an Australian lineage dated at around 75 million years ago then the lineage is likely to have been present in Zealandia/New Zealand for this time. Timing is everything in answering which meaning is accurate.

Molecular clocks, even when relaxed, have error. But the error is not such that you cannot tell the difference between 50 and 10 million years ago. Throughout the book we see a lot of distrust with regards to the molecular clock with comments like ‘whether it can be trusted or not’ (p. 98), ‘its flaws are seldom debated’ (p 151), ‘a questionable calibration process’ (p. 180) and so on. As Gibbs sums up the book he says ‘I have used maps of the past, patterns of world distributions on those maps, systematics and phylogenetics, tectonic geology, the fossil record, molecular data, even the clock hypothesis with all its faults’ (p. 315). It is worth noting that ALL of the things mentioned here have error associated with them, most with errors at least as broad as the molecular clock!

In discussing the above concerns I feel like I am coming across as overly negative. Overall, this is a good and useful book. I am considering whether to make it a text for my first year course. The book is definitely pitched at a suitable level for undergraduates, those who want to learn more about New Zealand, and offers much to ecologists who want an evolutionary and geological background to their focus ecosystems. My workplace will soon be moving to an open office environment and we academics will only have space for about 10 books at our desks. Will Ghosts make the cut? Absolutely (probably so that it can be lent out to others!). If you have any interest in the history of New Zealand from a biology or geology perspective you should get this book. In fact, buy two copies and give one away. The recipient will thank you. If you have a copy of the first edition, do you need to get this one? Absolutely. The last decade has been one with a lot of work in this area (Oligocene Drowning, Miocene mammal fossils, relaxed clocks) and for the update alone it is worthwhile. Where to next for George? Ghosts of Gondwana is definitely not the last word on evolution in New Zealand. Perhaps there is scope for a sequel: the Apparitions of Australis or the Zombies of Zealandia?

GHOSTS OF GONDWANA: THE HISTORY OF LIFE IN NEW ZEALAND

(FULLY REVISED EDITION)

George Gibbs. 367pp.

Potton and Burton, ISBN 978-0-947503-08-6, 2016

Reviewed by Adrian Paterson

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