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Posts Tagged New Zealand

Rare giant gecko turns up (dead) in mainland sanctuary Hilary Miller Apr 22

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Here’s one from the good news but bad news file:  The good news is that a Duvaucel’s gecko (Hoplodactylus duvaucelii) has been found on the New Zealand mainland for the first time in nearly 100 years.  The bad news is that it was found dead in a mouse trap.

Duvaucels geckos are the largest of our native geckos, and one of the biggest geckos in the world, growing to up to 30cm in total length.  They are found on a number of offshore islands off the north-east of the North Island and in Cook Strait, and were thought to be extinct on mainland New Zealand.  The last recorded sighting of this species on the mainland was near Thames in the 1920s, but subfossil remains have been found on both the North and South Islands, suggesting it was once widespread across the country. 

The dead gecko was found at Maungatautari, in the Waikato.  Maungatautari is a 3400 ha nature reserve ringed with a predator-proof fence, making it the largest pest-free area on the mainland.  Many rare species have been released into the sanctuary, including kiwi, kaka, takahe and hihi, and reintroductions of many more species are planned.  The Duvaucel’s gecko find suggests that there is a remnant nautral population of the species in the sanctuary, which somehow survived the years when the area was overrun with introduced predators. The hunt is now underway for more of the geckos (which will hopefully be found alive).

This discovery shows that you never know what you might find when you protect an area instead of mining it.

More on the discovery on Stuff.

New Zealand’s favourite plant Hilary Miller Jan 15

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Hot on the heels of Forest and Bird’s “Bird of the year” competition comes the NZ Plant Conservation Network’s 2009 favourite plant poll.  The winner was announced just before Christmas but I must have missed it in the Christmas rush.  While voters in the bird of the year poll managed to display a stunning lack of originality in picking kiwi as their favourite, plant of the year voters were somewhat more creative, voting Pingao as their favourite native plant for 2009. 

Pingao (Desmoschoenus spiralis, or the golden sand sedge) plays an important role in stabilizing sand dunes so its likely to become increasingly important in the face of climate change.  Who’d have thought it has so many fans? The shadowy and mysterious Pingao Pressure Group was obviously busy lobbying for votes while Pohutukawa advocates were looking the other way.   

Here’s a picture:

(Photo by John Sawyer, NZ Plant Conservation Network)

Others in the top ten include the tree nettle (Ongaonga) at number 2, Chatham Island speargrass, some traditional favourites like Southern rata, Chatham Island forget-me-not and Kakabeak, and the plant with the best name of all, the fish-guts plant.

Molecular ecologists meet in the Catlins Hilary Miller Dec 03

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Last weekend I attended the 12th Annual NZ Molecular Ecology meeting, held in the Catlins, in the deep south of New Zealand.  NZ’s molecular ecologists have a traditional of holding their annual meeting in beautiful, out-of-the-way places, and this year was no exception with the Tautuku Outdoor Education Centre in the heart of the Catlins being our base.  This year’s meeting brought together 50 researchers from Crown Research Institutes, DoC, and universities across New Zealand (plus a few from across the ditch).  

Tautuku Bay and the coastal rainforest surrounding it provided a stunning backdrop to the meeting, and provided plenty of opportunity for wildlife spotting – the highlight (for me anyway) being a leopard seal which made itself at home on the beach on Saturday. 

Leopard seal taking a break at Tautuku Bay

But enough about the scenery, what of the science, I hear you ask? 

Molecular ecologists use genetic methods to answer ecological questions.  In keeping with this broad definition, talks at the meeting covered diverse topics ranging from systematics of invertebrates to population genetics of native birds.  Theoretical aspects of the processes that underpin many molecular ecological analyses (such as evolution of microsatellite and mtDNA markers) were also given an airing.  As you might expect, studies aimed at improving conservation management of NZ native species featured highly, but some exotic international flavour was provided by talks on toxicity and phylogenetics of poison dart frogs from South America, population genetics of the black rhino in South Africa, and (from scibling David Winter) speciation of land snails in Rarotonga.  There were also a number of interesting talks on species of economic and agricultural importance to New Zealand.  Elisabeth Heeg from Victoria University talked about the population structure and likely origins of Lake Taupo rainbow trout, Marina Mahood from Lincoln explored the possibility of non-invasive sampling methods for genetic monitoring of possums, and Leah Tooman from Plant and Food talked about the global population structure of an invasive pest moth, the light brown apple moth.  

The New Zealand Molecular Ecology meeting is always heavily student-focussed, and for some this was their first opportunity to present their research ideas to an audience outside their own lab.  Genetics Otago sponsored 3 student prizes for the best talks.  Runners up were Davon Callender from the University of Canterbury for her talk on quantifying environmental stress responses in NZ mussels, and Peggy Macqueen from the University of Queensland for her presentation on the phylogeography of pademelons in New Guinea.  The winner was Benjamin Myles from University of Otago for his talk on using molecular clock methods to date the divergence of Parmeliaceae lichens (these include lichens that grow on beech trees).  

It was clear from the meeting that genomics is playing an increasingly important role in molecular ecology research.  Although the traditional microsatellite/mitochondrial DNA marker combination still featured heavily in most talks, many NZ researchers are beginning to adopt next-generation sequencing to develop more and better genetic markers for population studies.  With the increasing availability of genome-level data for a wide range of species there are exciting times ahead for molecular ecologists.

New family tree for moa Hilary Miller Nov 23

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ResearchBlogging.org

A new take on the evolutionary history of the moa was published in PNAS this week.  Mike Bunce from Murdoch University in Perth and researchers from Alan Cooper’s lab at University of Adelaide have combined genetic data from over 260 moa bones with anatomical, geological and ecological information, to revise species relationships among moa and suggest a timeframe and origin for their evolution. 

Determining how many species of moa there are, and how they are related to each other has been a problem since moa were first described in 1839.  Up to 64 different species and 20 genera have been assigned at various times over the last 160 years.  Moa taxonomy has been complicated by the extreme size sexual dimorphism of some species, where females were much larger than males.   The number of moa species has only been able to be clarified in recent years with the advent of ancient DNA studies, which enable researchers to determine whether subfossil remains of different sizes actually represent different species, or male and female forms of the same species.

The prevailing view of moa taxonomy from the 1980’s through to 2002 had moa divided into 2 families, Emeidae and Dinornithidae, which contain 8 and 3 species respectively.  This new study divides moa into 3 families with the most basal moa lineage Megalapteryx (previously part of Emeidae) elevated to sit in its own family.  The six genera remain the same, but only nine species are recognised in this new arrangement.   

Outline of the new moa taxonomy advocated by Bunce et al. (Reproduced from www.pnas.org/cgi/doi/10.1073/pnas.0906660106)

This study also indicates that these moa species are of more recent origin than previously thought.   They appear to have begun diverging around 5.8 million years ago, from a single ancestral species living in the South Island.  This is about the time the Southern Alps were forming, and Bunce and colleagues suggest that the increase in habitat diversity that followed enabled the evolution of different species of moa.  Some of these species began to disperse to the North Island after the formation of periodic landbridges between the North and South Islands from around 1.5 million years ago.  Moa species diversity appears to have then been further shaped by shifts in climate during the glacial cycles of the Pleistocene.   Bunce and colleagues suggest that this pattern of evolution – recent South Island origin, followed by rapid diversification influenced by tectonic uplift, marine barriers, and glacial cycles – may be common to many of New Zealand’s iconic endemic species. 

Bunce, M., Worthy, T., Phillips, M., Holdaway, R., Willerslev, E., Haile, J., Shapiro, B., Scofield, R., Drummond, A., Kamp, P., & Cooper, A. (2009). The evolutionary history of the extinct ratite moa and New Zealand Neogene paleogeography Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0906660106

Genomes galore on the horizon Hilary Miller Nov 10

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When the first human genome sequenced was published in 2003, it represented the culmination of 13 years of work and cost nearly 3 billion dollars to complete.  In the six years since then an additional 55 vertebrate genome sequences have been produced, and the technology has moved on to the extent that sequencing genomes is bordering on routine.  Now an ambitous proposal to sequence 10,000 vertebrate genomes has been launched with an article in Journal of Heredity:

With the same unity of purpose shown for the Human Genome Project, we can now contemplate reading the genetic heritage of all species, beginning today with the vertebrates. The feasibility of a “Genome 10K” (G10K) project to catalog the genomic diversity of 10 000 vertebrate genomes, approximately one for each vertebrate genus, requires only one more order of magnitude reduction in the cost of DNA sequencing, after the 4 orders of magnitude reduction we have seen in the last 10 years . The approximate number of 10 000 is a compromise between reasonable expectations for the reach of new sequencing technology over the next few years and adequate coverage of vertebrate species diversity. It is time to prepare for this undertaking.

The goal of the genome 10K project is to provide a window into vertebrate evolution, by making large scale comparisons across genomes possible.  Over the last 500-600 million years, vertebrates have evolved into a diversity of forms, occupying a vast range of habitats and exhibiting an huge array of differing lifestyles.  A number of biological innovations are unique to the vertebrate line including the adaptive immune system, the multichambered heart, cartilage, bones, teeth and the internal skeleton.  The project aims to enable researchers to investigate the genomic basis of this diversity and innovation:

DNA sequencing has ushered in a new era of investigation in the biological sciences, allowing us to embark for the first time on a truly comprehensive study of vertebrate evolution, the results of which will touch nearly every aspect of vertebrate biological enquiry.

The proposal is still just that – a proposal, put together by a group of museum curators and genomics experts.  Moving forward on the plan will require a large injection of cash (around US$50 million), and for the cost of sequencing a genome to drop to less than US$5,000 a piece – a price tag which is feasible but still some way off.   However the “Genome 10K Community of Scientists” (G10KCOS) has already begun preparing for the project by cataloguing the DNA and tissue specimens already available in labs and museums around the world. 

A potentially more major problem to overcome will be processing and analysing the huge amounts of data that will be produced.  Much of the increase in sequencing power and drop in cost has come from the advent of new short-read but massively parallel sequencing technologies.  These technologies produce several orders of magnitude more DNA sequence in a single run than the traditional technology used to sequence the human genome, but at the expense of the number of consecutive bases sequenced in each read.  The bioinformatics and computing power required to assemble this data has lagged behind the technology so that today the major bottleneck in genome sequencing comes at the sequence assembly stage, not the sequence generation stage.  In an article about the project published in Science, Webb Miller, a computer scientist at Penn State University points out that assembling 10,000 genomes in 5 years will require processing a genome a day. “There’s a real problem here”, he notes.  Even the imminent arrival of “third-generation” sequencers which promise longer reads and even more sequence output will only go some way to simplifying the huge task of assembling and annotating the sequence. 

So what does this mean for New Zealand?  The Genome 10K project aims to sample as widely as possible across the diversity of vertebrates, meaning that many of our iconic fauna will make it onto the sequencing list.  As the sole representative of an entire order of reptiles, tuatara is likely to be high on the list.  For birds, the project proposes to sequence one species from every genus, meaning kiwi, kakapo, a NZ wren (e.g. rifleman), wattlebird (e.g. tui), kea or kaka, stitchbird (hihi) and others will be in line for sequencing.  Similarly our native frogs, geckos, and the lesser short-tailed bat are sufficiently phylogenetically and biologically distinctive that they may be potential candidates for inclusion.  

The Genome 10k project promises to provide a veritable gold mine of data for evolutionary and conservation studies of our native species and many New Zealand researchers will be closely watching developments.  But it also raises some issues:  Where will the samples from our native species come from?  How will iwi concerns about samples being sent overseas, data being released into the public domain and potential exploitation of their taonga be addressed?  Many NZ species are already in zoos elsewhere in the world (tuatara and kiwi particularly) and samples from these animals could conceivably be used for genome sequencing without any input from NZ researchers at all.  No New Zealand based researchers are included in the G10KCOS, and the list of participating institutions from where specimens will be sourced includes only one New Zealand site – the University of Auckland.  The G10KCOS propose a network of around 20 sequencing sites, coordinated by a large data centre to produce the raw sequence data and draft assemblies.  It seems unlikely that New Zealand will house one of these sites but we should take the lead in assembly and annotation of genomes produced from our native species.

Reference: Genome 10K Community of Scientists (2009) Genome 10K: A Proposal to Obtain Whole-Genome Sequence for 10 000 Vertebrate Species. J Hered,  DOI 10.1093/jhered/esp086.

Origins of NZ skinks revealed Hilary Miller Oct 18

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ResearchBlogging.org Most New Zealanders can name at least a dozen or so species of native bird, but how many can do the same for our native reptiles?  If you starting counting and only got as far as 1. tuatara, you’re probably not alone.  Although we are missing some of the major groups of reptiles (like snakes and alligators), we do have a diverse array of lizards.  In fact New Zealand has around 80 different lizard species in two major groups – geckos and skinks (tuatara are not lizards, they are Sphenodontids). 

Around half of our lizard species are skinks.  These are the most commonly encountered native reptiles, being the species most likely to be spotted disappearing under rocks or into long grass on a hot day, and generally being favoured by the domestic moggy.  Now new research is improving our understanding of the origins and evolution of our skink fauna, with some exciting fossil finds and the publication of a comprehensive genetic study. 

David Chapple (formerly of Victoria University of Wellington, now at Monash University) and colleagues have just published a molecular phylogeny for New Zealand’s skink fauna, which investigates the relationships among 32 of our skink species and their closest relatives from Lord Howe Island, New Caledonia and mainland Australia. 

New Zealand’s skinks were previously grouped into 2 separate genera – Cyclodina and Oligosoma.  Oligosoma species are found throughout New Zealand, are diurnal and have pointed heads and long limbs and toes.   In contrast, Cyclodina species are nocturnal or crepuscular, have squarer heads and bodies, and relatively shorter limbs and toes.  However, Chapple’s genetic work shows that there are in fact 8 different clades of skinks that likely evolved from a single ancestral species after it colonised New Zealand from New Caledonia.  There is no clear division between Cyclodina and Oligosoma, suggesting that the differences in morphology that separate these two genera have evolved on multiple occasions.  Chapple’s paper thus spells the end for Cyclodina as a recognised genus – all New Zealand skinks (plus their closest relative C. lichenigera from Lord Howe Island) are now under the genus name Oligosoma.

Oligosoma alani, one of nine species renamed from the genus Cyclodina

Oligosoma alani, one of nine species renamed from the genus Cyclodina

Genetic studies like this can also give us a better idea of how long ago a species diverged from its common ancestor.  By employing a molecular clock, calibrated against a couple of known timepoints (e.g. known fossil ages or timing of islands emerging), researchers can relate the number of changes in DNA sequence between two species to evolutionary time.  Chapple and colleagues used this method to estimate that skinks first colonised New Zealand 16-22 million years ago.  This date conflicts with previous studies, which suggested a much more recent arrival less than 8 million years ago, but fits with some recent fossil finds from central Otago.  The St Bathans area of central Otago is proving to be a goldmine for early miocene (16-19 million yrs ago) fossils, and a recent paper by Lee and colleagues at the University of Adelaide, Te Papa and Canterbury Museum documents several fossil lizard finds that indicate an Oligosoma-like species was present in New Zealand by 16 million years ago. 

Both the genetic work and the St Bathans fossils point to skinks colonising New Zealand not longer after the “oligocene drowning”, a period 25-35 million years ago when  much of the present-day New Zealand landmass was underwater.  Chapple suggests that after diverging from their New Caledonian cousins, ancestral NZ skink species may have survived on now-submerged volcanic islands along the Lord Howe rise and Norfolk Ridge before reaching New Zealand.  Of course, this scenario requires skinks to have dispersed across large distances of open water, which you may think would be a problem for a non-flying, terrestrial vertebrate.  But this is not as unlikely as is sounds - many of our skink species live in coastal areas, amongst material that is often swept out to sea during storms.  They have also been observed swimming in rock pools, and can stay underwater for up to 20 mins.  So its not unreasonable to think they could survive a trip across the ocean on a raft of kelp or driftwood.

Two of New Zealand's coastal skink species, O. smithii (left), and O. suteri (right)

Two of NZ's coastal skink species, O. smithii (left), and O. suteri (right)

The work of Chapple and colleagues has also resulted in the revision of a number of individual species names for NZ skinks - check out the papers for yourself if you want the details.

Chapple, D., Ritchie, P., & Daugherty, C. (2009). Origin, diversification, and systematics of the New Zealand skink fauna (Reptilia: Scincidae) Molecular Phylogenetics and Evolution, 52 (2), 470-487 DOI: 10.1016/j.ympev.2009.03.021

Lee, M., Hutchinson, M., Worthy, T., Archer, M., Tennyson, A., Worthy, J., & Scofield, R. (2009). Miocene skinks and geckos reveal long-term conservatism of New Zealand’s lizard fauna Biology Letters DOI: 10.1098/rsbl.2009.0440

For more about the aquatic abilities of skinks see also: K Miller (2007) Taking the plunge. Forest and Bird 326: 20-22.

Sirocco gives kakapo a bad name… Hilary Miller Oct 04

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There’s not many people who get to see kakapo these days… and even fewer who can say they’ve been shagged by a kakapo. 

 

This video (which is apparently a hit on Youtube) comes from the new BBC series Last Chance to See , part of which was filmed in New Zealand last summer.  I hope the series will be shown in New Zealand sometime soon!

Hat-tip to Bioephemera

Warrior genes and the disease of being a scientist Hilary Miller Sep 15

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The past few days, headlines like “Maori don’t have warrior gene” and “Maori warrior gene debunked” have been all over the media. This has left me with a sinking feeling in the pit of my stomach, and thinking that this sounds a lot like media hype/oversimplification of what is a very complex area of research.  To recap…

Back in 2006, Rod Lea gave a presentation at the 11th International Congress of Human Genetics showing that Maori have a higher frequency of a particular variant of the Monoamine Oxidase-A (MAO-A) gene.  In some studies, this particular variant has been linked with aggression and antisocial behaviour, and one study back in 2004 dubbed it “the warrior gene”.  The media picked this story up, and bandied around headlines like “Warrior gene blamed for Maori violence”, making statements claiming that “New Zealand Maori carry a “warrior” gene which makes them more prone to violence, criminal acts and risky behaviour”.  This is not what Lea and colleagues claim in their original study at all – I’ll talk more about that below.

Anyway, now according to media reports this claim has been “debunked by science”.  When I read this my initial thought was that someone has done another study of Maori MAO-A allele frequencies, and found conflicting results.  But actually this is not the case at all.  The “scientific study” that debunks this claim is actually just a review by Maori academic Dr Gary Hook, published in Mai Review – a peer-reviewed journal of Maori and Indigenous development, but not a scientific journal.  Hook makes some good points, which I’ll talk more about in a minute, but presents no new data and much of his review of the scientific controversy has already been covered in a previous article.

So what is monoamine oxidase, and what did Lea and colleagues actually find in their study? Monoamine oxidase enzymes break down neurotransmitters like serotonin and dopamine, and are therefore capable of affecting mood.  These proteins and the genes that code for them come in two forms – A and B – it is the A form that is the subject of their study.  This gene contains a number of variants, one of which contains a 30 bp repeat (MAO-A30bp-rpt) in the promoter region of the gene.  The number of times this 30bp sequence is repeated affects how active the gene is and therefore how much MAO-A enzyme is produced.  The 3-repeat form (or allele) in particular results a lower level of MAO-A activity and higher dopamine levels.  Several genetic association studies have linked this low activity variant with antisocial behaviour and increased aggression, but the results are rather complex.  The three largest studies have all found that there is actually no relationship between this variant and antisocial behaviour when this is analysed in isolation, but that this allele is associated with behaviour when environmental factors are taken into account.  For example, a study of Dunedin children found that those who who were abused and neglected in childhood were more likely to show antisocial behaviour later in life if they had the low activity form.  It is important to note that the studies that found this effect were all on caucasian males, and studies of other ethnic groups found no such effect. 

In response to the media storm created by their intial findings, Rod Lea and Geoff Chambers presented a brief outline of their work in the New Zealand Medical Journal in 2007.  I haven’t seen the full study published in a peer reviewed journal, but I suspect it may be in the works.  Anyway, their report from 2007 states that they genotyped 46 Maori males, and found that the low activity allele was present at a frequency of 56% – significantly higher than the frequency found in caucasian males.  They also claim evidence for positive selection on the MAO-A gene, implying that the low activity variant conferred an advantage at some point in Maori evolutionary history.  They suggest that this variant “may have conferred some selective advantage during the canoe voyages and inter-tribal wars that occurred during the Polynesian migrations”.  Their evidence for selection comes from a much smaller sample size of only 17 individuals (as individuals without 8 Maori great-grandparents were excluded to reduce the effect of European genes) and it is hard to evaluate from the information given in the NZMJ article.  It is possible that a larger sample would show different results, or that a genetic bottleneck associated with the colonisation of NZ would result in the same pattern as a result of chance sampling of alleles.

The work on MAO-A by Lea and colleagues was part of a study aimed at analysing the MAO-A gene as a genetic marker for alcohol and tobacco response traits in New Zealanders.  An important part of these types of studies is identifying whether there is any ethnic variation in MAO-A allele frequencies that can confound the results.  Thus their motivation was not to find a “gene” for aggression in Maori, and at no point do they claim that high frequencies of the MAO-A low activity variant cause increased violence and antisocial behaviour in Maori.  This is not what they tested, and in fact no other study has tested this either.  In their NZMJ article, they state:

It is important that the incidental formation of this “warrior gene hypothesis” is interpreted for what it is—a retrospective, yet scientifically plausible explanation of the evolutionary forces that have shaped the unique MAO-A gene patterns that our empirical data are indicating for the Māori population.
As alluded to by Merriman and Cameron, the extrapolation and negative twisting of this notion by journalists or politicians to try and explain non-medical antisocial issues like criminality need to be recognised as having no scientific support whatsoever and should be ignored.

The way Lea and Colleagues framed their study did not help their cause though.  They stated that the MAO-A variant has been strongly associated with aggression and risk taking, without adding the qualifiers that this is only in some ethnic groups, and only when previous environmental factors are taken into account.  This, in addition to referring to the MAO-A variant as the “warrior gene”, was bound to get misinterpreted by the media. 

Gary Hook’s article is largely concerned with the cultural issues around branding Maori with a “warrior gene”.  This is an opinion article, not a scientific study, and much of the scientific “debunking” of the warrior gene hypothesis is simply a review of conclusions already presented by Merriman and Cameron in the NZMJ.  Hook’s main point (which I think is good one) is that labelling maori with a “warrior gene” is akin to labelling them with a disease, and that propagating the idea that maori are intrinsically violent is dangerous and unhelpful.  He rightly states

the implications that follow from the “warrior” gene hypothesis should it become fact in the minds of the general public are horrendous

The media attention given to this article will go a long way towards ensuring that this hypothesis does not become fact in the minds of the general public, so in that sense it has served its purpose.

I think Hook does science a disservice though.  In the introduction he states

 It was proposed that the high criminality of Māori was due to the expression of a “warrior” gene that rendered Māori “more prone to violence, criminal acts, and risky behaviour.”

citing both a news article and Lea and Chambers’ NZMJ article.  The media may have claimed this, but Lea and Chamber’s article certainly didn’t.   He also unfairly states

It is one thing for newspapers to promote their fetishes but it is another for scientists to be the source of speculation and fantasy about the nature of Māori

 when the speculation and fantasy came from the media, not the scientists. 

The associated media coverage of this report does nothing for understanding the science, and contributes to the “scientists always get things wrong” attitude that seems to be prevalent out there.   To present the science in this case as a series of black and white facts – first we think they have a warrior gene, and now we think they don’t – is extremely misleading and only adds to the misunderstandings surrounding the original study.

 References:

 Hook, G.R. (2009). “Warrior genes” and the disease of being Maori. Mai Review, 2, Target article.

 Lea, R., & Chambers, G. (2007). Monoamine oxidase, addiction, and the “warrior” gene hypothesis. Journal of the New Zealand Medical Association 120(1250)

 Merriman, T., & Cameron, V. (2007). Risk-taking: behind the warrior gene story. Journal of the New Zealand Medical Association 120(1250)

New Zealand’s walking bats Hilary Miller Aug 12

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ResearchBlogging.orgNew Zealand’s lesser short-tailed bat Mystacina tuberculata is slightly odd in the bat world due to its propensity for running about on the ground instead of flying.  Unlike most bats, which catch their prey while in flight, the lesser short-tailed bat spends much of its time foraging on the forest floor.  The elbow joints in their wings are specially adapted to function as front limbs enabling them to move with rodent-like agility.

Up until now the prevailing view has been that evolution of terrestrial locomotion in our bats was the result of our long period of isolation and lack of mammalian predators – much the same reasons why flightlessness evolved in many of our native birds. However a new study published in BMC Evolutionary Biology has challenged this hypothesis by comparing the anatomy of the short-tailed bat with the fossil remains of a related extinct species from Australia.  This study suggests that terrestrial locomotion evolved in this family of bats before their arrival in New Zealand, and in the presence of mammalian predators.

The lesser short-tailed bat is the only surviving member of the Mystacinidae family of bats, which diverged from other bats between 41 and 51 million years ago.  It is likely that New Zealand’s Mystacinidae bats (which also include the now extinct greater short-tailed bat Mystacina robusta) arrived from Australia sometime after this.  Fossil remains dating to 26 million years ago of Icarops aenae, a now-extinct species from this family, were recently found at the Riversleigh World Heritage Area in northwestern Queensland.

The lesser short-tailed bat

The lesser short-tailed bat

These fossil remains share several distinctive features of their elbow joint with the lesser short-tailed bat.  These features are functionally correlated with walking on the ground, suggesting that Icarops was also adapted for terrestrial locomotion. The presence of shared derived traits in two closely related species, which are absent from more distantly related species, suggests that those traits were present in the common ancestor of the two species.  This suggests terrestrial locomotion evolved between 51 and 26 million years ago, and that the ancestral Mystacinidae bats in Australia were already adapted to terrestrial locomotion prior to their dispersal to New Zealand.  The New Zealand bats do show a greater development of these specialisations, suggesting that further evolution of terrestrial habits occurred in New Zealand.

These ancestral walking Australian bats would have co-existed with a raft of terrestrial nocturnal predators, putting a dampener on the theory that terrestrial locomotion in bats evolves in response to a lack of predators, much like flightlessness in birds.  The authors propose that instead, terrestrial behaviour evolved because it conferred a selective advantage in these species, enabling them to take an opportunistic approach to feeding and have a more diverse diet.

Suzanne J Hand, Vera Weisbecker, Robin MD Beck, Michael Archer, Henk Godthelp, Alan JD Tennyson, & Trevor H Worthy (2009). Bats that walk: a new evolutionary hypothesis for the terrestrial behaviour of New Zealand’s endemic mystacinids BMC Evolutionary Biology, 9 (169) : 10.1186/1471-2148-9-169