An R function for finding coordinates of NZ localities

Over the course of my PhD, I will be doing a fair amount of georeferencing. This involves obtaining geographic coordinates for localities where weevil specimens have been collected. When I'm the one who has collected them, this is fairly straightforward—Google Maps has made obtaining coordinates a breeze. When it's a museum specimen, however, things get a little tricky. Maps and atlases are extremely useful, but hard to search through. The university has access to MapToaster which contains the topographic maps of New Zealand, and which allows one to search for place names. However, it's only available from university computers, and the search feature requires a degree of mouse work to drive it. LINZ has made the New Zealand Geographic Place Names Database freely available online, which is also fairly fiddly to use in a high throughput situation. However, it is based on a fairly well-structured database, which allowed me to write an R function to search and retrieve information (including coordinates) for place names of interest.

The result is gazNZ(). This function allows a name to be searched for from the R console, making the process of finding coordinates a lot quicker, and means that I only need to use my keyboard when searching for things—a much more satisfying state of affairs.

> gazNZ("Cook Strait")
Read 201 items
Read 211 items
$`Cook Strait`
[1] -41.2493 174.4736

Panbiogeography of New Caledonia

Two weeks ago, I reviewed Nattier et al's paper concerning the dispersal of the eneopterine crickets to New Caledonia. This week I discuss the opposing view of Michael Heads, who vociferously promotes the idea that the biota of New Caledonia has its origins in a vicariance framework; i.e. plate tectonic processes have had more of an influence on organism distribution than chance dispersal processes. In particular, Heads is a practicioner of the method known as panbiogeography—a method that emphasises the importance of recurring patterns in the distribution of organisms.

After giving an overview of New Caledonian geology, Heads discusses the various distributional patterns displayed by a variety of taxa in New Caledonian mainland, including the Loyalty Islands. He identifies 10 primary patterns, which can be broadly summarised as restricted to the Loyalty Islands; shared between the Loyalty Islands and Grande Terre; and distributions corresponding to the geology of Grande Terre. Of particular note is his observation that the strange shrub Amborella is restricted to central Grande Terre, on what Heads calls the basement terranes.

I enjoy reading Head's papers. His perspective is an interesting one, his promotion of mapping distributions and having an understanding of geological processes is important and his papers are full of fascinating examples. However, I do see a something of a contradiction in some of his views. He's a proponent of the metapopulation theory, whereby organisms jump between islands that are emerging and disappearing as part of island building processes, resulting in organisms having a longer evolutionary history than the islands that they currently inhabit. I don't have problems with that. However, once land gets accreted, his explanations rely on organisms remaining on those terranes, and not moving far from them at all. The combination of these two views sits somewhat uneasily with me.

Biogeography is a fascinating subject. What I also find amazing is that debates regarding biogeographic processes and methods become incredibly passionate. Panbiogeography is one of those sub-disciplines that is fiercely defended by its proponents and viciously denigrated by its critics. I don't count myself in either camp, preferring to take the useful bits out of any research and always bearing in mind that our perception of the past will always be incomplete, and that discussions regarding the past should be conducting in the light of that fact.

References:
Heads M. 2008. Panbiogeography of New Caledonia, south-west Pacific: basal angiosperms on basement terranes, ultramafic endemics inherited from volcanic island arcs and old taxa endemic to young islands. Journal of Biogeography 35: 2153–2175

Dispersal of crickets to New Caledonia

An eneopterine cricket in the genus Cardiodactylus. Photo courtesy of Guido Bohne

New Caledonia is one of the largest islands in the Pacific, being exceeded only by New Guinea, New Britain, and the main islands of New Zealand. Like New Zealand, the composition of the biota, which includes several relict groups such as the Amborella shrub and the Kagu (Rhynochetus jubatus), has lead many to believe that the island is a fragment of Gondwana, with a long biological history. Also like New Zealand, this story has been questioned in recent years by geological evidence that the island underwent submergence at various points in its history, and that the biota is a result of long-distance dispersal. Cue a classic dispersal-vicariance stoush that is a trademark of biogeographic discussion.

In the dispersal corner is Romain Nattier and coauthors, who present evidence of a "recent" arrival in New Caledonia of the eneopterine crickets. This subfamily of crickets have a wide range throughout several islands of the Pacific, South-East Asia and South America. Their analysis of four genes show that the New Caledonian eneopterine crickets are most closely related to species on other Melanesian islands, and that they've likely been in New Caledonia for "only" 5–16 million years. They then use this evidence to indicate argue against an ancient presence of New Caledonia.

I've got no quarrel with their conclusions regarding this group of crickets. The evidence for a recent arrival of these guys seems pretty clear. However, I do wonder why the authors chose this group of insects to test their hypothesis. The distribution of the non-New Caledonian species suggests that this group is fairly vagile. Their presence in archipelagoes such as Vanuatu, a young island group by most people's standards, hints at their dispersal ability. Much more convincing with regard to their New Caledonia drowning hypothesis would be one of the groups that is less likely to move around as much. Of course, with this criteria, the taxon of choice would be likely to be one of the relict species—which by definition are species poor and with few close relatives—leading to a biased outcome.

I was surprised that none of the Australian representatives were closely related to the New Caledonian crickets. An Australia–New Caledonia link is a fairly common pattern in New Caledonian biogeography, but it hasn't held up in this instance. I was also surprised by the sister-taxon relationship between a genus in Fiji and Samoa, and a couple of genera in Central and South America. Those sorts of relationships seem fairly strange, but not too much stock can be placed on it without knowing more details about the group, and the sampling regime used in the study.

As always, this is not the last word on the subject of the origin of New Caledonia and its biota. It isn't even the definitive on the evolution of this group of crickets. This is one piece of the puzzle that is New Caledonia's biota, and one that will illuminate further research on the natural history of the island, as well as being a valuable addition to the literature of eneopterine crickets.


References:
Nattier R, Robillard T, Desutter-Grandcolas L, Couloux A, Grandcolas P. 2011. Older than New Caledonia emergence? A molecular phylogenetic study of the eneopterine crickets (Orthoptera: Grylloidea). Journal of Biogeography 38: 2195–2209

Crosby Codes

Entomologists with any interest in the New Zealand fauna will no doubt have come across the two-letter codes affectionately known as "Crosby codes". These codes denote geographical regions in New Zealand and are used for the purposes of grouping and retrieving specimens. They are named after Trevor Crosby, the lead author of two papers in 1976 and 1998 where these codes were defined. The 1998 paper expanded the codes to include New Zealand's offshore islands, and includes written descriptions of the boundaries between each region.

The codes have proved to be very useful in the entomological context, and have also been used in many other fields where the distribution within New Zealand is important.

Reference:

Crosby TK, Dugdale JS, Watt JC. 1976. Recording specimen localities in New Zeland: an arbitrary system of areas and codes defined. New Zealand Journal of Zoology 3:69 + map.

Crosby TK, Dugdale JS, Watt JC. 1998. Area codes for recording specimen localities in the New Zealand subregion. New Zealand Journal of Zoology.25:175-183

Blood parasites in Melanesian White-eyes

The white-eyes are a group of small birds in the genus Zosterops with an interest out of all proportion to their size. As a genus, they range from Africa, through Asia and Australia to many islands in the Pacific where they are fairly common. In the islands they have diversified to the extent that most archipelagos have at least one endemic species present. This is most impressive in the New Georgia group of the Solomon Islands, where six species are present over six different islands---many of which are separated only by a few kilometres of ocean. Additionally, one particular species, the silver-eye (Zosterops lateralis) has a wide range across Australia and into the central Pacific As such, there are many different questions regarding their dispersal, rate of speciation and the relationships between the different species.

In a paper by Farah Ishtiaq and coauthors, the birds themselves are not so much of interest. Rather, it's the prevalence of parasites in the blood of the birds found in Vanuatu and New Caledonia. More specifically, they look at the protozoans Plasmodium (more commonly known as avian malaria) and Haemoproteus that are spread from bird to bird by blood-sucking flies and mosquitoes. They took blood samples from a number of specimens, comprehensively sampling five different species of white-eye from Vanuatu (13 islands represented), mainland New Caledonia and the Loyalty Islands. Within these, they found seven different lineages of Haemoproteus and 14 lineages of Plasmodium. Most lineages were fairly scarce, with one lineage of each parasite genus being the most common and widespread.

When they looked at the number of parasite lineages on each island, they found that the larger islands had more lineages of Plasmodium than smaller islands. This trend was much less evident in Haemoproteus, being not statistically significant. The pattern of increasing numbers of lineages or species with increasing island area is a very well-known relationship that forms the basis of the Theory of Island Biogeography, first postulated by Robert MacArthur and EO Wilson in the 1960s. It is interesting that these parasites show the pattern also, despite the additional variables of requiring a host and a vector insect to be present.

Why is this of interest? Parasites have a huge effect on their hosts which is often invisible. They are also a part of the natural heritage of this world and so are worthy of study in their own right. These findings share a small glimpse into a world that is usually hidden, and increases our awareness of the biota of the Melanesian region. As with a lot of scientific research, progress is incremental with many small, initially insignificant findings building into a body of knowledge that can be extremely important for health, conservation, or technological impact.

References:
Ishtiaq F, Clegg SM, Phillimore AB, Black RA, Owens PF, Sheldon BC. 2010. Biogeographical patterns of blood parasite lineage diversity in avian hosts from southern Melanesian islands. Journal of Biogeography 37: 120-132.

Featured insect: Aureopterix micans (Lepidoptera: Micropterigidae)

The moth fauna of the Pacific is still fairly unknown, with most of the work that's been done on the region's being rather old and with few recent revisions. An addition to the literature was recently published by George Gibbs in Zootaxa today on the Micropterigidae of Australia, New Zealand and New Caledonia. In it, he describes the species pictured:

Aureopterix micans from New Caledonia. This beautiful species is fairly widespread and common throughout New Caledonia at moderate altitudes.

As suggested by the name of the family, the Micropterigidae are part of the microlepidoptera---an informal name for a bunch of families that are small and tend to escape the notice of the public. They also tend to escape the notice of most specialists, and so their biology is not particularly well known. This is true for Aureopterix micans, however, the larvae for some of the other species described in the paper are known to feed on foliose liverworts. This is likely to be true of A. micans also.

It is believed that the distribution of the Micropterigidae may offer insights into the biogeography of the South Pacific region. The distribution of Auropterix offers a fairly standard interpretation of New Caledonian biogeography. While A. micans is restricted to New Caledonia; the only other species currently known in the genus, A. sterops, is found in northern Queensland, Australia. This East Coast Australia---New Caledonia connection is fairly typical of a lot of the fauna of the island. Other species of Micropterigidae however do not show this pattern, being closer to species in New Zealand than Australia. While Biogeography is full of interesting details such as these, going from hypotheses of pattern to process can be difficult to test, and will require greater research into the fauna of each area and underlying geology and ecology of the species involved.

References:

Gibbs GW. 2010. Micropterigidae (Lepidoptera) of the Southwestern Pacific: a revision with the establishment of five new genera from Australia, New Caledonia and New Zealand. Zootaxa 2520: 1-48.