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

Bohumiljania of New Caledonia

Today in Zootaxa a paper was published describing a number of species in the leaf beetle genus Bohumiljania from New Caledonia. Unfortunately, these species aren't going to win many prizes in the beauty stakes—they're all pretty nondescript, generic looking chrysomelids (See the picture of Bohmiljania aoupinie above). However, it belongs to a group (the Spilopyrinae), that displays a classical Gondwanan distribution pattern so it will be of interest to those people who are interested in the biogeography of New Caledonia. These beetles tend to be found in mountainous areas, and all known hostplants are in the Myrtaceae.

Incidentally, this is Zootaxa's 3000th issue. Pretty good going for a journal that celebrated its 10th birthday on 28 May this year.


Reference:
Reid CAM, Beatson M. 2011. Revision of the New Caledonian endemic genus Bohumiljania Monrós (Coleoptera: Chrysomelidae: Spilopyrinae). Zootaxa 3000: 1-43. The full 6 MB article is here

Houseflies of New Caledonia and Vanuatu

Over the past couple of months, Marcia Couri and colleagues have published two monographs on the Muscidae of New Caledonia and Vanuatu. These two papers describe six new species with nine other species recorded from the region for the first time. The world-wide house fly Musca domestica (pictured here) is newly recorded from a number of islands throughout Vanuatu.

These papers are important additions to our knowledge of Melanesian flies. They give keys and diagnoses for the genera and species found in each archipelago, and give comments on the wider distribution of the flies found. Unfortunately, there are few illustrations, limited to line drawings of taxonomically important structures of the newly described species. While this may limit their utility to users who don't already have some familiarity with the group, these paper effectively summarize the housefly fauna of the region and provide a good basis for the further study of this important group.


References:
Couri MS, Pont AC, Daugeron C. 2010. The Muscidae (Diptera) of Vanuatu. Zootaxa 2556: 1–39
Couri MS, Pont AC, Daugeron C. 2010. The Muscidae (Diptera) of New Caledonia. Zootaxa 2503: 1–61

New hemipteran species from New Caledonia

In the same issue of Zootaxa describing the manuka scale insect, another hemipteran was described. Teabooma secunda is the second species of the genus (which is endemic to New Caledonia) to be described. It is in the family Cydnidae which are common and widespread. They are frequently mistaken for beetles, and it is usually only a careful look with some magnification that will reveal the mistake. It's a poorly known family, but they are thought to feed on roots, seeds and fallen branches. None are known for their economic importance.

References:

Lis JA, Lis B. 2010. Teabooma secunda (Hemiptera: Heteroptera: Cydnidae)---a new species of a New Caledonian endemic genus with a redescription of T. princeps Distant. Zootaxa 2543: 64-68.