Friday, 22 January 2010

Highly diverse weevils in northern New Guinea

New Guinea is an amazing place. It is one of the final frontiers of exploration, particularly in the biological realm with highly diverse rainforest that cover huge areas and a nearly unbelievable range of habitats from hot, humid mangrove swamp forests to 4,000 m high mountains and glaciers. The diversity of the island astounds everyone who works there and the amount remaining to be discovered absolutely boggles the mind.

A case in point was published late last year, when research on Trigonopterus weevils from the Cyclops Mountains was published. This research was headed up by Alexander Riedel and they looked at the congruence between clades revealed by cytochrome c oxidase 1 (COI) DNA sequences and morphological variation. They found 51 morphospecies which were all congruent with COI data. What is incredible though is the genetic distances within this group. Uncorrected distances between species were incredibly high, the lowest being 16.5% and a mean of 20.5%. Within species variation ranged from 0% (not too surprising), to a whopping 8.8%. To put this in context, a 2% genetic distance is usually bandied about as being the point at which you're thinking that you've got two different species.

This diversity is particuarly impressive when one considers that these results are derived from a single transect in a relatively low area in one mountain range. The authors justifiably expect that more extensive sampling will produce many more species.

Not only are they incredibly diverse, these weevils are also tough. Being cryptorhynchine weevils, their rostrum can fold up into a groove in their thorax when they're disturbed. Unlike most other cryptorhynchines though their elytra are fused together and to the thorax, making them able to withstand extremely high pressure and ensuring that they are very difficult to dissect. This is a problem when dissections are necessary to fully characterise and identify these beetles.

It's a very interesting paper on a really cool group of weevils. Check out the supporting information for habitus photos of the morphospecies and get an idea of the morphological variation in the group.


Riedel A, Daawia D, Balke M. 2010. Deep cox1 divergence and hyperdiversity of Trigonopterus weevils in a New Guinea mountain range (Coleoptera, Curculionidae). Zoologica Scripta 39(1): 63--74.

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