Sunday, 11 November 2012

Non-zero exit status

I have been recently attempting to install and update some new R packages on my Ubuntu 12.10 machine, namely "rfishbase" and "phytools" (and their depends).

Unfortunately I got the fairly opaque error message: "installation of package had non-zero exit status".

After a bit of hunting I realised I was missing some development files from the Ubuntu install that are used to compile the package code. After installing these with the following commands, the packages installed in R no problem.

sudo apt-get update
sudo apt-get install libxml2-dev libcurl4-gnutls-dev libglu1-mesa-dev

Friday, 28 September 2012

Self publishing "failed" thesis chapters on Figshare

Sometimes in life, things just don't work out, and this is especially the case when doing scientific research. Experiments fail, you ran out of time/money, you didn't collect as much data as you wanted, you get a boring negative result, the conclusions are littered with caveats, or maybe the idea was just a duff one in the first place? Unfortunately, one of my thesis chapters ended up suffering from pretty much all of these problems, but is that time I spent on it now wasted?

Perhaps not. The Web site Figshare was set up by a "frustrated Imperial College PhD student" and it looks great (not that I'm biased you understand). It's a "community-based, open science project", allowing "researchers to publish all of their research outputs in seconds in an easily citable, shareable and discoverable manner".

Despite the fact that I felt this chapter was not of the expected quality, rigour, and interest required by a peer-reviewed journal, there are still elements I think would perhaps be useful in the public domain (particularly to aquarists). More importantly though, by putting it in the public domain, an editor, a reviewer, or even myself, doesn't have to make that subjective decision. This is a bit like the PLoS ONE model of publishing, expect without the all-important peer review stage to check that the science is sound. Seeing as I don't really have any strong conclusions other than "more work is required", I can't see much of a problem there.

A hybrid Synodontis catfish. Image used with permission (Mike Norén).

The study is on investigating a simple way to find out if an aquarium fish is a hybrid or not. Hybrid fishes are quite commonly sold in the ornamental trade (especially African Synodontis catfishes), and this has implications for biosecurity agencies who have a responsibility to know which exotic organisms are entering their country. There is also the possibility of fraud, with these "fakes" often passed off as high-value species such as Synodontis granulosa. Finding experts experienced enough to know what they are is hard, and often all they are able to do is make an educated guess based on a photo. One solution is using DNA.

Given a good reference library, mitochondrial DNA with tell you who the maternal species is, but will not itself give you an indication that the fish is a hybrid, or what the paternal species is. Enter nuclear DNA. Microsatellites or SNPs are the best options, but these are too expensive and time consuming for a simple at-the-border test.

What I tried to do was see if a single nuclear gene could give me what I wanted. Results were mixed. It worked nicely for the control (hybrid danios bred in the lab), and some purchased hybrids too. However, for various unexplored reasons, it didn't work so well for the Synodontis (which was really the aim here).

Anyway, see for yourself at Comments are welcome; if they are about self publishing, add them to this blog, if they are about the manuscript use the comment feature on Figshare, and if they are on catfish hybrids, then please add them to the PlanetCatfish discussion thread on the subject.

Friday, 6 July 2012

Research round-up

Unfortunately there has been little activity on the blog of late, mainly due to the small matter of getting my PhD thesis handed in, submitting manuscripts to journals, and finding a job etc! Having said that, I have been somewhat busy in other parts of the Web. Boopboops now has a sister Twitter feed for science related things (@boopsboops), and I have now coded up a Website promoting my CV, publications, and research skills etc, etc.

So, in absence of anything better, and as I've been meaning to do for a while, I thought I'd write about my favourite fish papers of 2009, 2010, and 2011.

(1) Larmuseau et al. (2009) To see in different seas: spatial variation in the rhodopsin gene of the sand goby (Pomatoschistus minutus). Molecular Ecology 10.1111/j.1365-294X.2009.04331.x

I like the idea of looking at how organisms adapt to their surroundings. This study compared variation in the rhodopsin visual pigment locus with phylogeographic patterns in "neutral" mitochondrial and microsatellite markers (i.e. likely to detect any population-genetic structure), and found that in the sand goby, the two were discordant. Variation in the rhodopsin gene (RHO/RH1/RHOD) was partitioned differently and corresponded to photic environment (light penetration, water turbidity etc). There were also signs of positive selection at sites coding for amino acid changes relevant to spectral adaptation.

It's also interesting to note that rhodopsin is a commonly used marker for phylogenetic studies, which is probably due to early studies on vertebrate visual systems providing easy to use primer sets. However, I would be cautious about its use now, as these apparent convergences due to environmental conditions may not give a good indication of common ancestry for a species tree!

(2) Lavoué et al. (2011) Remarkable morphological stasis in an extant vertebrate despite tens of millions of years of divergence. Proceedings of the Royal Society B 10.1098/rspb.2010.1639 

If you've ever kept a tropical aquarium, you may have seen the African butterfly fish (Pantodon buchholzi) lurking in the oddball tanks. They're indeed a strange fish and are great fun to keep, clinging to the surface and greedily snapping up any insects that you feed them. Pantodon buchholzi is the species in a monotypic genus and family, known from the Niger and Congo basins.

When their mitochondrial genomes were sequenced, the researchers estimated that the two isolated populations had diverged over 50 million years ago, despite looking almost identical in terms of shape and meristics!

Evolution is taking place on the DNA clearly, but not on the external anatomy it seems. The reasons as to why and how this has happened are fascinating. The authors state "Proposed mechanisms of morphological stasis include stabilizing selection, ecological niche conservatism and genetic and developmental constraints". I look forward to further studies on this.

(3) Mims et al. (2010) Geography disentangles introgression from ancestral polymorphism in Lake Malawi cichlids. Molecular Ecology 10.1111/j.1365-294X.2010.04529.x

The cichlid flocks of the African Rift Lakes are an almost extreme opposite example to the one presented above. There is huge phenotypic diversity, but often very little in the way of molecular differences. The mbuna cichlids Labeotropheus fuelleborni and Metriaclima zebra, are quite different in appearance, but share mitochondrial DNA haplotypes typical of very recently diverged, or hybridising species. The authors also report "greater mtDNA differentiation among localities than between species".

Information from the nuclear genome can help in these situations of understanding levels of gene flow, but can have limited resolving power when not used in sufficient number. Enter NGS. Modern sequencing methods can now provide orders of magnitude more data, and with a large SNP (single nucleotide polymorphism) set, here the authors report that the two species are indeed genetically distinct, and that recent hybridisation among the two species is unlikely. Certainly a useful tool for exploring these questions further.