Back in the mid-1990s, fluctuating asymmetry (FA) was a very trendy subject area in ecology. For those of you who don’t know, FA is the more or less random variations in morphological characteristics that should be perfectly bilaterally symmetric, and these variations are thought to be influenced by (amongst other things) the environmental stress that an organism experiences as it develops. However, since its peak in popularity, interest in FA has fallen somewhat by the wayside. This happened, in part, because like all trends it has to one day come to an end, but also because it was being heavily over-used and linked to almost everything, sometimes based on rather flimsy evidence.
Regardless of this, I’ve often thought that FA has now become a greatly under-used tool in the ecologists armoury, and it was for this reason that this weeks paper of the week caught my eye. Published recently in PLoS One, Maestri et al. (2015)’s paper is titled ‘Niche Suitability Affects Development: Skull Asymmetry Increases in Less Suitable Areas’. It neatly combines both my interest in FA, and one of my other favourite topics, Species Distribution Modelling, and I couldn’t resist selecting it for that very reason.
They hypothesis behind this paper is that animals which live in less suitable habitat, found at the edges of their niche, will be under greater stress than those which live closer better habitat found at the centre of the niche the species occupies, and so should have higher levels of FA. When they tested this hypothesis on a rodent species endemic to the Brazilian Atlantic forest, then found that, as predicted, the FA in skill morphology was negatively correlated with the habitat suitability, as measured using a species distribution model.
As well as having some interesting results, this paper highlights how GIS is starting to play an important role in areas of ecology which we would not traditionally associate with spatial analysis. After all, those studying morphology rarely think about whether they need to consider spatial elements in their analyses, other than broad location where a specimen was collected. However, it is just these types of areas where GIS can provide interesting, and unexpected, benefits, just as it did for Maestri’s study of fluctuating asymmetry.
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Dr Colin D. MacLeod,
Founder, GIS In Ecology
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GIS In Ecology 