Comparative population genomics in animals uncovers the determinants of genetic diversity

Countless research has provided evidence of genetic diversity being a central component to many conservation challenges. Being able to predict species diversity is therefore a very beneficial strategy which is what this paper aims to investigate. So far the main focus of conservation has been directed on large sized vertebrates. However these popular animals have been shown to represent a very small subset. This study aims to investigate nucleotide diversity of a larger representation of all species which includes the invertebrates. From this we can uncover whether we can predict genetic diversity of a species.

The gap for molecular data across invertebrates still needs to be filled and the first distribution of genome wide polymorphism levels across metazoan trees of life have been presented, 31 Families of animals spread across 8 animal phyla. For 10 individuals in each family high coverage transcriptomic data was produced and a very weak relationship between nucleotide diversity and any of the geographic variables studied were found. Conversely the body size of the stage that an offspring leaves its parents is by far the most predictive variables. Overall the analysis of the paper indicates that species diversity can be predicted by the number of offspring and longevity of a species. The paper also shows that long lived species with a high brooding ability were shown to be less genetically diverse than short lived species.

The study acknowledges the central population genetic theory that a higher effective population size gives rise to higher genetic diversity and shows how empirical evidence gathered from RNA seq data does not support this. A weakness of the study is that it does not mention the impact of crowdedness of ecological niche on reproduction strategy.

Often organisms do not fall neatly into the strict categories of either producing few offspring and being short lived or producing more offspring and being shorter lived, we feel that ecological life histories could be viewed more as falling along a spectrum.

Species that produce small numbers of offspring and have high longevity have lower genetic diversity which could put them at risk. However the strategy of having many offspring has more risks associated with it, as their “quality” is not equal to the offspring of the lower fecundity strategists. The low fecundity strategists have the advantage of being well selected for their environment and thought to be more resistant to changes within it.

Presently, species conservation often prioritises the rare species ,whether endangered or endemic, and focuses on areas deemed as having a high level of biodiversity (large numbers of different species per unit area). This study encourages us to look beyond the species that are already defined as being endangered and to ones that could become wiped out very quickly due to lack of genetic diversity within the species population. Genetic diversity provides populations with resistance to changing environments and  diseases. The ecological strategy of a species could now become a factor in prioritising species for conservation, where DNA data is not available.

The study used extensive evidence and used a variety of  non-model organisms. In future studies more organisms could be included. From having a clear pre-understanding of the future diversification of species, extinction can possibly be avoided.

References:

Romiguier, J, Gayral, P, Ballenghein, M, Bernard, A, Cahais, V, Chenuil, A, Chiari, A, Dernat, R, Duret, L, Faivre, N, Loire, E, Lourencho, J.M, Nabholz, B, Roux C, Tsagokogeorga, G, Weber, A.A-T, Weinert, L.A, Belkhir, K, Bierne, N, Gelemin, and Galtier, N 2014 ‘Comparative population genomics in animals uncovers the determinants of genetic diversity’ Nature doi:10.1038/nature13685

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