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bioRxiv · 10.1101/2020.11.16.382945

Population genetics of transposable element load: a mechanistic account of observed overdispersion

Smith, R. D.·Puzey, J.·Conradi Smith, G. D.
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Abstract

In an empirical analysis of transposable element (TE) abundance within natural populations of Mimulus guttatus and Drosophila melanogaster, we found a surprisingly high variance of TE count (e.g., variance-to-mean ratio on the order of 10 to 300). To obtain insight regarding those evolutionary genetic mechanisms that are may underlie the overdispersed population distributions of TE abundance, we developed a mathematical model of TE population genetics that includes the dynamics of element proliferation and purifying selection on TE load. The modeling approach begins with a master equation for a birth-death process and extends the predictions of the classical theory of TE dynamics in several ways. In particular, moment-based analyses of time-dependent and equilibrium population distributions of TE load reveal that overdispersion is likely to arise via copy-and-paste proliferation dynamics, especially when the elementary processes of proliferation and excision are first-order and approximately balanced. Parameter studies and analytic work confirm this result and further suggest that overdispersed population distributions of TE abundance are unlikely to be a consequence of purifying selection on total element load.

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Smith, R. D., Puzey, J., Conradi Smith, G. D.. 2020-11-17. Population genetics of transposable element load: a mechanistic account of observed overdispersion. https://doi.org/10.1101/2020.11.16.382945

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