RT Journal
A1 Lefébure, Tristan
A1 Morvan, Claire
A1 Malard, Florian
A1 François, Clémentine
A1 Konecny-Dupré, Lara
A1 Guéguen, Laurent
A1 Weiss-Gayet, Michèle
A1 Seguin-Orlando, Andaine
A1 Ermini, Luca
A1 Sarkissian, Clio Der
A1 Charrier, N. Pierre
A1 Eme, David
A1 Mermillod-Blondin, Florian
A1 Duret, Laurent
A1 Vieira, Cristina
A1 Orlando, Ludovic
A1 Douady, Christophe Jean
T1 Less effective selection leads to larger genomes
JF Genome Research 
JO Genome Research 
YR 2017 
FD June 01 
VO 27 
IS 6 
SP 1016 
OP 1028 
DO 10.1101/gr.212589.116 
UL http://genome.cshlp.org/content/27/6/1016.abstract 
AB The evolutionary origin of the striking genome size variations found in eukaryotes remains enigmatic. The effective size of populations, by controlling selection efficacy, is expected to be a key parameter underlying genome size evolution. However, this hypothesis has proved difficult to investigate using empirical data sets. Here, we tested this hypothesis using 22 de novo transcriptomes and low-coverage genomes of asellid isopods, which represent 11 independent habitat shifts from surface water to resource-poor groundwater. We show that these habitat shifts are associated with higher transcriptome-wide . After ruling out the role of positive selection and pseudogenization, we show that these transcriptome-wide  increases are the consequence of a reduction in selection efficacy imposed by the smaller effective population size of subterranean species. This reduction is paralleled by an important increase in genome size (25% increase on average), an increase also confirmed in subterranean decapods and mollusks. We also control for an adaptive impact of genome size on life history traits but find no correlation between body size, or growth rate, and genome size. We show instead that the independent increases in genome size measured in subterranean isopods are the direct consequence of increasing invasion rates by repeat elements, which are less efficiently purged out by purifying selection. Contrary to selection efficacy, polymorphism is not correlated to genome size. We propose that recent demographic fluctuations and the difficulty of observing polymorphism variation in polymorphism-poor species can obfuscate the link between effective population size and genome size when polymorphism data are used alone.