Innovative mark-recapture experiment shows patterns of selection on
transcript abundance in the wild
A fundamental aspect of evolutionary biology is natural selection on
trait variation. Classically, selection has been estimated primarily on
external morphological traits such as beak size and coloration, or on
easily-assayable physiological traits such as heat-tolerance. As
technologies and methods improved, evolutionary biologists began
examining selection on molecular traits such as protein sequences and
cellular processes. In a From the Cover manuscript in this issue of
Molecular Ecology, Ahmad et al. (2021) continue this trend by estimating
parasite driven selection on the molecular trait of transcript abundance
in a wild population of brown trout (Salmo trutta) by uniquely combining
a mark-recapture experimental design with non-invasive RNA sampling.
Using transcript abundance to estimate selection allows for many
different traits (each unique gene’s transcript counts) to be tested in
a single experiment, providing the opportunity to examine trends in
selection. Ahmad et al.(2021) find directional selection strength on
transcript counts is generally low and normally distributed.
Surprisingly, transcripts under non-linear selection showed a disruptive
selection bias contradicting previous comparative studies and
theoretical work. This highlights the importance of within-generation
selection studies, where mechanisms may differ from longer time frames.
Their manuscript also highlights the benefits of an improved 3’ RNA
sequencing technique to measure gene expression.