DOI: 10.5061/dryad.c27gd83
title: Data from: Y-chromosomes can constrain adaptive evolution via epistatic interactions with other chromosomes

description: Background: Variation in the non-coding regions of Y-chromosomes have been
 shown to influence gene regulation throughout the genome in some systems;
 a phenomenon termed Y-linked regulatory variation (YRV). This type of
 sex-specific genetic variance could have important implications for the
 evolution of male and female traits. If YRV contributes to the additive
 genetic variation of an autosomally coded trait shared between the sexes
 (e.g. body size), then selection could facilitate sexually dimorphic
 evolution via the Y-chromosome. In contrast, if YRV is entirely
 non-additive (i.e. interacts epistatically with other chromosomes), then
 Y-chromosomes could constrain trait evolution in both sexes whenever they
 are selected for the same trait value. The ability for this phenomenon to
 influence such fundamental evolutionary dynamics remains unexplored.
 Results: Here we address the evolutionary contribution of Y-linked
 variance by selecting for improved male geotaxis in populations possessing
 multiple Y-chromosomes (i.e. possessed Y-linked additive and/or epistatic
 variation) or a single Y-chromosome variant (i.e. possessed no Y-linked
 variation). We found that males from populations possessing Y-linked
 variation did not significantly respond to selection; however, males from
 populations with no Y-linked variation did respond. These patterns suggest
 the presence of a large quantity of Y-linked epistatic variance in the
 multi-Y population that dramatically slowed its response. Conclusions: Our
 results imply that YRV is unlikely to facilitate the evolution of sexually
 dimorphic traits (at least for the trait examined here), but can interfere
 with the rate of trait evolution in both males and females. This result
 could have real biological implications as it suggests that YRV can affect
 how quickly a population responds to new selective pressures (e.g.
 invasive species, novel pathogens, or climate change). Considering that
 YRV influences hundreds of genes and is likely typical of other
 independently-evolved hemizygous chromosomes, YRV-like phenomena may
 represent common and significant costs to hemizygous sex determination.
description: Geotaxis measurements
 for flies from Y-chromosome diversity treatmentsGeotaxis behavior was
 measured using constructed PVC mazes in a controlled laboratory
 environment where flies were forced to make a series of up/down climbing
 decisions. Flies have unique individual ID's. The day that the
 assessment was run is indicated by a categorical numeric value.
 Y-chromosome diversity treatment is indicated by either 1 or 25.
 Experimental populations are identified by a value indicating the
 Y-chromosome diversity treatment (1 or 25) followed by a decimal point and
 the unique replicate population ID within each diversity treatment (1-3).
 Males and females are differentiated by lowercase m or f respectively.
 Scores for individual flies range from 0-6 (0 represents the most
 positively geotactic and 6 represents the most negatively geotactic
 behaviors). Populations were assessed across multiple mazes identified by
 a unique ID name. Populations were assessed before selection and after
 selection indicated by generation values 0 or 16
 respectively.Kutch and Fedorka - Y epistasis
 constraint data.xlsx