Genetic basis of thermal plasticity variation in Drosophila melanogaster body size

Abstract

Body size is a quantitative trait that is closely associated to fitness and under the control of both genetic and environmental factors. While developmental plasticity for this and other traits is heritable and under selection, little is known about the genetic basis for variation in plasticity that can provide the raw material for its evolution. We quantified genetic variation for body size plasticity in Drosophila melanogaster by measuring thorax and abdomen length of females reared at two temperatures from a panel representing naturally segregating alleles, the Drosophila Genetic Reference Panel (DGRP). We found variation between genotypes for the levels and direction of thermal plasticity in size of both body parts. We then used a Genome-Wide Association Study (GWAS) approach to unravel the genetic basis of inter-genotype variation in body size plasticity, and used different approaches to validate selected QTLs and to explore potential pleiotropic effects. We found mostly “private QTLs”, with little overlap between the candidate loci underlying variation in plasticity for thorax versus abdomen size, for different properties of the plastic response, and for size versus size plasticity. We also found that the putative functions of plasticity QTLs were diverse and that alleles for higher plasticity were found at lower frequencies in the target population. Importantly, a number of our plasticity QTLs have been targets of selection in other populations. Our data sheds light onto the genetic basis of inter-genotype variation in size plasticity that is necessary for its evolution.

A clinal polymorphism in the insulin signaling transcription factorfoxocontributes to life-history adaptation inDrosophila

“…To isolate the two alternative foxo alleles for experiments, we used whole-genome sequenced inbred lines from the Drosophila Genetic Reference Panel (DGRP; Mackay et al 2012) to reconstitute outbred populations either fixed for the LL (G,G) and the HL (A,T) alleles. This "reconstituted or recombinant outbred population" (ROP) or "Mendelian randomization" approach produces populations that are consistently and completely fixed for the two alternative allelic states to be compared, with the rest of the genetic background being randomized (see Behrman et al [2018] and Lafuente et al [2018] for examples using this method). For each allele, we used two independent sets of DGRP lines (sets A and B for HL; sets C and D for LL; each set consisting of 20 distinct lines) and two replicate population cages per set, giving a total of eight population cages ( Fig.…”

No evidence that warmer temperatures are associated with selection for smaller body sizes

“…The reasons for the observed thermal plasticity in size, and its potential adaptive value, remain poorly understood [19][20][21][22][23]. However, if smaller body size has fitness advantages at higher temperatures, temperature-size plasticity may represent adaptive variation [22,[24][25][26][27][28]. As a result, in general, it follows that for both endotherms and ectotherms that thermal plasticity in body size may be adaptive if smaller size is favoured at warmer temperatures.…”

Multidimensional plasticity in the Glanville fritillary butterfly: larval performance curves are temperature, host and family specific

“…Such intraspecific variation, or in this case variation within the meta-population, for plasticity is common in both natural and laboratory populations [e.g. 20, 62] and hypothesised to be beneficial for insects exposed to climate change [63, 64] because it increases their evolutionary potential [24].…”

“…For example, Singh et al showed that poor host plant quality mainly influenced development at intermediate temperatures the tropical butterfly Bicyclus anynana [18]. Moreover, significant genetic variation for (multidimensional) plasticity is known to exist in both natural and laboratory populations [20-22]. This intraspecific variation in the ability to respond to an environmental cue (GxE), or combinations of cues (GxExE), is hypothesised to be beneficial in the light of climate change since it facilitates the evolution of wider ranges of environmental tolerance [23, 24].…”