Comparison between phenotypic variances over mutant and control backgrounds.

<p>Comparison between phenotypic variances over mutant and control backgrounds.</p

QTLs identified in previous studies associated to the candidate genes tested in this work.

<p>QTLs identified in previous studies associated to the candidate genes tested in this work.</p

Map showing the collection sites.

<p>Localities were adults of <i>Drosophila melanogaster</i> were collected.</p

Natural Genetic Variation and Candidate Genes for Morphological Traits in <i>Drosophila melanogaster</i>

<div><p>Body size is a complex character associated to several fitness related traits that vary within and between species as a consequence of environmental and genetic factors. Latitudinal and altitudinal clines for different morphological traits have been described in several species of <i>Drosophila</i> and previous work identified genomic regions associated with such variation in <i>D</i>. <i>melanogaster</i>. However, the genetic factors that orchestrate morphological variation have been barely studied. Here, our main objective was to investigate genetic variation for different morphological traits associated to the second chromosome in natural populations of <i>D</i>. <i>melanogaster</i> along latitudinal and altitudinal gradients in Argentina. Our results revealed weak clinal signals and a strong population effect on morphological variation. Moreover, most pairwise comparisons between populations were significant. Our study also showed important within-population genetic variation, which must be associated to the second chromosome, as the lines are otherwise genetically identical. Next, we examined the contribution of different candidate genes to natural variation for these traits. We performed quantitative complementation tests using a battery of lines bearing mutated alleles at candidate genes located in the second chromosome and six second chromosome substitution lines derived from natural populations which exhibited divergent phenotypes. Results of complementation tests revealed that natural variation at all candidate genes studied, <i>invected</i>, <i>Fasciclin 3</i>, <i>toucan</i>, <i>Reticulon-like1</i>, <i>jing</i> and <i>CG14478</i>, affects the studied characters, suggesting that they are Quantitative Trait Genes for morphological traits. Finally, the phenotypic patterns observed suggest that different alleles of each gene might contribute to natural variation for morphological traits. However, non-additive effects cannot be ruled out, as wild-derived strains differ at myriads of second chromosome loci that may interact epistatically with mutant alleles.</p></div

Quantitative Complementation Tests for body size related traits.

<p>Mean values of body size traits (Face Width, Head Width, Thorax Length and Wing Size) corresponding to individuals derived from complementation tests between second chromosome substitution lines (Chilecito 29, Jáchal 5, Lavalle 12, Neuquén 58, San Blas 29 and Güemes 269) and the laboratory lines (mutant and control lines) averaged across sexes. Crosses with substitution lines which had previously shown larger and smaller sizes are indicated in green and red respectively. <i>inv</i> (<i>invected</i>), <i>Fas 3</i> (<i>Fasciclin 3</i>), <i>toc</i> (<i>toucan</i>), <i>Rtnl1</i> (<i>Reticulon-like1</i>), <i>jing</i> and <i>CG14478</i> are the candidate genes affected by the <i>P</i>-element insertion in the mutant strains used. The control is a <i>P</i>-element free insertion line with the same genetic background than the rest of the strains used.</p

Within-population quantitative genetic analyses for morphological traits.

<p>Within-population quantitative genetic analyses for morphological traits.</p

Genetic complementation tests for morphological traits.

<p>Genetic complementation tests for morphological traits.</p

Lines showing significant effects for each trait, temperature and sex.

<p>Number of mutant lines showing significant differences with respect to the control for each morphological trait. We enumerated the lines showing significant effects at 17°C (blue circles), at 25°C (pink circles) and at both temperatures simultaneously (intersections between blue and pink circles). Also, for each one of the mentioned categories, we enumerated the lines showing significant effects only in males (M), only in females (F) and in both sexes simultanously (M&F).</p

Lines showing phenotypic plasticity for different traits in each sex.

<p>Number of lines showing phenotypic plasticity for one, two, three, four or all five traits in females (F) and males (M). FW: Face Width, HW: Head Width, TL: Thorax Length, WSi: Wing Size and WSh: Wing Shape. The candidate genes (or the name of the lines when the respective genes could not be identified) affecting plasticity of a large number of traits in each sex are: ^a<i>Drak</i>; ^b<i>rut</i>; ^c BG00930, <i>CG13333</i>, <i>CG13334</i>; ^d BG02239; ^e<i>Btk29A</i>; ^f<i>CG43340</i>, <i>Drak</i>, <i>jim</i>.</p

Genotype by environment interaction for each body size related trait in females.

<p>Line by temperature interaction in females for A) Face Width, B) Head Width, C) Thorax Length and D) Wing Size. Each dot corresponds to the average of the transformed values. <i>V_GEI</i> (R) is the percentage of GEI’s variance explained by changes in ranking order. The three lines showing the largest significant differences between temperatures are coloured.</p