Abstract
Unravelling the genetic basis of adaptive traits is a major challenge in evolutionary biology. Doing so informs our understanding of evolution towards an adaptive optimum, the distribution of locus effect sizes, and the influence of genetic architecture on the evolvability of a trait. In the Müllerian co-mimics Heliconius melpomene and Heliconius erato some Mendelian loci affecting mimicry shifts are well known. However, several phenotypes in H. melpomene remain to be mapped, and the quantitative genetics of colour pattern variation has rarely been analysed. Here we use quantitative trait loci (QTL) analyses of crosses between H. melpomene races from Peru and Suriname to map, for the first time, the control of the broken band phenotype to WntA and identify a ~100 kb region controlling this variation. Additionally, we map variation in basal forewing red-orange pigmentation to a locus centred around the gene ventral veins lacking (vvl). The locus also appears to affect medial band shape variation as it was previously known to do in H. erato. This adds to the list of homologous regions controlling convergent phenotypes between these two species. Finally we show that Heliconius wing-patterning genes are strikingly pleiotropic among wing pattern traits. Our results demonstrate how genetic architecture can shape, aid and constrain adaptive evolution.
Highlights
Adaptive radiations are characterised by rapid diversification into new ecological niches and speciation
The final linkage map was constructed from 3879 SNPs across 21 linkage groups, which came to a total of 1690.833 cM. This linkage map is comparable to the 1364.23 cM of the H. melpomene genome (Davey et al 2016)
It is interesting that each of these is only found in one brood and not the other, and we suggest this may potentially be explained by epistatic interactions with the quantitative trait loci (QTL) on chromosome 18
Summary
The crossesHeliconius melpomene meriana from Victoria, Suriname (5.113892° N -54.990106° W - dennis only pattern) and H. melpomene aglaope from Schucshuyacu, Peru (−6.007558°S -75.884416° W - dennis-ray pattern) were collected and used to establish breeding stocks at the University of York. It is important to remember that these stock populations were derived from wild caught individuals who show some intra population variation which might affect the QTL found in different broods This is especially true for the Surinamese pattern that is found not far from two other Heliconius patterns (a postman and a dennis-rayed pattern). The ventral and dorsal sides of the butterfly wings were scanned using a Canon LiDE 700F scanner at 600 dpi resolution within 7 days of eclosion. This procedure avoided any coloration changes due to wear or fading.
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