Are the same genes responsible for intra- and interspecific variability for sex comb tooth number in Drosophila?

Abstract

The identification of genes contributing to speciation has the potential to provide important insights into the mechanisms of evolution. One of the most interesting unresolved puzzles is the relationship between intraspecific variability in morphological traits and their interspecific divergence. Intraspecific polymorphisms without major detrimental side-effects may serve as a substrate for selection response during speciation. The same quantitative trait loci (QTLs) may, then, account for the trait variability both within and between species. In contrast, the vast majority of intraspecific variants could be deleterious mutations that have not yet been selected out. In this case intraspecific variation would not ultimately generate interspecific trait differences. In previous work, QTLs responsible for morphological differences between animal species, including those for the secondary sexual trait sex comb tooth number, have been mapped with the resolution of chromosome segments. Here, we mapped QTLs for which alleles segregated between two laboratory lines of Drosophila melanogaster. The two QTLs identified mapped to the X chromosome and accounted for only 8% of the between-line differences, implying that a large number of small-effect genes modify sex combs. One intraspecific QTL mapped to the same interval as the QTL for interspecific differences between D. simulans and D. mauritiana. Whether or not these effects result from the same genes requires further examination.

Quantitative trait loci affecting a courtship signal in Drosophila melanogaster

“…The use of RI lines derived from parental strains that are not significantly different for the trait in question, has been quite successful in D. melanogaster. The same RI lines used here have been used in QTL studies of life history and morphological traits, which typically show limited interspecific variation, including longevity (Nuzhdin et al, 1997;Vieira et al, 2000), bristle number (Gurganus et al, 1998), reproductive success Wayne et al, 2001), sex combs (Nuzhdin and Reiwitch, 2000) and ovariole number (Wayne et al, 2001). We ask if the RI lines vary significantly in mean IPI and analyse the genetic basis of this variation.…”

Variation and Evolution of Male Sex Combs in Drosophila: Nature of Selection Response and Theories of Genetic Variation for Sexual Traits

“…Previous studies have investigated sex comb bristle number variation within and between species of the melanogaster complex using quantitative trait loci (QTL) mapping and gene expression analyses (Coyne 1985;True et al 1997;Macdonald and Goldstein 1999;Nuzhdin and Reiwitch 2000;Kopp et al 2003;Tatsuta and Takano-Shimizu 2006;Graze et al 2007). Despite a large amount of work in this field, there remains a gap in our basic understanding of sex comb bristle number inheritance and evolution.…”

Quantitative Trait Loci for Aggressive Behavior inDrosophila melanogaster

“…Recombinant inbred lines (RILs) derived from these strains have been used previously to map QTL affecting a wide variety of quantitative traits: life span (Nuzhdin et al 1997;Leips and Mackay 2000;Pasyukova et al 2000;Vieira et al 2000;Leips and Mackay 2002;Reiwitch and Nuzhdin 2002;Lai et al 2007); starvation Harbison et al 2004); heat and cold stress resistance ; reproductive success Wayne et al 2001); numbers of sensory bristles (Gurganus et al 1998); sex comb teeth (Nuzhdin and Reiwitch 2000) and ovarioles (Wayne et al 2001); flight velocity and metabolic traits (Montooth et al 2003); courtship song (Gleason et al 2002); and olfactory (Fanara et al 2002), male mating (Moehring and Mackay 2004), and locomotor ( Jordan et al 2006) behavior. We used a population of introgression lines derived from the recombinant inbred lines to map QTL affecting aggressive behavior.…”