Abstract
To gain insight into the molecular genetic basis of standing variation in fitness related traits, we identify a novel factor that regulates the molecular and physiological basis of natural variation in female Drosophila melanogaster fecundity. Genetic variation in female fecundity in flies derived from a wild orchard population is heritable and largely independent of other measured life history traits. We map a portion of this variation to a single QTL and then use deficiency mapping to further refine this QTL to 5 candidate genes. Ubiquitous expression of RNAi against only one of these genes, an aquaporin encoded by Drip, reduces fecundity. Within our mapping population Drip mRNA level in the head, but not other tissues, is positively correlated with fecundity. We localize Drip expression to a small population of corazonin producing neurons located in the dorsolateral posterior compartments of the protocerebrum. Expression of Drip–RNAi using both the pan-neuronal ELAV-Gal4 and the Crz-Gal4 drivers reduces fecundity. Low-fecundity RILs have decreased Crz expression and increased expression of pale, the enzyme encoding the rate-limiting step in the production of dopamine, a modulator of insect life histories. Taken together these data suggest that natural variation in Drip expression in the corazonin producing neurons contributes to standing variation in fitness by altering the concentration of two neurohormones.
Highlights
The life history of an organism—its reproductive schedule and lifespan—are fundamental characteristics intrinsically related to its evolutionary fitness
In Arabidopsis thaliana genetic variation in reproductive timing in response to vernalization has been mapped to polymorphisms in FLOWERING LOCUS C [9,10] and FRIGIDA [11]
A major goal of modern evolutionary biology is to elucidate the genetic basis of standing genetic variation underlying fitness traits
Summary
The life history of an organism—its reproductive schedule and lifespan—are fundamental characteristics intrinsically related to its evolutionary fitness. Natural genetic variation in only two genes has been associated with variation in fecundity (mth and InR; [33,34]) several studies have identified positional QTL for age specific female fecundity [35], male mating success [36] and ovariole number [37,38] without resolving a molecular or specific genetic determinant. To advance this issue we identify novel genetic loci
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