THE GENETIC BASIS OF INTERSPECIFIC FEMALE PREFERENCE IN DROSOPHILA SIMULANS

Behavioral differences between species have a genetic basis and contribute to species isolation. Genomic regions have been identified that influence female rejection of heterospecific males on the right arm of the third chromosome in Drosophila, however, no individual loci have been identified. Here, I used deficiency mapping to locate regions that influence the rejection of D. melanogaster males by D. simulans females. First, I tested two genes that have been previously shown to affect female within-species mate choice: neither of these genes was found to contribute to between-species female preference. Next, 1identified five small significant regions that contain candidate genes contributing to behavioral isolation, which were all located in areas of low interspecific recombination. Furthermore, I identified the first candidate gene for behavioural isolation in Drosophila. I also provided a list of candidate gene. Identification of genes that influence behavioural isolation will provide understanding of the genetic influence on biodiversity

The second sex:Functions and mechanisms of sperm manipulation in female <i>Drosophila melanogaster</i>

Offspring production commences with mate-choice and culminates in the generation of genetically similar individuals. Males and females play distinct roles in this process: males compete to gain access to females, and females exhibit choice. When a female mates more than once, these pre-copulatory interactions extend to the female reproductive tract as sperm from multiple males compete to fertilize her eggs. To investigate the possibility that females bias sperm use after copulation, I employed the fruit fly, Drosophila melanogaster. By reviewing the literature, I found that our understanding of female post-copulatory behaviours is relatively limited and set out to investigate the mechanisms and functions of two female post-copulatory behaviours: sperm storage (movement of sperm into storage organs) and sperm ejection (removal of ejaculate). I found that females alter their attractiveness and chances of remating via ejection of sperm and anti-aphrodisiac pheromones. I also found that females who remate in quick succession produce different patterns of paternity compared to females with slower remating rates indicating an influence of the female on whose sperm is used to fertilize her eggs. To explore how this choice occurs, I artificially modified the activity of various populations of neurons and determined that sperm storage and ejection are regulated by neuronal circuits in the female central nervous system. Overall, I conclude that females’ active control over reproduction extends past pre-copulatory mate choice to include an influence on whose sperm fertilizes her eggs to produce offspring

<i>Drosophila melanogaster</i> females restore their attractiveness after mating by removing male anti-aphrodisiac pheromones

Males from many species ensure paternity by preventing their mates from copulating with other males. One mate-guarding strategy involves marking females with anti-aphrodisiac pheromones (AAPs), which reduces the females' attractiveness and dissuades other males from courting. Since females benefit from polyandry, sexual conflict theory predicts that females should develop mechanisms to counteract AAPs to achieve additional copulations, but no such mechanisms have been documented. Here we show that during copulation Drosophila melanogaster males transfer two AAPs: cis-Vaccenyl Acetate (cVA) to the females' reproductive tract, and 7-Tricosene (7-T) to the females' cuticle. A few hours after copulation, females actively eject cVA from their reproductive tract, which results in increased attractiveness and re-mating. Although 7-T remains on those females, we show that it is the combination of the two chemicals that reduces attractiveness. To our knowledge, female AAP ejection provides the first example of a female mechanism that counter-acts chemical mate-guarding

Last male sperm precedence is modulated by female remating rate in <i>Drosophila melanogaster</i>

Following multiple matings, sperm from different males compete for fertilization within the female reproductive tract. In many species, this competition results in an unequal sharing of paternity that favors the most recent mate, termed last male sperm precedence (LMSP). Much of our understanding of LMSP comes from studies in Drosophila melanogaster that focus on twice‐mated females with standardized latencies between successive matings. Despite accumulating evidence indicating that females often mate with more than two males and exhibit variation in the latency between matings, the consequences of mating rate on LMSP are poorly understood. Here, we developed a paradigm utilizing D. melanogaster in which females remated at various time intervals with either two or three transgenic males that produce fluorescent sperm (green, red, or blue). This genetic manipulation enables paternity assessment of offspring and male‐specific sperm fate examination in female reproductive tracts. We found that remating latency had no relationship with LMSP in females that mated with two males. However, LMSP was significantly reduced in thrice‐mated females with short remating intervals; coinciding with reduced last‐male sperm storage. Thus, female remating rate influences the relative share of paternity, the overall clutch paternity diversity, and ultimately the acquisition of indirect genetic benefits to potentially maximize female reproductive success

The dark side of love

Love isn't all rainbows and butterflies. Sure, in the beginning, everything is great. Everyone knows the age-old story: boy meets girl, boy courts girl, and if girl accepts then boy mates with girl. Life is good. Unfortunately, this honeymoon stage doesn't endure

The second sex: Functions and mechanisms of sperm manipulation in female Drosophila melanogaster

Offspring production commences with mate-choice and culminates in the generation of genetically similar individuals. Males and females play distinct roles in this process: males compete to gain access to females, and females exhibit choice. When a female mates more than once, these pre-copulatory interactions extend to the female reproductive tract as sperm from multiple males compete to fertilize her eggs. To investigate the possibility that females bias sperm use after copulation, I employed the fruit fly, Drosophila melanogaster. By reviewing the literature, I found that our understanding of female post-copulatory behaviours is relatively limited and set out to investigate the mechanisms and functions of two female post-copulatory behaviours: sperm storage (movement of sperm into storage organs) and sperm ejection (removal of ejaculate). I found that females alter their attractiveness and chances of remating via ejection of sperm and anti-aphrodisiac pheromones. I also found that females who remate in quick succession produce different patterns of paternity compared to females with slower remating rates indicating an influence of the female on whose sperm is used to fertilize her eggs. To explore how this choice occurs, I artificially modified the activity of various populations of neurons and determined that sperm storage and ejection are regulated by neuronal circuits in the female central nervous system. Overall, I conclude that females’ active control over reproduction extends past pre-copulatory mate choice to include an influence on whose sperm fertilizes her eggs to produce offspring

Supplementary Table 2

The courtship values and statistics for the four genotypes tested (simulans/deficiency, simulans/ Balancer, melanogaster/Deficiency, melanogaster/Balancer)

The Genetic Basis of Female Mate Preference and Species Isolation in Drosophila

The processes that underlie mate choice have long fascinated biologists. With the advent of increasingly refined genetic tools, we are now beginning to understand the genetic basis of how males and females discriminate among potential mates. One aspect of mate discrimination of particular interest is that which isolates one species from another. As behavioral isolation is thought to be the first step in speciation, and females are choosy more often than males in this regard, identifying the genetic variants that influence interspecies female mate choice can enhance our understanding of the process of speciation. Here, we review the literature on female mate choice in the most widely used model system for studies of species isolation Drosophila. Although females appear to use the same traits for both within- and between-species female mate choice, there seems to be a different genetic basis underlying these choices. Interestingly, most genomic regions that cause females to reject heterospecific males fall within areas of low recombination. Likely, candidate genes are those that act within the auditory or olfactory system, or within areas of the brain that process these systems