How are mate preferences and sexual traits encoded in the genome?
How do processes of genome evolution shape reproductive behaviors?
To answer these questions we study several of the closely related fishes in the family Poecilidae. Mate choice and reproductive traits have evolved rapidly across these species, allowing us to couple comparative and mechanistic approaches.
How do relatively small Y chromosomes control expression of the rest of the genome?
Males and females differ dramatically in physiology and behaviour, yet they share the majority of their genomes, differing only by the presence of a Y chromosome in males. Yet Y chromosomes are frequently quite small and contain few genes.
What are the evolutionary pressures and processes that generate diversity in non-recombining regions of a genome?
Recombination is the process that mixes together the genes from a mother and father, and plays an important role in generating diversity while removing deleterious mutations. However, some regions of the genome never recombine (such as Y chromosomes).
Males of the species Poecilia parae are always one of five discrete morphs that utilizes different complex reproductive strategies; differing dramatically by color, body size, and courtship behavior. We previously found there are five different Y chromosomes in this one species, which control all the male traits together. We are taking advantage of this unique system to answer the above broad questions of genome evolution.
To what extent are differences in preference determined by peripheral versus central sensory processing?
Sensory systems (eg. vision) detect stimuli in the environment and send signals to the brain for central processing. But sensory systems can be tuned to differentially detect signals before they reach the brain; for example the wavelengths of light detected for color vision is determined in the eye.
The bodies of male guppies (Poecilia reticulata) all have unique combinations of color patterns. Female preference for male color patterns varies by environment and appears to be influenced by gene expression both in the brain and in the eyes.
How are complex reproductive strategies genetically determined?
Reproductive strategies are based on complex phenotypes that rely on having the correct combination of coloration, morphology, and behavior. Such complex strategies either require multiple genes or tissue specific gene activity.
Across Poeciliid fishes there are several male reproductive strategies with corresponding differences in male coloration and behavior. In addition to P. parae , males of P. reticulata and P. picta choose to use one of two strategies when attempting to mate with a female; either they display for her, or they attempt to force copulate. While the later looks the same in all three species, the display behaviors differ dramatically; with male P. reticulata wiggling in front of females, while P. picta swims rapid circles around the female's head.