Research

Research in my lab focuses on the evolution of mating preferences and mate choices. By transcending boundaries of field-based behavioral ecology and lab-based quantitative genetics and genomics, we aim to answer fundamental questions about evolution and genomics of mating preferences that will eventually help us causally link selective forces in real natural populations to variation in mating preferences to the underlying genetic, epigenetic, and genomic mechanisms.
 
Three panels. Left Panel: Cricket standing on a leaf with a hole in it the size of the cricket. Middle Panel: Cricket on a leaf in the shaded part as other large leaves are around. Right Panel: Mingzi Xu reaching into a copse of tropical trees with a long stick and holding a large net underneath

 

Study system

We use crickets as our model system in studying mating preferences. In the genus Gryllus, both male song and female acoustic preference have diverged repeatedly among lineages but remained coordinated within a lineage, resulting in species-specific mating signals. Sexual selection is thought to be a driver of speciation in this genus. With a reference genome available and the ability to be maintained in the lab, the crickets provide an ideal context to study the genomic basis of mating preferences. There is a lot know about the neurological basis of both singing and song discrimination in Gryllus crickets, offering a candidate to perform targeted genetic, epigenetic, and genomic probing guided by neurobiology. As a locally available system, the Gryllus crickets also offers an opportunity to conduct long term field behavioral and ecological experiments. 

Genetic basis for signal-preference coevolution

Divergence of mating preferences is ultimately a coevolutionary problem: while preference and the preferred trait can each diverge among lineages, they must remain coordinated within a lineage for mating to occur. As preference and sexual trait are often different types of traits involving distinct systems and developmental pathways, what genetic and genomic mechanisms enable preferences and preferred traits to evolve in coordination? My past research in Dr. Kerry Shaw's lab at Cornell University has focused on testing hypotheses on the genetic architecture underlying song-preference coevolution in the Laupala crickets. Our data offered strong evidence for genetic coupling (a shared pleiotropic gene or tightly linked genes) and highlighted an important role it plays in mediating signal-preference coevolution (Xu and Shaw 2019a, 2019b, 2021). Through annotation of targeted genomic regions, we have also identified a list of candidate genes for variation in both male singing and female preference. 
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Future research in this direction will seek to use behavioral experiments and functional genomics to validate candidate genes in collaboration with the Shaw lab at Cornell university. In addition, we will leverage the power of neurobiology in collaboration with neuroethologists in the Gryllus crickets to pinpoint neurogenetic basis of responses to different male songs. 
Figure with a drawing of a male cricket with a microphone with arrow pointing to two different graphs showing the pulse rate is different between the two species: L. paranigra and L. kohalensis. Below that is a symbol for female with a diagram with multiple tubes with speaker on other sides. At bottom is diagram of one tube to show how preference for sound is determined by position of female in tube
from Xu & Shaw 2019 Proc B

Variation, evolution, and genetics of choosiness

Variation in how choosy choosers are is common. A female cricket may mate with most males it visits whereas another female may reject most males. In Pride and Prejudice, whereas Elizabeth is picky among her male suitors, Charlotte was ready to marry the first man who comes her way. Where does such variation come from? What is the general pattern of variation? Can such variation be subjected to selection? What are the proximate mechanisms for this variation? What are the effects of variation on trait evolution and speciation?
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This research program aims to answer these questions by combining field and lab based behavioral experiments, quantitative genetics, differential gene expression, QTL mapping, and functional genomics, offering a rich context for students to learn skills and design related independent projects.​
 

Sexual selection and acoustic communication in a changing world

Human activities are changing the world animals live in rapidly. It is becoming increasingly difficult to find the so-called pristine habitat that has not been altered by human activities in some ways. Artificial lights, noises, chemical pollutants, man-made structures, and heat we generate all represent new realities for animals. What do these mean for animals? How do human activities affect sexual communication and mate choice? Where is sexual selection headed in this changing world?
 
We are interested in answering some of the questions using the Gryllus crickets as a study system. A few topics we are currently interested in are:

  • How do chemical pollutants such as insecticide residues affect singing, song preference, and reproductive barrier of cricket species?
  • How do man-made structures in urban areas affect sound propagation and sound localization? And does the effect translate to plasticity or adaptation in singing or phonotaxis behavior of crickets living in the city?
  • What are the evolutionary consequences of the behavioral changes in natural population?

 

Three panels. Left Panel: Computer and monitor with a plush grasshopper sitting on the monitor. Sound equipment seen in background. Middle Panel: Outside view of sound chamber. Right Panel: Inside the sound chamber with foam panels around wall and an arena in the middle.