SEARCH

 

Chris Holland
Ph.D. Candidate

Chris Holland

Department of Biology
Texas A&M University 

3258 TAMU
College Station, TX 77843 

Tel: 979.845.3614 

email:cholland@bio.tamu.edu 

Curriculum Vitae (updated April 2018)

Chris Holland

I graduated from the University of Rhode Island with a B.S in Animal Pre-veterinary Science and minors in Marine Biology and Psychology. At URI, I worked in Dr. Jacqueline Webb’s Lab on an independent project that looked at communication and sensory biology in two species of cichlid fishes. I wanted to see how behaviors in these two species are mediated by sensory input by measuring their respective contribution to communication.

I joined the Rosenthal lab in 2014 and continued to work on sensory systems and their contribution to the evolution of behavioral communication. My project’s aim is to better understand a key component of male sexual signals, the use of pheromones in communication. Specifically, I investigate how two naturally hybridizing species of Xiphophorus use chemical communication, what the mechanisms of control are, and what the signal's chemical composition is. Identifying the compounds in this model system will enable me to explore the diversity of signals that exist: between species, between intraspecific populations, and within populations which will provide insight to a possible mechanism for speciation and further our understating of how male signals impact female mate choice and correlated effects on reproductive isolation.

To date my work has focused on interspecific differences between the sympatric X. birchmanni and X. malinche, which form natural hybrid zones as a consequence of changes in water chemistry. I showed that pheromones are produced in the testis, and used solid phase extraction (SPE) preparation in combination with high performance liquid chromatography / mass spectrometry (HPLC/MS) to characterize pheromone chemical composition. Analysis of reconstituted eluates with HPLC showed four distinct peaks shared between birchmanni and malinche, and two peaks unique to birchmanni (figure 1). Peaks 1-4 showed the same retention times and m/z patterns between species between samples and replicated of both species. By contrast, fractions A and B were found only in X. birchmanni. Isolation of fractions A & B was achieved from elution and verified with HPLC. Experimental manipulation of signal structure showed that the presence of these components is critical to conspecific mate recognition by X. birchmanni.

Figure 1

I am now seeking to understand the role genotype plays in hybrids male pheromone production. If pheromones play a role in reproductive isolation, pheromone profiles should map on to male genotypes. Natural hybrid zones vary from highly structured, with distinct, assortatively mating birchmanni-like and malinche-like subpopulations, to highly admixed hybrid swarms. Analysis of individual male pheromone profiles allows us to test the prediction that pheromones mediate assortative mating in structured hybrid populations.

This is one of the first studies in a vertebrate to characterize the chemical signals involved in reproductive isolation and demonstrate that pheromonal communication between senders and receivers constitutes a key mechanism of reproductive isolation.

When not playing Dr. Dolittle, I enjoy crossfit, yoga, hiking, swimming, eating inhuman amounts of vegetarian food, and being outside with my dogs.

Publications

  1. M. Schumer, C. Xu, D.L. Powell, A. Durvasula, L. Skov, C. Holland, J. C. Blazier, S. Sankararaman,P. Andolfatto, G.G. Rosenthal and M. Przeworski, 2018. Natural selection interacts with the local recombination rate to shape the evolution of hybrid genomes. Science. aar3684. [PDF]
  2. Z. Baker, M. Schumer, Y. Haba, L. Bashkirova, C. Holland, G.G. Rosenthal and M. Przeworski, 2017. Repeated losses of PRDM9-directed recombination despite the conservation of PRDM9 across vertebrates. eLife. doi: 10.7554/eLife.24133. [PDF]