John Fitzpatrick

John Fitzpatrick

Assistant Professor, Docent

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Works at Department of Zoology
Telephone 08-16 26 21
Visiting address Svante Arrhenius väg 18b
Room D 541
Postal address Zoologiska institutionen: Etologi 106 91 Stockholm

About me

Why are reproductive behaviours so variable among animals? How do animals compete for mating opportunities? And how do animals choose their mates? 

My lab examines all of these questions by focusing on sexual selection and the evolution of reproductive behaviours. Research in my lab primarily aims to develop an integrated understanding of how sexual selection shapes the evolution of reproductive behaviours. To do this we investigate male-male competition before and after mating, female mate choice before and after mating, the evolution of sexual weapons and ornaments, trade-offs among sexually selected traits, and co-evolutionary dynamics beteween the sexes. We combine experimental and phylogenetic comparative approaches and focuses on a wide range of animals, ranging from fish to humans.  



Research in my group is currently focused on:



When it comes to sex you can’t have it all. Animals must balance their investment in behaviours and traits important before and after mating. My lab tries to understand how animals balance the competing demands of sex. We address this question experimentally in the lab using halfbeak fishes as a model. Halfbeaks are small, live-bearing freshwater fish from Southeast Asia that are easy to keep and breed in the lab. These fish show overt competitive behaviours, display sexual ornaments and multiple mating is common, making them an ideal model for assessing trade-offs among sexually selected traits. 



Females mate with multiple males in most animal species, which has important evolutionary consequences. We are using phylogenetic comparative analyses to explore how variation in female promiscuity influences the evolution of male sexual behaviours and traits. This work focuses on sharks and rays, bony fish, social insects, marine mammals, and mammals generally. We explore how co-evolutionary dynamics between males and females influence the evolution of testes, sperm, genitals and female remating rates and assess trade-offs at the macroevolutionary scale.



Competition and choice for reproductive opportunities doesn't end at mating. Our lab focuses on how sperm compeition shapes sperm behaviour, how sperm respond to chemoattractants released by the eggs (or surrounding cells), and how sperm-female interactions influence sperm behaviour. This work spans the animal tree of life, including work on marine invertebrates, fish and humans. 



Animals display an enormous variation in colouration and patterns, which is shaped by both natural and sexual selection. Our lab examines both of these selective forces to gain a better understanding of why animals look the way they do. We combine phylogenetic comparative studies with experimental approahces using our lab populations of bamboo sharks and halfbeak fish. 



2014-2018: Editor for Behavioral Ecology 
2011-2015: Board of Reviewing Editors for Journal of Evolutionary Biology



Postdoctoral Researchers

     Alessandro Devigili

     Ariel Kahrl

     Raissa de Boer

PhD Students

     Charel Reuland

     Madicken Åkerman

     Erika Fernlund Isaksson


     Amy Rowley

     Hannah Ogden




For a complete list of publications plase see my Google Scholar page.


Amy Rowley publishes the second chapter from her PhD thesis in the Journal of Evolutionary Biology. Getting your hands on shark sperm can be challenging. Luckily we were able to work with a fantastic multinational team!


In a new paper published in Proceeding B, Alessandro Devigili, Jon Evans and I explore the complicated ways that predation shapes how ejaculate traits evolve. 


In a new paper published in Nature Communications, Leigh Simmons and I show that female genitalia evolve rapidly in dung beetles - evolving even faster than male genitalia!


Amy Rowley published her first chapter from her PhD thesis in Behavioral Ecology! This work looked at sharks and bony fish and demonstred a convergent response to sperm competition: namely, when females mate with multiple males, males investment more in sperm number. 


Hannah Ogden published some of the amazing pictures she took during her MSc projct showing the variation in the abdominal spot in female halfbeaks. These photos were published as part of Molecular Reproduction & Development's "VISION: the art of science" series. Hannah even managed to get a photo of an unborn offspring looking out of a female's abdominal spot (check out the white arrow below)! 



Alessandro Devigili leads in our effort to examine how sperm-female interactions influence reproductive barriers in this article published in the Journal of Evolutionary Biology.


Leigh Simmons, Stefan Lüpold and I explore the world of evolutionary trade-offs among sexual traits in animals in a new paper published in TREE.


Cody Dey leads a multinational team to evaluate why fish evolve complex cooperative behaviours in an article published in Nature Ecology and Evolution.





A selection from Stockholm University publication database
  • 2016. Leigh W. Simmons, John L. Fitzpatrick. Evolution 70 (5), 998-1008

    Reproductive competition generates episodes of both pre- and postcopulatory sexual selection. Theoretical models of sperm competition predict that as the fitness gains from expenditure on the weapons of male combat increase, males should increase their expenditure on weapons and decrease their expenditure on traits that contribute to competitive fertilization success. Although traits subject to sexual selection are known to have accelerated evolutionary rates of phenotypic divergence, it is not known whether the competing demands of investment into pre- and postcopulatory traits affect their relative rates of evolutionary divergence. We use a comparative approach to estimate the rates of divergence in pre-and postcopulatory traits among onthophagine dung beetles. Weapons evolved faster than body size while testes mass and sperm length evolved more slowly than body size, suggesting that precopulatory competition is the stronger episode of sexual selection acting on these beetles. Although horns evolved faster than testes, evolutionary increases in horn length were not associated with evolutionary reductions in testes mass. Our data for onthophagines support the notion that in taxa where males are unable to monopolize paternity, expenditure on both weapons and testes should both be favored.

  • 2014. Stefan Lüpold (et al.). Nature Communications 5

    Theory predicts a trade-off between investments in precopulatory (ornaments and armaments) and postcopulatory (testes and ejaculates) sexual traits due to the costs associated with their growth and maintenance within the finite energy resources available. Empirical studies, however, have revealed considerable inconsistency in the strength and direction of relationships among these sexual traits. Ambiguity may result from variance in the marginal benefits gained by increasing investments in either pre- or postcopulatory sexual traits. Here, in a broad comparative study, we test the prediction that the relationship between pre- and postcopulatory sexual traits differs among taxa relative to the importance of male-male contest competition within them. We find that covariance between pre- and postcopulatory sexual traits gradually shifts from strongly positive to strongly negative with increasing male-male contest competition. Thus, our findings reveal a potentially unifying explanation for the oftentimes inconsistent relationships in the strength and direction of covariance among sexual traits.

  • 2009. John L. Fitzpatrick (et al.). Proceedings of the National Academy of Sciences of the United States of America 106 (4), 1128-1132

    Sperm competition, the contest among ejaculates from rival males to fertilize ova of a female, is a common and powerful evolutionary force influencing ejaculate traits. During competitive interactions between ejaculates, longer and faster spermatozoa are expected to have an edge; however, to date, there has been mixed support for this key prediction from sperm competition theory. Here, we use the spectacular radiation of cichlid fishes from Lake Tanganyika to examine sperm characteristics in 29 closely related species. We provide phylogenetically robust evidence that species experiencing greater levels of sperm competition have faster-swimming sperm. We also show that sperm competition selects for increases in the number, size, and longevity of spermatozoa in the ejaculate of a male, and, contrary to expectations from theory, we find no evidence of trade-offs among sperm traits in an interspecific analysis. Also, sperm swimming speed is positively correlated with sperm length among, but not within, species. These different responses to sperm competition at intra-and interspecific levels provide a simple, powerful explanation for equivocal results from previous studies. Using phylogenetic analyses, we also reconstructed the probable evolutionary route of trait evolution in this taxon, and show that, in response to increases in the magnitude of sperm competition, the evolution of sperm traits in this clade began with the evolution of faster (thus, more competitive) sperm.

Show all publications by John Fitzpatrick at Stockholm University

Last updated: August 25, 2020

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