Niclas Kolm, Assistant Professor



Dept. of Ecology and Evolution/Animal Ecology
Norbyv. 18d
SE-752 36 Uppsala

+46 (0)18 471 2639

+46 (0)18 471 6484


Research interests

My general interests lie in the fields of Evolutionary Biology and Behavioural Ecology. I mainly use fishes as model organisms to investigate the causes and consequences of the enormous diversity in morphology, life-histories and behaviour that we find among animals at the levels of individuals, populations and species. The tools I use range from field observations to controlled lab experiments and comparative analyses.

Currently I focus on three main areas of research:

1. Sensory exploitation and the evolution of animal signal/receiver systems

In this project, I investigate the evolution of Sensory Exploitation and its implications as a starting point for the evolution of signal-receiver interactions in a mate choice context. This work is based on field studies and lab experiments on a remarkable species of fish, Corynopoma riisei, a Trinidadian Characid. In this species, the male carries a paddle-like structure growing from the operculum on each side of the body. At the end of each paddle there is a flag-like appendix. During courtship, males wave these paddles in front of a female who (believing it is a food item) bites at the flag-like structure and thus positions herself so that the male can insert a sperm package into the female with lighting speed. The female can then store this sperm package for an extended period of several months and use it to fertilise several batches of eggs. Moreover, the male has three different pairs of pheromone glands (one near the tail, one on the gills and one near the pelvic fin) that he evidently uses during courtship. Using this species, I investigate, in collaboration with Mirjam Amcoff, PhD-student in my lab, and Göran Arnqvist, the following questions:

-What are the fitness consequences for females from responding to sensory exploitation?

-Can sexual selection through sensory exploitation lead to populations diverging and hence speciation?

-What scenarios drive the evolution of multiple sexually selected traits in males?

-What are the causes and consequences of laterality in male sexual signalling?

-What are the costs of carrying extreme sexual signals?

-What are the effects of male courtship pheromones on females?

Male C. riisei

The C. riisei lab at EBC

Field collection of C. riisei with Göran Arnqvist

2. Evolution of parental care patterns, sexual dimorphism, life histories, body size and brain structure in cichlid fishes

In all these traits, the cichlid fishes display an enormous variation. I use formal comparative analyses to investigate (within the correlative frame-work of such analyses) the adaptive reasons for this variation and also the links between the various aspects of the ecology of these species. Together with Alejandro Gonzalez Voyer, Wenner-Gren Foundations funded post-doc in my lab, and collaborator Svante Winberg, I focus mainly on the following questions:

-What are the causes of variation in parental care patterns in cichlid fishes?

-What factors have driven the link between sexual selection and parental care patterns in this group of fishes?

-What are the evolutionary patterns of brain size and brain structure in the Tanganyikan group of cichlids?

-What are the causes of variation in brain size and brain structure among the sexes and species in this group?

-Is there any link between brain structure and speciation patterns in Tanganyikan cichlids?

-Are there trade-offs between the different regions of the vertebrate brain?

-What are the causes of sexual size dimorphism in this group? And what are the relationships between different aspects of sexual selection (e.g. sexual size dimorphism, sexual dichromatism, mating system, sexual morphological dimorphism) in this group?

3. Variation in brain structure among individuals with different life-history strategies within a wild population of brown trout

Almost nothing is known about the intra-specific variation in brain structure among vertebrates. For this project I investigate, in collaboration with Svante Winberg, Daniel Brelin and Claes Dellefors, differences in brain structure among different mating strategies of brown trout from river Jörlanda in Gothenburg.

Hard at work, actively standing next to a bucket, at river Jörlanda. Claes Dellefors, Sweden's most skilled electrofisher, is exercising his craft in the background

Previous (but far from buried!) interests

During my PhD (supervised by Anders Berglund and Ben Sheldon) I investigated mutual mate choice, size assortative mating, differential allocation, group stability, information contents in female courtship behaviours, population biology and conservation biology using the Banggai cardinalfish as a model. These studies enabled me to start up collaborations with for instance Eric Hoffman and Jens Olsson. Given the extreme ease with which one can perform controlled field experiments on this species (the species form highly stable group structures at only 2 metres depth), I aim to continue some of these investigations in the future.

Female Banggai cardinalfish (lower specimen) courting a male

Field observations of the Banggai cardinalfish in the field at Sulawesi, Indonesia

During my post-docs at UEA and Edinburgh University I started getting interested in investigating life-history evolution using comparative methods. Together with Nick Goodwin and John Reynolds I got into comparative analyses on the cichlid system at UEA. This was later followed by a comparative study on Galliform birds in collaboration with Emma Cunningham, Will Stein and Arne Mooers while in Edinburgh. Brent Emerson at UEA also got me interested in large-scale analyses of what factors causes diversification, a collaboration that continues today.



41. Amcoff M, Lindqvist C & Kolm N. 2013. Sensory exploitation and plasticity in female mate choice in the swordtail characin. Animal Behaviour, 85, 891-898.

40. Kotrschal A, Rogell B, Bundsen A, Svensson B, Zajitschek S, Brännström I, Immler S, Maklakov AA & Kolm N. 2013. Artificial selction on relative brain size in the guppy reveals costs and benefits of evolving a larger brain. Current Biology, 23, 1-4.



39. John L. Fitzpatrick, Maria Almbro, Alejandro Gonzalez-Voyer, Niclas Kolm & Leigh W. Simmons. 2012. Male contest competition and the coevolution of weaponry and testes in pinnipeds. Evolution 66 (11): 3595-3604. doi:10.1111/j.1558-5646.2012.01713.x

38. Alexander Kotrschal, Björn Rogell, Alexei A. Maklakov & Niclas Kolm. 2012. Sex-specific plasticity in brain morphology depends on social environment of the guppy, Poecilia reticulata. Behavioral Ecology and Sociobiology 66: 1485-1492. DOI 10.1007/s00265-012-1403-7.

37. Kotrschal, A., Sundström, F. Devlin, R., & Kolm, N. 2012. Inside the heads of David and Goliath: environmental effects on brain morphology among wild and growth-enhanced salmon. Journal of Fish Biology, 81: 987-1002.

36. Kolm, N., Amcoff, M., Mann, R. & Arnqvist, G. 2012. Diversification of a food-mimicking male ornament via sensory drive. Current Biology, 22: 1-4

35. Fitzpatrick, J.L., Almbro, M., Gonzalez-Voyer, A., Hamada, S., Pennington, C., Scanlan, J. & Kolm, N. 2012. Sexual selection uncouples the evolution of brain and body size in pinnipeds. Journal of Evolutionary Biology 25, 1321-1330. Doi: 10.1111/j.1420-9101.2012.02520.x

34. Kotrschal A, Räsänen K, Kristjànsson BK, Senn M, Kolm N. 2012. Extreme Sexual Brain Size Dimorphism in Sticklebacks: A Consequence of the Cognitive Challenges of Sex and Parenting? PLoS ONE 7(1): e30055. doi:10.1371/journal.pone.0030055

33. Masahito Tsuboi, Alejandro Gonzalez-Voyer, Jacob Höglund and Niclas Kolm. 2012. Ecology and mating competition influence sexual dimorphism in Tanganyikan cichlids. Evolutionary Ecology: Volume 26, Issue 1, pp. 171-185. DOI: 10.1007/s10682-011-9489-3



32. Alejandro Gonzalez-Voyer & Niclas Kolm. 2011. Rates of phenotypic evolution of ecological characters and sexual traits during the Tanganyikan cichlid adaptive radiation. Journal of Evolutionary Biology: 24, 2378-2388.
DOI: 10.1111/j.1420-9101.2011.02365.x

31. Niclas Kolm & Göran Arnqvist. 2011. Environmental correlates of diet in the swordtail characin (Corynopoma riisei, gill). Environmental Biology of Fishes 92: 159-166. DOI 10.1007/s10641-011-9825-z

30. Alexei A. Maklakov, Simone Immler, Alejandro Gonzalez-Voyer, Johanna Rönn and Niclas Kolm. 2011. Brains and the city: big brained passerine birds succeed in urban environments. Biology Letters 7: 730-732. doi:10.1098/rsbl.2011.0341



29. Gonzalez-Voyer A & Kolm N (2010). Sex, Ecology and the Brain: Evolutionary Correlates of Brain Structure Volumes in Tanganyikan Cichlids. PLoS ONE 5(12): e14355. doi:10.1371/journal.pone.0014355

28. Göran Arnqvist and Niclas Kolm. 2010. Population differentiation in the swordtail characin (Corynopoma riisei ): a role for sensory drive? Journal of Evolutionary Biology 23, 1907-1918. DOI: 10.1111/j.1420-9101.2010.02055.x



27. Niclas Kolm, Alejandro Gonzalez-Voyer, Daniel Brelin and Svante Winberg. 2009. Evidence for small scale variation in the vertebrate brain: mating strategy and sex affect brain size and structure in wild brown trout (Salmo trutta). Journal of Evolutionary Biology 22, 2524-2531.

26. Mirjam Amcoff, Göran Arnqvist and Niclas Kolm. 2009. Courtship signalling with a labile bilateral signal: males show their best side. Behavioral Ecology and Sociobiology 63, 1717-1725.

25. Alejandro Gonzalez-Voyer, Svante Winberg, Niclas Kolm. 2009. Brain structure evolution in a basal vertebrate clade: evidence from phylogenetic comparative analysis of cichlid fishes. BMC Evolutionary Biology 9, 238.

24. Gonzalez-Voyer, A., Winberg, S. and Kolm, N. 2009. Distinct evolutionary patterns of brain and body size during adaptive radiation. Evolution 63, 2266-2274.

23. John L. Fitzpatrick, Robert Montgomerie, Julie K. Desjardins, Kelly A. Stiver, Niclas Kolm, and Sigal Balshine. 2009. Female promiscuity promotes the evolution of faster sperm in cichlid fishes. Proceedings of the National Academy of Sciences 106, 1128-1132. doi:10.1073/pnas.0809990106

22. Alejandro Gonzalez-Voyer, Svante Winberg and Niclas Kolm. 2009. Social fishes and single mothers: brain evolution in African cichlids. Proceedings of the Royal Society series B 276, 161-167. doi:10.1098/rspb.2008.0979



21. Alejandro Gonzalez-Voyer, John L. Fitzpatrick and Niclas Kolm. 2008. Sexual selection determines parental care patterns in cichlid fishes. Evolution 62-8, 2015-2016.



20. Emerson, B.C., & Kolm, N. 2007. Response to comments on Species Diversity can drive speciation. Ecography 30, 334-338.

19. Emerson, B.C., & Kolm, N. 2007. Species diversity can drive speciation: Reply. Ecology 88, 2135-2138.

18. Ridley, J., Kolm, N., Freckleton, R. P. & Gage, M. J. 2007. An unexpected influence of widely used significance thresholds on the distribution of reported P-values. Journal of Evolutionary Biology 20, 1082-1089.

17. Kolm, N., Stein, W. S., Mooers, A. Verspoor, J. J. & Cunningham, E. J. A. 2007. Can sexual selection drive female life histories?: A comparative study on Galliform birds. Journal of Evolutionary Biology 20, 627-638.



16. Kolm, N., Goodwin, N. B., Balshine, S. & Reynolds, J. D. 2006. Life history evolution in cichlids 2: Directional evolution of the trade-off between egg number and egg size. Journal of Evolutionary Biology 19, 76-84.

15. Kolm, N., Goodwin, N. B., Balshine, S. & Reynolds, J. D. 2006. Life history evolution in cichlids 1: Revisiting the evolution of life histories in relation to parental care. Journal of Evolutionary Biology 19, 66-75.



14. Emerson, B. C. & Kolm, N. 2005. Is speciation driven by species diversity? Reply. Nature 438, E2.

13. Kolm N, Ahnesjö I. 2005. Do egg size and parental care coevolve in fishes? Journal of Fish Biology 66, 1-17.

12. Emerson, B. C. & Kolm, N. 2005. Species diversity can drive speciation. Nature 434, 1015-1017.

11. Kolm, N. 2005. Differential allocation in the Banggai cardinalfish, Pterapogon kauderni: a reply to Vagelli & Volpedo. Environmental Biology of Fishes 72, 223-225.

10. N. Kolm, E.A. Hoffman, J. Olsson, A. Berglund, and A.G. Jones. 2005. Group stability and homing behavior but no kin group structures in a coral reef fish. Behavioral Ecology 16, 521–527.

9. Hoffman, E.A., Kolm N., Berglund, A., Arguello J.R. and Jones, A.G. 2005. Genetic structure in the coral-reef associated Banggai cardinalfish, Pterapogon kauderni. Molecular Ecology 14, 1367-1375.



8. Kolm, N. and Berglund, A. 2004. Sex-specific territorial behaviour in the Banggai cardinalfish (Pterapogon kauderni). Environmental Biology of Fishes 70, 375-379.

7. Hoffman, E.A., Arguello J.R., Kolm N., Berglund, A. and Jones, A.G. 2004. Eleven polymorphic microsatellite loci in a coral reef fish, Pterapogon kauderni. Molecular Ecology Notes 4, 342-344.

6. Kolm, N. 2004. Female courtship in the Banggai cardinalfish: honest signals of egg maturity and reproductive output? Behavioral Ecology and Sociobiology 56, 59-64.



5. Kolm, N. & Olsson, J. 2003. Rapid matching of egg size to mate attractiveness in the Banggai cardinalfish. Journal of Fish Biology 63, 144-151.

4. Kolm, N. and Berglund, A. 2003. Wild populations of a reef fish suffer from the “nondestructive” aquarium trade fishery. Conservation Biology 17, 910-914.



3. Kolm, N. 2002. Male size determines reproductive output in a paternal mouth-brooding fish. Animal Behaviour 63, 727-733.



2. Höglund, E., Kolm, N. and Winberg S. 2001. Stress-induced changes in brain serotonergic activity, plasma cortisol and aggressive behavior in Arctic charr (Salvelinus alpinus) is counteracted by L-DOPA. Physiology and Behavior 74, 381-389.

1. Kolm, N. 2001. Females produce larger eggs for large males in a paternal mouthbrooding fish. Proceedings of the Royal Society series B 268, 2229-2234.


1. Kolm, Niclas. 2003. Influence of Mate Quality on Reproductive Decisions in a Fish with Paternal Care.

Introduktionsuppsats/Introductory research essay

1. Niclas Kolm. 2001. Intersexual communication in fish. ISRN: UU-ZEK-IRE--75--SE.