Niclas Kolm

Niclas Kolm


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Works at Department of Zoology
Telephone 08-16 40 50
Visiting address Svante Arrheniusväg 18 B
Room D 513
Postal address Zoologiska institutionen: Etologi 106 91 Stockholm

About me

I am an evolutionary biologist with broad interests in life histories, sexual selection, speciation, and animal behavior. My main interest lie in brain evolution and the link between variation in brain morphology and behaviour. I study this in a variety of taxa (Cichlids, Pipefishes and Seahorses, Birds, Pinnipeds, Cetaceans, Salmonids, Poeciliids) using phylogenetic comparative analysis and laboratory experiments.


Currently, most of the work in my group builds on two systems:


We have a database with data on brain morphology, behaviour, life history, mating system, parasites, various aspects of ecology etc for ca 70 species of Lake Tanganyika cichlids and a recently collected similar database for pipefishes and seahorses. We use these databases to perform phylogenetic comparative analyses to test various hypotheses in a macroevolutionary framework.


We use our recently developed guppy selection lines with 14 % difference in brain size to perform experimental tests of several hypotheses concerning brain evolution and the link between brain morphology and physiology and behaviour. For this work, we have over 250 m2 of lab space with room for >4000 aquaria and six separate rooms for behavioural assays.

Postdoctoral Researchers
Alexander Kotrschal
Séverine Büchel
James Herbert-Read aka Teddy (Teddy's main supervisor is David Sumpter at the mathematics department Uppsala University)

Stephanie Fong
Alberto Corral Lopez
Wouter van der Bijl


A selection from Stockholm University publication database
  • 2017. M. Tsuboi (et al.). Journal of Evolutionary Biology 30 (1), 150-160

    Brain size varies greatly at all taxonomic levels. Feeding ecology, life history and sexual selection have been proposed as key components in generating contemporary diversity in brain size across vertebrates. Analyses of brain size evolution have, however, been limited to lineages where males predominantly compete for mating and females choose mates. Here, we present the first original data set of brain sizes in pipefishes and seahorses (Syngnathidae) a group in which intense female mating competition occurs in many species. After controlling for the effect of shared ancestry and overall body size, brain size was positively correlated with relative snout length. Moreover, we found that females, on average, had 4.3% heavier brains than males and that polyandrous species demonstrated more pronounced (11.7%) female-biased brain size dimorphism. Our results suggest that adaptations for feeding on mobile prey items and sexual selection in females are important factors in brain size evolution of pipefishes and seahorses. Most importantly, our study supports the idea that sexual selection plays a major role in brain size evolution, regardless of on which sex sexual selection acts stronger.

  • 2017. Alison E. Wright (et al.). Nature Communications 8

    Sex chromosomes evolve once recombination is halted between a homologous pair of chromosomes. The dominant model of sex chromosome evolution posits that recombination is suppressed between emerging X and Y chromosomes in order to resolve sexual conflict. Here we test this model using whole genome and transcriptome resequencing data in the guppy, a model for sexual selection with many Y-linked colour traits. We show that although the nascent Y chromosome encompasses nearly half of the linkage group, there has been no perceptible degradation of Y chromosome gene content or activity. Using replicate wild populations with differing levels of sexually antagonistic selection for colour, we also show that sexual selection leads to greater expansion of the non-recombining region and increased Y chromosome divergence. These results provide empirical support for longstanding models of sex chromosome catalysis, and suggest an important role for sexual selection and sexual conflict in genome evolution.

  • 2017. A. Hayward (et al.). Journal of Evolutionary Biology 30 (6), 1056-1067

    Parasite diversity and abundance (parasite load) vary greatly among host species. However, the influence of host traits on variation in parasitism remains poorly understood. Comparative studies of parasite load have largely examined measures of parasite species richness and are predominantly based on records obtained from published data. Consequently, little is known about the relationships between host traits and other aspects of parasite load, such as parasite abundance, prevalence and aggregation. Meanwhile, understanding of parasite species richness may be clouded by limitations associated with data collation from multiple independent sources. We conducted a field study of Lake Tanganyika cichlid fishes and their helminth parasites. Using a Bayesian phylogenetic comparative framework, we tested evolutionary associations between five key host traits (body size, gut length, diet breadth, habitat complexity and number of sympatric hosts) predicted to influence parasitism, together with multiple measures of parasite load. We find that the number of host species that a particular host may encounter due to its habitat preferences emerges as a factor of general importance for parasite diversity, abundance and prevalence, but not parasite aggregation. In contrast, body size and gut size are positively related to aspects of parasite load within, but not between species. The influence of host phylogeny varies considerably among measures of parasite load, with the greatest influence exerted on parasite diversity. These results reveal that both host morphology and biotic interactions are key determinants of host-parasite associations and that consideration of multiple aspects of parasite load is required to fully understand patterns in parasitism.

Show all publications by Niclas Kolm at Stockholm University

Last updated: September 19, 2017

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