Winkler, Lennart

Tribolium Lab – Janicke & Winkler

WinklerI am PhD student, supervised by Tim Janicke and Klaus Reinhardt.
My project examines how sexual selection is aligned with natural selection. We aim to investigate the influence of sexual selection on the capacities for adaption of species to novel environments and its influence on population fitness. Theory predicts that by reducing the frequency of deleterious mutations / mutation load, sexual selection might increase overall population fitness, while for example sexual conflict might reduce it. In this project we will (amongst other techniques) apply meta-analyses and experimental evolution (using the model system Tribolium castaneum) to test these hypotheses.

Some current interests are: Sexual selection, sperm competition, selfish genetic elements, genic capture, plasticity


  • Carlitz, E. H. D. et al. Steroid hormones in hair reveal sexual maturity and competition in wild house mice (Mus musculus domesticus). Sci. Rep. 9, 1–10 (2019).
  • Winkler, L., Kirch, L. M., Reinhold, K. & Ramm, S. A. Impact of low sperm competition on male reproductive trait allometries in a bush-cricket. BMC Evol. Biol. 19, 185 (2019).
  • Winkler, L. & Ramm, S. A. Experimental evidence for reduced male allocation under selfing in a simultaneously hermaphroditic animal. Biol. Lett. 14, (2018).

Building BIO Room 257



Twitter: @lennarthamburg

Current students:

Birte Martens (BSc Student): Thesis on ‘Costs and benefits of male same-sex (‘homosexual’) copulations

BSc and MSc projects in the Tribolium lab

We are happy to host projects and/or theses in one of the outlined or self-developed projects. If you are interested in joining our team, please get in contact.

Evolutionary and behavioural biology

Supervisor: Dr. Tim Janicke, Lennart Winkler (Seminargebäude, SE 24a)

Study organism: red flour beetle Tribolium castaneum

Project start: any time

1. Sex-specific genetic variance/heritability in reproductive success

The genetic architecture of male and female fitness components predict evolutionary change. Genetic correlations between male and female fitness inform us about whether male and female traits can evolve independently or whether high-fitness females produce high-fitness males and vice versa. This project will repeat a previous estimation of genetic variances (Holman and Jacomb 2017) that failed to consider male-male competition. It includes quantitative genetics and a breeding design (full-sib/half-sib).

2. Strategic sperm allocation in the red flour beetle

Not only females but also males are expected to allocate their gametes prudently. Sexual selection theory predicts that males should adjust the number of transferred sperm in response to the risk of sperm competition. In T. castaneum males transfer a spermatophore to the female, containing sperm and seminal fluid (Qazi et al. 2015). It has been shown that the spermatophore is apparently only filled with sperm by the male, after the spermatophore is already transferred to the female (Fedina 2007). This might enable males to plastically adjust the amount of transferred sperm during mating. We might test the hypothesis of plastic sperm allocation in response to sperm competition by comparing the number of transferred sperm between virgin and mated females or between females of different size. This project requires preliminary experiments to establish a protocol to quantify the amount of sperm transferred to a female. The project would involve observation of mating behaviour and sperm microscopy techniques.

3. Morphology of male reproductive organs

The morphology of the male penis has potentially substantial influence on the reproductive success of males. This implies that sexual selection influences the evolution of male genital morphology. The male genital morphology of Tribolium castaneum might play an important role in male fertilization success, by influencing the outcome sperm competition and post-copulatory female choice (Haubruge et al. 1999; Arnaud et al. 2001). We would like to quantify male genital morphology (length measures and geometric morphometrics) to investigate if these measures influence male paternity success. Furthermore, one could study the allometry of the male penis to infer selective pressures. This project requires preliminary experiments to establish a protocol to dissect and measure the male copulatory organ. The project would include microscopy techniques and potentially behavioural observations.

4. Impact of population density on sexual selection in the red flour beetle

Sexual selection is considered a potent evolutionary force explaining the bewildering diversity of differences between males and females. Recent work suggests that the strength of sexual selection can vary substantially among populations but we are only beginning to understand this inter-specific variation (but see McLain 1982, Conner 1989 & Levitan 2004). One of the most prominent demographic factors showing often drastic inter-specific differences is density. However, we know surprisingly little about the effect of density on the strength and form of sexual selection. In this project we will quantify so-called Bateman metrics (Bateman 1948) to explore the causal relationship between density and sexual selection using the red flour beetle as a model system. Main tasks of this project include animal breeding, behavioural observations/recordings and statistical modelling. 


Arnaud L, Haubruge E, Gage MJG. 2001. Morphology of Tribolium castaneum male genitalia and its possible role in sperm competition and cryptic female choice. Belg J Zool.(131 (2)):111–115.

Bateman A. J. 1948. Intra-Sexual Selection in Drosophila. Heredity (Edinb). 2:349–368. 

Conner J. 1989. Density-dependent sexual selection in the fungus beetle, Bolitotherus cornutus. Evolution (N Y). 43(7):1378–1386.

Fedina TY. 2007. Cryptic female choice during spermatophore transfer in Tribolium castaneum (Coleoptera: Tenebrionidae). J Insect Physiol. 53(1):93–98.

Fedina TY, Lewis SM. 2008. An integrative view of sexual selection in Tribolium flour beetles. Biol Rev. 83:151–171.

Holman L, Jacomb F. 2017. The effects of stress and sex on selection, genetic covariance, and the evolutionary response. J Evol Biol. 30(10):1898–1909.

Levitan DR. 2004. Density-dependent sexual selection in external fertilizers: Variances in male and female fertilization success along the continuum from sperm limitation to sexual conflict in the sea urchin Strongylocentrotus franciscanus. Am Nat. 164(3):298–309.

Lewis SM, Tigreros N, Fedina T, Ming QL. 2012. Genetic and nutritional effects on male traits and reproductive performance in Tribolium flour beetles. J Evol Biol. 25(3):438–451.

McLain DK. 1982. Density dependent sexual selection and positive phenotypic assortative mating in natural populations of the soldier beetle, Chauliognathus pennsylvanicus. Evolution (N Y). 36(6):1227–1235.

Qazi MCB, Herbeck JT, Lewis SM. 2015. Mechanisms of Sperm Transfer and Storage in the Red Flour Beetle ( Coleoptera : Tenebrionidae ). Ann Entomol Soc Am. 89(6):892–897.