In many species individuals may adopt one of several different reproductive behaviours, especially in the male sex. For instance, some males may invest in primary access to females through the defence of resources, whereas others circumvent this investment by either parasitising the investment of other males or by forced fertilizations. The different tactics can be largely genetically determined and maintained at equilibrium through frequency dependent selection, or depend on the phenotypic condition of the male. In the latter case, the fitness of the two tactics may differ, with less fit individuals adopting the “best of a bad job”.
Lamprologus callipterus nest male in spawning position on top of a Neothauma tanganicense shell in which a female is spawning, together with a parasitic dwarf male (see sketch).
We study evolutionary mechanisms involved in the origin and maintenance of alternative reproductive tactics in the shell brooding Lake Tanganyika cichlid Lamprologus callipterus. Three different male morphs occur in this species: (1) large nest building males; and two types of parasitic males: (2) medium sized opportunistic sneakers, and (3) dwarf males that are only 2% of the mass of nest males. Nest males collect empty snail shells in which females spawn and tend eggs, whereas opportunistic sneakers release sperm into the shell opening during spawning. Dwarf males have a different genotype and remain small for life. They rely on the availability of females just spawning with nest males, where they attempt to enter the shell past the spawning female to fertilize eggs from inside the shell. The Mendelian polymorphism of bourgeois and parasitic male tactics is stabilized by negative frequency dependent selection.
Alternative tactics are not confined to reproduction. On the contrary, consistent behavioural phenotypes diverging from each other are widespread across species and populations, and they appear in a wide range of functional contexts. In the cooperatively breeding cichlid Neolamprologus pulcher, for example, we find that alternative behavioural types are consistent throughout life and heritable, with social and other environmental effects triggering context-dependent behavioural decisions. We regard this behavioural consistency as a result of social niche specialisation.
Principal investigator: Michael Taborsky
Taborsky, M., Schütz, D., Goffinet, O. & van Doorn, G.S (2018) Alternative male morphs solve sperm performance/longevity trade-off in opposite directions. Sci. Adv. 4(5) eaap8563 [PDF]
Engqvist, L. and Taborsky, M. (2016): The evolution of genetic and conditional alternative reproductive tactics. Proc. R. Soc. B. 283:20152945 [PDF]
Wirtz Ocana, S., Meidl, P., Bonfils, D. & Taborsky, M. (2014): Y-linked Mendelian inheritance of giant and dwarf male morphs in shell-brooding cichlids. Proc. Roy. Soc. B 281: 20140253 [PDF]
Bergmüller R. & Taborsky M. (2010): Animal personality due to social niche specialisation. Trends Ecol. Evol. 25:504-511 [PDF]
Schütz D., Pachler G., Ripmeester E., Goffinet O. & Taborsky M. (2010): Reproductive investment of giants and dwarfs: specialized tactics in a cichlid fish with alternative male morphs. Funct. Ecol. 24:131-140 [PDF]
Oliveira R., Taborsky M. & Brockmann H.J. (2008): "Alternative Reproductive Tactics: An Integrative Approach". Cambridge University Press. 507pp. [PDF]