Final Report Summary - PLASTICITYSPECIATION (Phenotypic plasticity and speciation in cichlids) The aim of the project was to empirically test a set of expectations stemming from a body of theoretical work on the impact of phenotypic plasticity – i.e. the ability of a single genotype to produce different phenotypes in different environments – on diversification and speciation. According to this previous work, when in the presence of a trade-off, a phenomenon called “genetic assimilation” is expected. This is a process whereby an environmentally induced phenotype becomes canalized through selection acting upon the developmental system. The expected outcome when comparing the ancestral state to the state derived via genetic assimilation is a reduction in plasticity (i.e. the derived form has a smaller phenotypic change in response to an environmental stimulus).Midas cichlid fish are an ideal system to test such an hypothesis as derived species from a crater lake environment have diverged very rapidly from their ancestors from a tectonic lake environment. Due to this rapid divergence, both ancestral and derived forms are still present in Nicaraguan lakes and can be, then, subjected to experimental manipulation.In this project broods of the two species Amphilophus citrinellus (ancestral species from Lake Nicaragua) and A. zaliosus (derived species from Lake Apoyo) were produced from wild-caught, lab-reared fish currently hosted in the University of Konstanz animal facilities (TFA). They were raised and, then, subjected to the differential food treatment (hard diet/soft diet).From the digital photographs of the pharyngeal jaws of the treatment and control groups, Dr. Fruciano digitized a set of 12 points. After generalized Procrustes analysis, the allometric variation was removed by multivariate regression of shape variables on body centroid size. Based on this data now corrected for allometry, Dr. Fruciano tested for differences in pharyngeal jaw shape between treatment and control groups and visualized their differences in means.The main message is that the difference in means in A. zaliosus between treatment and control is lower than the one in A. citrinellus, suggesting lower levels of plasticity in the derived species.This agrees well with the theory and anticipated results as outlined in the original proposal. Related documents final1-marie-curie-327875-summary.pdf
