Dr. Kalina Kapralova, Faculty of Life and Environmental Sciences, University of Iceland will present her research:
How is phenotypic integrity of sympatric morphs maintained in the face of potential gene flow? The Arctic charr (Salvelinus alpinus) of Thingvallavatn is ideally suited to address this question: i) it has young evolutionary history, ii) it has diverged into four morphs with distinct variation in life history characteristics, behavior and trophic morphology, suggesting rapid adaptive diversification, possibly followed by or causing build-up of reproductive barriers. Here we focus on the two smaller Thingvallavatn morphs, planktivorous- (PL) and small benthic-charr (SB), which have diverged along the limnetic - benthic ecological axis. While their spawning overlaps spatially and temporally, seemingly presenting ample opportunities for cross-mating, they constitute distinct populations, which suggests effective reproductive barrier(s).
The central hypothesis underlying our investigation is that reproductive isolation between SB and PL charr is partly due to strong negative selection against hybrid offspring and/or differences in the precise spawning location, exact timing of spawning, and/or mating behavior. Our preliminary results suggest hybrid crosses between PL and SB might have a lower fitness compared to the pure parental breeds. Namely our results show that upon hatching F1 reciprocal hybrids between SB and PL have significantly smaller head sizes and grow slower than offspring from pure crosses. Moreover, significant (transgressive) differences in craniofacial morphology were detected between the hybrid crosses and the pure parental crosses. SB and PL appear to utilize the same general area for spawning. However, PL and SB spawning differ slightly temporarily (PL emerge later in the evening than SB) and spatially (PL is observed in greater depth).