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Evolution of reproductive barriers and its implications for adaptive speciation

Final Report Summary - ADAPTIVE SPECIATION (Evolution of reproductive barriers and its implications for adaptive speciation)

Non-allopatric speciation is defined as speciation without physical separation of lineages, implying that individuals of one population are within the 'normal cruising range' of individuals of the other population. Non-allopatric speciation was considered rare in nature, because models suggested that it was possible only under restrictive conditions and there were few well-supported examples. However, recent theoretical and empirical work has altered this view and it now seems that this mode of speciation may provide an important contribution to biological diversity. My aim was to contribute to this field using the marine gastropod littorina saxatilis as a model.

The project objectives were to test the contributions of genetic differentiation and phenotypic plasticity to both adaptation and reproductive isolation between the E and S morphs of l. saxatilis using three approaches:
1. analyse transects on two separate small islands, using numerous amplified fragment length polymorphism (AFLP) markers and morphometric analysis in order to obtain estimates of gene flow and selection,
2. determine the contribution of plasticity to local adaptation and assortative mating using snails reared under experimental conditions, and
3. test for the possibility of enhanced assortative mating, i.e. reinforcement, in the centre of the hybrid zone between morphs.