Roger K. Butlin

TL;DR: A maximum-likelihood approach to fitting a two-dimensional cline to geographical variation in quantitative traits and for estimating associations of population mean with local habitat is developed and reveals a cline in peg number approximately 30 km south of the Picos de Europa Mountains that shows substantial deviations in population mean compared with the expectations of simple tension zone models.

TL;DR: Morphological and molecular evidence shows that An.

TL;DR: The genetic basis of parallel divergence in the marine snail Littorina saxatilis, which has repeatedly evolved coexisting ecotypes adapted to either crab predation or wave action, is asked and a polygenic basis of divergent traits might allow for multiple distinct molecular mechanisms generating the same phenotypic patterns.

TL;DR: The data confirm the presence of two cryptic species, A and C, within An.

TL;DR: It is argued that a combination of heterosis and divergent selection can explain the observed patterns and should be considered in other systems spanning environmental gradients.