Selection against hybrids between the two populations may cause reinforcement, which is the evolution of traits that promote mating within a species, as well as character displacement, which is when two species become more distinct in appearance.
The results indicate that, even though the ductile reinforcements may alter the evolution and morphology of the shear bands, the overall failure behavior is still controlled by the metallic glass matrix, leading to very little or no improvement in the composite ductility in comparison to the ductility of metallic glass matrix.
Studies in Drosophila have shown that the genetic architectures of mating discrimination could differ significantly with or without reinforcement [5], suggesting that the evolution of assortative mating may be more complicated than expected.
Natural selection against hybridization (i.e. reinforcement) can lead to the evolution of a genital "lock and key" mechanism and complex genitalia [38].
Where gene flow between somewhat distinct genomes is not contained by the formation of hybrid zones [ 8] or abrupt speciation [ 16], it can have numerous outcomes; reinforcement of reproductive barriers, the evolution of a new species, the loss of one or both parental species, limited adaption due to homogenization, or provide a means to pass adaptive traits between populations [ 6- 8, 17, 18].
We describe the evolution of reinforcement activities within eighteen months (June 2008-December 2009) of PAR focussed on institutionalization of clinical audits and addressing gaps in knowledge and skills.
Pseudotetraploidy and long generation times (i.e. slow evolutionary rates) might also buffer against possible effects of intrinsic genomic incompatibilities and slow down the evolution of reinforcement mechanisms, which would allow introgression between genera separated by more than 20 ma of evolution [ 18– 20].
At constant silica volume fraction, this indicates depercolation of the filler, thereby providing a microscopic explanation of the evolution of rheological reinforcement.
We first present the evolution of the reinforcement activities during the PAR before presenting our understanding of the barriers to and facilitators of the implementation process that shaped this evolution.
This also supports the general view that reinforcement plays an important role in the evolution of reproductive isolation [ 40, 41].
