Releasing pheasant is a very common practice mainly for hunting. Game farms use often pheasants of different strains (e.g. mongolicus and torquatus). Is it possible that crossing different subspecies (in farm or as consequenc of the releasing of mixed stock) causes a decrease of the fitness of released population?
Yes, it could if hybrids are not well suited to the environment (ie: coloration, resource requirements etc), or if the hybrids are not a desirable mate choice for other ssp or among other hybrid individuals.
As I remember from my university course of genetics, hybridization of distant genotypes often decrease fitness of progeny, when hybridization of genotypes with average genetic distance gives the best result.
In Bulgaria along the Bulgarian Danube River there are pheasants with mixed marks between mongolicus and karpowi, which are successfully breeding. In these areas of Bulgaria there was no natural pheasant population in the past, but now there is a breeding of some of the crossed subspecies from farms. If the fitness of the released population was bad, then should these birds not survive in the future or not multiply? At the same time, in the southern Bulgaria, in the natural habitats of colchicus, turquatus was release, resulting in the disappearance of colchicus as a subspecies of the respective habitats. Probably there are additional conditions determining the fitness of released population.
The only aspect of biometry differences between these supspecies could not explain partly a variation of this fitness ? As I remember in its introduction countries lightweight pheasants seem to be favoured in the survival.
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