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Re: Species concepts

>Has anyone introduced a system similar to the following?

>Fertile offspring = same species
>Infertile offspring = different species of same genus
>No offspring = different genera

>I don't know how much it would alter existing classifications, but having
>some objective definition of genera would be good.

It would give weird results:

Fertile offspring = same species => All large falcons are a single species

Infertile offspring = different species of same genus => Mergus and Bucephala are the same genus and so is Anser and Branta

No offspring = different genera => Sturnus vulgaris and Sturnus unicolor are in different genera.

The problem is that the capability to interbreed seems to be dependent on the degree of differences in the genes regulating the embryonal development, which is not necessarily well correlated with
the degree of morphological difference. Also complete reproductive isolation can result from changes of just a few genes if these affect reproductive behaviour or timing. I still think that the BSC, i. e. reproductive isolation *in the wild* is the best species concept, after all it is the one used by the critters themselves, but of course they haven't studied cladistics.

Tommy Tyrberg