Two distinct populations of P. domesticus and hispaniolensis exist in eastern Portugal, with some hybridization. According to R. F. Johnston (pers. comm.) the frequency of hybridization could be considerable, 20 % as he estimated in a small sample of Ladoeiro. These hybrids were not easily detected. But no matter however the frequency of actual hybrirdization may be in nature, it seems it is not sufficient to produce a hybrid swarm. Until now good intermediate phenotyps are not seen in the area. There is no breakdown of reproductive isolation although a little introgression could take place.

No sharp separation between the two populations is found. The individuaIs of both species can live together, often breeding in the same support (Sacarrão 1973; Sacarrão and Soares 1975). In such conditions the reproductive isolation probably is assured mainly by ethological barriers.

In Spain the conditions seem to be in part different as is shown comparatively in the next table: