[Resumen extraído de la fuente original]

It is admitted that the origin of the height of the radical vowel of Galician and Portuguese sigo ~ siga ‘I follow / I go on’ and cubro ~ cubra ‘I cover’ is problematic: the expected vowel in that context, through a regular phonological evolution, should be mid high, not high. Given the irregular origin of the high vowel in Galician, Portuguese and Spanish, that the three languages share the unexpected height and that it seems that the high vowel first appeared and was consolidated in the central dialects of the Peninsula, I will propose that forms like sigo and cubro were originated in those central dialects and were taken and spread into the occidental dialects by a language contact situation. As the contact was more prolonged and intense in Galicia than in Portugal, Galician promoted variants like pido ~ pides ~ pide ~ pida (‘I ask for’), shared with Spanish, and diverged in this respect from Portuguese, which blocked their spreading.