T clusiana indeed range from diploid to pentaploid. I don't know if they are in mixed populations. Only the pentaploid seems to have expanded as far as Spain due to the fact it makes stolons. I suppose the diploid ( T aucheriana) does not make stolons. It is for sure that T clusiana has not contributed anything ( despite some suggesting otherwise) to the gesneriana type cultivars of today. They cannot be crossed and differ strongly in nuclear DNA content