The Sunshine periwinkle plant blooms in June while Summer periwinkle, a close relative of Sunshine periwinkle , blooms in August. A researcher is raising a population of Summer periwinkle in a controlled growth chamber. Over time the researcher manipulated the day length in the growth chamber and eventually manages to induce some individuals of Summer periwinkle to bloom in June. The researcher finds that she can cross these individuals with Sunshine periwinkle individuals and they produce viable, fertile offspring. What can she conclude about Sunshine periwinkle and Summer periwinkle