Cytogenetics of Hibiscadelphus (Malvaceae): A Meiotic Analysis of Hybrids in Hawaii Volcanoes National Park

Abstract

The chromosome number of 2n = 20 11 reported here is the first determination for Hibiscadelphus giffardianus Rock and H. distans Bishop & Herbst. An earlier report of the same number for H. hualalaiensis Rock is substantiated. Cytogenetic analysis of H. x puakuahiwi Baker & Allen, a hybrid cross between H. giffardianus and H. hualalaiensis suggests that chromosome pairing and microsporogenesis are not affected in the first generation. However, although chromosome pairing is normal at diakinesis in the seven F2S analysed, subsequent stages of meiosis and microsporogenesis are severely disturbed and result in the formation of a high percentage of abnormal meiospores in some of the plants. Nevertheless, the apparent lack of hybrid breakdown in two of the F2 plants and the presence of probable F3S in one area suggest that gene flow between the two taxa is possible, and, therefore, must be taken into consideration if these two endangered species are to be maintained as distinct entities.