Assessing the impacts of gene flow between endemic Hawaiian cotton, Gossypium tomentosum, and two commercial cotton species

Abstract

To determine the ease with which Hawaiian cotton, Gossypium tomentosum, hybridizes with two introduced commercial cotton species, G. hirsutum and G. barbadense, reciprocal crosses were carried out in a controlled setting. To assess the impacts of gene flow on fitness and fecundity, F1 hybrids were grown in a common garden plot along with parental species. Results show that there are no strong hybridization barriers between Gossypium tomentosum and either commercial cotton species. In hand pollination trials, G. tomentosum is more prone to accept foreign pollen than either commercial species, with higher rates of hybridization. The same hand pollination trial showed that G. tomentosum hybridizes more freely with G. hirsutum than with G. barbadense. All F1 hybrids show significantly greater fitness and fecundity than conspecific F1 G. tomentosum suggesting that natural F1 hybrids could outcompete native cotton populations for habitat and resources should they become established.