Morphotypes, varieties, or subspecies?: Genetic diversity and differentiation of four Saintpaulia (Gesneriaceae) morphotypes from the East Usambara Mountains, Tanzania

Abstract

Saintpaulia (H. Wendl.) is a forest-dependent, endangered plant genus endemic to Tanzania and Kenya. The taxonomy of Saintpaulia from the Usambara Mountains and adjacent lowlands in north-eastern Tanzania is problematic because of the morphological similarity of the species and the presence of considerable intraspecific variation. Conventional molecular phylogenetic methods have failed to reveal the genetic structure of this Saintpaulia complex. In this study, we assessed the genetic composition of 12 Saintpaulia populations, representing four different morphotypes, from the East Usambara Mountains using inter-simple sequence repeat (ISSR) markers. Relatively high genetic diversities were observed within populations (mean h = 0.320), indicating their adaptive potential. Little genetic differentiation amongst populations (mean F st = 0.063) and the genetic divergence of the rosulate and trailing morphotypes support the hypothesis of ongoing divergent evolution within the East Usambara metapopulation(s) of Saintpaulia. © 2008 The Linnean Society of London.