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The genus Lithospermum
The genus Lithospermum is comprised of herbaceous perennials in the forget-me-not familiy (Boraginaceae). There are about 60 species worldwide and 13 species in North America . Species within the genus exhibit mating systems that range from fully selfing to fully outcrossing. Two spring-flowering species brighten sandy, open habitats in southern Manitoba, Lithospermum incisum (fringed puccoon) and L. canescens (hoary puccoon).
Evolution of Mating Systems
Most flowers produce both male and female organs. This situation introduces the possibility of extreme inbreeding due to self-fertilization. Indeed, some species dispense with pollination vectors altogether and self-pollinate automatically. Other species evolve elaborate adaptations to avoid self-pollination. An example is heterostyly, in which 2 mating types have reciprocally positioned sex organs. A third possibility is to have the best of both worlds: out-breed when pollen vectors are available and self-pollinate when they are not. This may be advantageous when pollinators are unreliable or the plants range exceeds that of its’ pollinators.
All three of the above mating systems occur in the genus Lithospermum. We are studying the two species that occur in Manitoba . Hoary puccoon (L. canescens) is heterostylous and out-breeding, whereas fringed puccon (L. incisum) produces both large, out-breeding (“chasmogamous,” i.e. open) flowers and tiny, self-pollinating (“cleistogamous,” i.e., closed) flowers. The two species often occur in the same sites, and provide an opportunity for studying contrasting mating systems in species that are otherwise similar. We are conducting genetic analyses of each species to estimate genetic variation and quantify their mating systems. We are also studying the pollination biology of L. incisum, and conducing an experiment to measure the possibility that inbred seeds from closed flowers have lower fitness than out-bred seeds from open flowers.