Comparative Reproductive Biology of Two Alpine Primrose Species

Abstract

Primula angustifolia and Primula parryi are common alpine primroses in Colorado. We examined the reproductive biology of these species to determine (1) if they were fully distylous (2) what differences in pollinators and in reproductive allocation and success might exist between the species, and (3) whether reproduction was limited by pollen availability during the period of study. We found both taxa to be fully distylous. Primula parryi has numerous, diverse pollinators, a high seed/ovule ratio, and high fecundity. Primula angustifolia has fewer, less diverse pollinators, lower seed/ovule ratios, and lower fecundity. The greater reproductive success of P. parryi may reflect its inflorescence structure and supply of attractants and rewards. Reproduction in both species appears to be limited to some extent by pollen availability, although more so in P. parryi than in P. angustifolia. These results demonstrate while distyly, with obligate outcrossing and reliance on insect pollen vectors, can be a viable reproductive strategy even in a severe environment, it functions differently even in closely related species and understanding individual pollination systems should be a focus for research on other distylous species.