Reproductive ecology of impoverished pinweed (Lechea intermedia var. depauperata), a fire-associated narrow endemic from the boreal forest

Abstract

Impoverished pinweed (Lechea intermedia var. depauperata Hodgdon, Cistaceae) is a narrow endemic restricted to the dry, fire-prone Athabasca Plain in northeastern Alberta and northwestern Saskatchewan, Canada. Little is known about the ecology or life history of the taxon that could be used to inform conservation or management decisions. We investigated the reproductive biology of impoverished pinweed to determine whether it exhibits the suite of traits characterizing the temporal disperser syndrome, which is prevalent among Cistaceae species inhabiting fire-prone environments. Specifically, we examined the soil seedbank, characterized seed production, and conducted three sets of germination trials examining the interaction of heat and scarification, burial, and alternate wetting and drying. Our results show that impoverished pinweed is similar to other Cistaceae with respect to seed production, dispersal, and germination, supporting the classification of impoverished pinweed as a temporal disperser. Exposing seeds to temperatures between 125 and 175 °C significantly increased germination as compared with the untreated controls. We discovered an additional cause of seed loss incidentally; here we report the first western Canadian records of Anthonomus pusillus Le Conte, a seed-predating weevil. Our results suggest that the temporal and spatial dynamics of impoverished pinweed populations are strongly shaped by fire and the distribution of soil seedbanks.