Dispersal and monoecy in Atriplex cinerea (Chenopodiaceae)

Abstract

Atriplex cinerea Poir., indigenous to southern coasts of Australia, has occasionally been found along the shores of Cook Strait, New Zealand. Buoyancy tests have shown that most fruits stay afloat less than 5 weeks. Published data from drift bottle and drift card experiments indicate that it takes at least 300 days for a floating object to cross the Tasman Sea. It is therefore unlikely that A. cinerea fruits have arrived in New Zealand unaided. Transport on rafts of flotsam or by migrating birds are mooted possibilities. Atriplex cinerea is dioecious or monoecious. Monoecious plants are self-compatible and thus one individual could start a new population. Inspection of herbarium specimens and plants in the field showed that there is at least a one in five and possibly a better than a one in three chance that a plant is monoecious. Atriplex cinerea is hexaploid. Some plants of A. canescens (Pursh) Nutt., a polyploid species from North America, change their gender from year to year owing to the sexually labile nature of tetraploid and hexaploid genotypes. Inherent genetic factors as well as seasonal weather conditions have an influence on these changes. It would be interesting to find out whether this also happens in A. cinerea. As A. cinerea is used for saltland rehabilitation, a study of its variability could benefit the selection of better-adapted strains.