Gigaspora gigantea: seasonal abundance and ageing of spores in a sand dune

Abstract

Seasonal abundance of spores of the arbuscular mycorrhizal (AM) fungus Gigaspora gigantea in four different stages of vigour was monitored in a coastal sand dune in Rhode Island. Stages included healthy, moribund, dead and invaded spores. Invaded spores contained spores of other AM fungi. The sand dune was sampled monthly from March 1989 to February 1990. Healthy spores were most abundant in winter and least abundant in summer. An opposite trend was found for dead spores. Moribund spores were most numerous in spring and least abundant in autumn. Abundance of healthy, moribund and dead spores showed significant seasonal variation, but no significant seasonal trend was evident for the numbers of invaded spores. The relative abundance of healthy spores was negatively correlated with that of dead spores. Newly formed spores persisted for about five months before becoming moribund. Individual moribund spores died over a three-month period. The total number of spores of G. gigantea , regardless of condition, was more or less constant throughout the year.