How are basidiospore size measurements affected by drying?

Abstract

Spore size plays a crucial role in the demarcation of fungal species. Spore size is measured from either fresh or, more frequently, dried fungal specimens. In the present study, we investigate the impact of drying on the basidiospore size of three ectomycorrhizal species, and the bias it can generate on the taxonomic identification of fungal species. We measured a total of 1109 basidiospores of Amanita masasiensis, 2322 basidiospores of Lactifluus gymnocarpoides, and 920 basidiospores of Russula congoana from fresh sporocarps and spore prints. After specimens and spore prints were dehydrated for 24h at 50°C, we measured 1200 basidiospores of A. masasiensis, 2348 basidiospores of L. gymnocarpoides and 1150 basidiospores of R. congoana. The effects of drying on length, width, and length/width quotient (Q) values were tested using a linear mixed model to control for inter-individual variation. Drying reduced the basidiospore length and width of A. masasiensis by 10% and 16% respectively, resulting in a 7% increase in the quotient Q, while both the length and width of basidiospores of L. gymnocarpoides and R. congoana were reduced by 3% and 6% respectively, with no change in Q. This study suggests that greater attention should be given to the condition of the spores when spore size is used as a taxonomically discriminative characteristic. This is especially relevant for the taxonomy of cryptic species, where other discriminative characteristics may be lacking.