Increasing taxonomic resolution in pollen identification: Sample size, spatial sampling bias and implications for palaeoecology

► Small sample sizes must be avoided when determining pollen identification criteria. ► Sample size should approach or exceed pollen from 30 individuals per species. ► Sampling efforts should focus on using more plants, instead of more pollen per plant. ► Regional differences in morphology introduce bias into pollen identification methods. ► Identification criteria should be based on pollen from across species ranges.