Host-specificity, host-exclusivity, and host-recurrence in saprobic fungi

Estimates of global fungal numbers rely heavily on the ratios of unique fungi to host plants. Evidence for host-specificity, which is basic to our understanding of host to fungus ratios, is therefore explored in this review. There is considerable evidence that some endophytes, pathogens and mycorrhizal fungi are host-specific. Host-specificity however, may be an unwise term for saprobic fungi, and 'host-exclusivity' and 'host-recurrence' may be more appropriate terms. Concepts of host-specificity, host-exclusivity and host-recurrence are therefore defined and discussed. Suggestions for future work needed in order to establish host-exclusivity and host-recurrence in saprobic fungi are made.