Special Interest Group Meeting

Cryptic speciation: how common is it and how should it be handled taxonomically?

David L Hawksworth, Departamento de Biologia Vegetal II, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza Ramon y Cajal, Madrid 28040, Spain

The different uses of the term "cryptic" in systematics are considered, and a pragmatic working definition is proposed: "Populations which are phylogenetically distinct and able to reproduce themselves, by sexual means or otherwise, but which are distinguished by molecular or other features that are either not evident macroscopically or generally overlooked. The approaches and options used for the recognition and naming of cryptic species in different groups of organisms are assessed, with examples drawn from non-lichenized fungi, insects, and plants. Cryptic speciation is proving to be widespread in both lichenized and non-lichenized fungi, and is perhaps the most important place in which the huge number of "undescribed fungi" forecast to be present on Earth are hidden. Almost all cases in which groups of plant pathogenic fungi have been investigated in detail by modern methods reveal the occurrence of hitherto unrecognized cryptic species. As the identification of cryptic species may not be practical outside a modern molecular laboratory, an acceptable way of referring to such groups of species is required. "Complex" is commended here for use where the populations are closely related, i.e. have a recent shared common ancestor. In some situations, however, the option of recognizing subspecies could be more appropriate. In contrast, in cases where the cryptic taxa are not closely related but a result of convergence, i.e. they do not either occupy the same clade or have a recent common ancestor, it has to be recognized that the "complex" approach could give a misleading impression of affinity. Non-taxonomists, especially ecologists, biogeographers and conservationists, need to be aware that not all cryptic species represent identical phylogenetic situations, and that "complexes" can include taxa with different ecological requirements. The recognition and characterization of cryptic species is a burgeoning and exciting activity in current systematics,and a major challenge for mycologists of all kinds, not least lichenologists.