Goodbye morphology? A paradigm shift in the delimitation of species in lichenized fungi

Abstract

Accurate species delimitations are crucial for ecological and conservation studies, assessments of biotic diversity, and identifying factors driving diversification. Estimates suggest that the vast majority of fungal species are currently unknown. Although many undescribed fungal taxa are expected to be indentified within understudied groups and from underexplored areas, mounting evidence suggests a substantial number of unrecognized fungal species are likely hidden within traditional phenotypebased species in lichen-forming fungi. Molecular genetics has revolutionized our ability to assess traditional species concepts and provides additional tools for robust species delimitation. In general, lichens display few taxonomically usefully characters; therefore molecular data have gained great importance in delimiting fungal species in lichen symbioses. As a result, the taxonomic value of phenotypical characters is now much better understood, and in many cases previously overlooked characters have been identified supporting molecular-based species circumscriptions. Although in some cases molecular research has verified traditional hypotheses, most studies repeatedly show that our current interpretation of morphological and chemical characters is inadequate to accurately characterize diversity. Here we report on the role of molecular data in understanding species-level diversity in lichenized fungi by reviewing current literature, focusing primarily on Ascomycota. While finding and applying the appropriate character sets and analytical tools remains one of the greatest challenges to empirical species delimitation in lichen-forming fungi, the available literature indicates that the inclusion of molecular data in species circumscription is crucial to establish robust hypotheses of species boundaries in this important group of fungi.

The phenotypic features used for distinguishing species within theCladonia furcatacomplex are highly homoplasious

“…In general, it has been shown that in some lichen genera the presence of soredia is a poor diagnostic character (Tehler et al 2004(Tehler et al , 2009Ferencova et al 2010;Lumbsch & Leavitt 2011). …”

The Dynamic Discipline of Species Delimitation: Progress Toward Effectively Recognizing Species Boundaries in Natural Populations

“…This phylogenetic tree-informed approach to assessing species boundaries represents a common practice in studies of lichen-forming fungi. Previously unrecognized species-level clades with corresponding subtle, or overlooked, phenotypic characters have been commonly observed in both crustose lichens [e.g., Acarospraceae (Wedin et al 2009), Graphidaceae (Rivas Plata andLumbsch 2011;Papong et al 2009), Lecanoraceae (Leavitt et al 2011a), Lecideaceae (Ruprecht et al 2010), Mycoblastaceae , and Teloschistaceae (Vondrák et al 2009;Muggia et al 2008)] and foliose and fruticose lichens [e.g., Lobariaceae (Moncada et al 2014;McDonald et al 2003), Parmeliaceae (Leavitt et al 2013a;Wirtz et al 2012;Divakar et al 2005;Molina et al 2004;Kroken and Taylor 2001), Peltigeraceae (O'Brien et al 2009;Goffinet et al 2003), Physciaceae Divakar et al 2007), and Sphaerophoraceae (Högnabba and Wedin 2003)]. As a specific example, Lücking et al (2008) used a combination of medullary chemistry and underside pigmentation in specimens from the Heterodermia obscurata group in Costa Rica to corroborate monophyletic clades in an ITS gene tree as species-level lineages.…”

“…The use of chemistry in lichen taxonomy has been discussed in detail in numerous reviews (Lumbsch 1998a, b;Rogers 1989;Brodo 1986;Egan 1986;Leuckert 1985;Brodo 1978;Hawksworth 1976;Culberson 1969Culberson , 1970), and we refer readers to these valuable sources for a more comprehensive perspective on lichen chemistry. In short, extrolites (secondary metabolites) belong to various classes; the most common and diverse include depsides, depsidones, chlorinated xanthones, and anthraquinones (Lumbsch 2002;Culberson 1969). The presence or absence of specific extrolites, or their replacements by another substance, is widely used to distinguish species, particularly when correlated with differences in geographic distributions.…”

Five new species of Graphidaceae (Ascomycota, Ostropales) from Thailand

“…Indeed, recent phylogenetic studies suggest high amounts of homoplasy in phenotypical characters used to delimit taxa in lichenized fungi (Grube et al 2004;Tehler and Irestedt 2007;Schmitt et al 2009;Rivas Plata and Lumbsch 2011;Lumbsch et al 2014a). Hence, molecular data have greatly increased our ability to identify distinct lineages, including the detection of numerous cryptic lineages (Crespo and Lumbsch 2010;Lumbsch and Leavitt 2011;Leavitt et al 2015). While numerous foliose and fruticose lichen groups have been studied in some detail, especially in the diverse Parmeliaceae, our knowledge on species delimitation in crustose lichens is still in its infancy.…”