Not as ubiquitous as we thought: taxonomic crypsis, hidden diversity and cryptic speciation in the cosmopolitan fungus Thelonectria discophora (Nectriaceae, Hypocreales, Ascomycota)

Authors: SALGADO-SALAZAR, CATALINA - University Of Maryland; Rossman, Amy; CHAVERRI, PRISCILA - University Of Maryland

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2013
Publication Date: 10/18/2013
Publication URL: http://DOI: 10.1371/journal.pone.0076737
Citation: Salgado-Salazar, C., Rossman, A.Y., Chaverri, P. 2013. Not as ubiquitous as we thought: taxonomic crypsis, hidden diversity and cryptic speciation in the cosmopolitan fungus Thelonectria discophora (Nectriaceae, Hypocreales, Ascomycota). PLoS One. 8(10). DOI: 10.1371/journal.pone.0076737.

Interpretive Summary: Fungi are a large and diverse group of organisms that cause serious diseases of crop and forest plants. Accurate knowledge of these fungi is critical for controlling the diseases they cause. Although some fungal species are thought to be widely distributed, increasingly research is showing that what was considered to be one species may actually be a number of different species that look very similar; these are known as cryptic or hidden species. Such is the case with a seemingly ubiquitous species that occurs widely on hardwoods such as cacao and rubber in tropical regions. In this research numerous specimens of this species were analyzed. It was determined that what was considered one species is actually sixteen different species. Each cryptic species has a slightly different appearance and biology i.e. some are plant pathogenic while others are not. Knowing the difference is important in preventing the movement of these plant pathogens. This research will help plant quarantine officials prevent the spread of noxious plant diseases and provide the basis for plant pathologists to accurately identify the cause of diseases of important crop plants.

Technical Abstract: The distribution of microbial species, including fungi, has long been considered cosmopolitan. Recently, this perception has been challenged by molecular studies in historical biogeography, phylogeny and population genetics. Here we explore this issue using the fungal morphological species Thelonectria discophora, one of the most common species of fungi in the family Nectriaceae, encountered in almost all geographic regions and considered a cosmopolitan taxon. In order to determine if T. discophora is a single cosmopolitan species or an assemblage of sibling species, we conducted various phylogenetic analyses, including standard gene concatenation, Bayesian concordance methods, and coalescent-based species tree reconstruction on isolates collected from a wide geographic range. Results show that diversity among isolates referred as T. discophora is greatly underestimated and that it represents a species complex. Within this complex, sixteen distinct highly supported lineages were recovered, each of which has a restricted geographic distribution and ecology. The taxonomic status of isolates regarded as T. discophora is reconsidered, and the assumed cosmopolitan distribution of this species is rejected. We discuss how assumptions about geographically widespread species have implications regarding their taxonomy, true diversity, biological diversity conservation, and ecological functions.