title: The Trichoderma harzianum demon: complex speciation history resulting in coexistence of hypothetical biological species, recent agamospecies and numerous relict lineages.
abstract: BACKGROUND
  The mitosporic fungus Trichoderma harzianum (Hypocrea, Ascomycota, Hypocreales, Hypocreaceae) is an ubiquitous species in the environment with some strains commercially exploited for the biological control of plant pathogenic fungi. Although T. harzianum is asexual (or anamorphic), its sexual stage (or teleomorph) has been described as Hypocrea lixii. Since recombination would be an important issue for the efficacy of an agent of the biological control in the field, we investigated the phylogenetic structure of the species.
  
  
  RESULTS
  Using DNA sequence data from three unlinked loci for each of 93 strains collected worldwide, we detected a complex speciation process revealing overlapping reproductively isolated biological species, recent agamospecies and numerous relict lineages with unresolved phylogenetic positions. Genealogical concordance and recombination analyses confirm the existence of two genetically isolated agamospecies including T. harzianum sensu stricto and two hypothetical holomorphic species related to but different from H. lixii. The exact phylogenetic position of the majority of strains was not resolved and therefore attributed to a diverse network of recombining strains conventionally called 'pseudoharzianum matrix'. Since H. lixii and T. harzianum are evidently genetically isolated, the anamorph - teleomorph combination comprising H. lixii/T. harzianum in one holomorph must be rejected in favor of two separate species.
  
  
  CONCLUSIONS
  Our data illustrate a complex speciation within H. lixii - T. harzianum species group, which is based on coexistence and interaction of organisms with different evolutionary histories and on the absence of strict genetic borders between them.
authors.affiliation: Research Area of Gene Technology and Applied Biochemistry, Institute of Chemical Engineering, Vienna University of Technology, Getreidemarkt 9-1665, A-1060 Vienna, Austria. druzhini@mail.zserv.tuwien.ac.at
authors.forename: Irina S
authors.initials: IS
authors.lastname: Druzhinina
authors.forename: Christian P
authors.initials: CP
authors.lastname: Kubicek
authors.forename: Monika
authors.initials: M
authors.lastname: Komoń-Zelazowska
authors.forename: Temesgen Belayneh
authors.initials: TB
authors.lastname: Mulaw
authors.forename: John
authors.initials: J
authors.lastname: Bissett
mesh_terms: D004271:DNA, Fungal / Q000235:genetics; D019143:Evolution, Molecular; D049810:Genetic Speciation; D005828:Genetics, Population; D010802:Phylogeny; D011995:Recombination, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014242:Trichoderma / Q000145:classification / Q000235:genetics*
chemical_list: D004271:DNA, Fungal