**3.** *Trichoderma:* **distribution and biogeography**

Broad studies on the taxonomy and biodiversity of *Trichoderma* have been carried out in North America and some regions of Europe (*e.g*. Bissett 1991a,b,c, 1992), where the distribution of species is now reasonably well known, particularly for specific taxa or groups (Lieckefeldt et al., 2001). Some regions have been studied in detail, e.g. Wuczkowski et al., 2003, investigated the genetic diversity of a European river-floodplain landscape near Vienna, and Migheli et al., 2009 studied the biodiversity of *Trichoderma* in Sardinia, a Mediterranean hot spot of biodiversity, analyzing the influence of abiotic factors on the distribution of species *Trichoderma.* In the latter study, 482 strains of *Hypocrea/Trichoderma* were identified from undisturbed and disturbed environments (forest, shrub lands and undisturbed or extensively grazed grass steppes), with the finding that most of the strains were pan-European and/or pan-global species. Meinke et al., 2010 described the *Trichoderma* communities in rhizosphere of four varieties and transgenic lines of potato in Germany. They observed a heterogeneous distribution and varying diversity of *Trichoderma* dependent on soil characteristics, climate and management practices, in this case not related to the crop variety.

Studies in previously uninvestigated regions or habitats have frequently led to the discovery of new taxa. Kullning et al. (2000) examined 76 isolates from Russia, Nepal and North India, reporting seven species (*T. asperellum, T.atroviride, T. ghanense, T. hamatum, T. harzianum, T. virens* and *T. oblongisporum*) and five new taxa. They also found T. *harzianum* the most genetically diverse speices, with the *T. harzianum* complex representing the majority of isolates. A similar study was conducted by Kubicek et al. (2003) in Southeast Asia, where they reported *T. asperellum, T.atroviride, T. ghanense, T. hamatum, T. harzianum, T. koningii, T. spirale, T. virens, T. viride* and *H. jecorina* (anam: *T. reesei*), along with seven new species

Biodiversity of *Trichoderma* in Neotropics 309

orchards, coffee, beans, cotton, flowers and rubber tree plantations, (Castro, 1996, Carsolio *et al*., 1994, Hebbar *et al*., 1999; Hoyos-Carvajal et al., 2008; Rivas & Pavone, 2010; Samuels *et al*, 2000, Samuels *et al.,* 2006, ), to control the symbiotic fungus of the leaf-cutting ant *Atta cephalotes* (López & Orduz, 2003), as well as to study the ability of *Trichoderma* to improve plant vigour and stimulate crop growth (Bae et al., 2009, Hoyos-Carvajal et al.,

Our knowledge of the distribution of *Trichoderma* species is constantly evolving in the context of current advances toward resolving the taxonomy of the genus. As a consequence, we can anticipate in future years to better understand the biogeography of *Trichoderma* species as research is pursued in new regions and to resolve complex species aggregates. For example, Samuels et al. (2006) determined that the species commonly cited in literature, *Trichoderma koningii,* in the strict sense is a relatively uncommon species restricted to temperate Europe and North America. From within the *T. koningii* aggregate he erected numerous new species, describing *T. caribbaeum* var*. aequatoriale, T. koningiopsis,* and *T. ovalisporum* as endophytes of *Theobroma* species in tropical America, and *T. ovalisporum* also from the woody liana *Banisteropsis caapi* in Ecuador. *T. koningiopsis* (previously identified as *T. koningii*) was determined to be common in tropical America, occurring also on natural substrata in East Africa, Europe and Canada, from ascospores in eastern North America, and as an endophyte in *Theobroma. T. stilbohypoxyli*, described as a parasite of *Stilbohypoxylon* species in Puerto Rico, was found to be more common in the tropics. Samuels et al. (1998) reported on the diversity of *Trichoderma* section *Longibrachiatum,* revealing diversity in neotropical areas resulting in the description of new species in this section. Jaklitsch et al. (2006), in revising the *T. viride* species complex, reported *T. viridescens* as a species found in Peru at high elevation, and *T. neokoningii* in a tropical region in Peru. He also described, as new species, *T. scalesiae* isolated as an endophyte from the trunk of daisy tree (*Scalesia pedunculata*) in the Galapagos Islands of Ecuador, *T. paucisporum* as a mycoparasite of *Moniliophthora roreri* on pods of *Theobroma cacao* in Ecuador, and *T. gamsii*, an apparently cosmopolitan species that has been found in Italy, Rwanda, South Africa, and Romania as well as Guatemala. Recent studies undertaken to find biocontrol agents in specific crops such as cocoa also has resulted in the determination of other new species in neotropical

regions (Jaklitsch et al., 2006, Samuels et al., 2000, Samuels et al., 2006).

**4.1 Can we generalize on the soil-inhabiting species of** *Trichoderma* **occurring in the** 

Hoyos-Carvajal et al. (2009a) carry out a systematic survey of *Trichoderma* species in seven countries: Mexico, Guatemala, Panama, Peru, Ecuador, Brazil and Colombia, isolating primarily from soil and employing complementary observations on morphology, metabolism and sequences of ITS 1 and 2 and the 5' region of *tef*-1a encompassing four introns. They identified 182 *Trichoderma* isolates finding a wide diversity of species over this region of the neotropics - *T. asperellum* (26 isolates), *T. asperelloides* (34 isolates, as *T. asperellum* 'B') *T. atroviride* (3), *T. brevicompactum* (5), *T. crassum* (3), *T. erinaceum* (3), *T. gamsii* (2), *T. hamatum* (2), *T. harzianum* (49), *T. koningiopsis* (6), *T. longibrachiatum* (3), *T. ovalisporum* (1), *T. pubescens* (2), *T. rossicum* (4), *T. spirale* (1), *T. tomentosum* (3), *T. virens* (8), *T. viridescens* (7), *T. parareesei* (3, as *H. jecorina*), along with 11 presumptive new species that have not yet been described. Analyses of variance were performed on metabolic data for the Colombian isolates. Highly significant differences (P < 0.0001) in assimilation were observed for 42 substrates among the 12 species isolated from Colombia (*T. asperellum*, *T. atroviride*, *T.* 

2009b, Resende et al., 2004).

**neotropics?** 

among 96 isolates tested (Bissett et al., 2003). The *T. harzianum* complex was equally prevalent, exhibiting high metabolic and morphological variability that may explain the wide distribution of this species aggregate over different habitats (Kubicek et al., 2003).

Sadfi-Zouaoui et al., 2009, in a study encompassing four different bioclimatic zones in Tunisia, assessed the genetic diversity of endemic species of *Trichoderma* and their association to bioclimatic zones. *T. harzianum*, divided into six clades, was the prevalent species complex. *T. harzianum* and *T. longibrachiatum* were predominant in forest soils in north Tunisia; *T. harzianum, T. saturnisporum* and *Trichoderma* sp. indet. were isolated from forest soils in central Tunisia; *T. atroviride* and *T. hamatum* were found in cultivated fields in northeast Tunisia; and *T. harzianum* and *T. hamatum* were present in oasis soils in south Tunisia. Zhang et al. (2005) assessed the biodiversity and biogeography of *Trichoderma* in China, sampling four disparate regions: north (Hebei province), south-east (Zhejiang province), west (Himalayan, Tibet) and south-west (Yunnan province). *T. asperellum, T. koningii, T. atroviride, T. viride, T. velutinum, T. cerinum, T. virens, T. harzianum, T. sinensis, T. citrinoviride,* and *T. longibrachiatum* were identified along with two putative new species. This study revealed a north-south gradient in species distribution in eastern Asia. Tsurumi et al. (2010) explored the biodiversity of *Trichoderma* in Mongolia, Japan, Vietnam and Indonesia, isolating 332 strains and finding T*. harzianum, T. hamatum, T. virens* and *T. crassum* in most habitats. *T. koningiopsis, T. atroviridae* and *T. stramineum* also were frequently isolated, except in cool sites where they were replaced by *T. polysporum* and *T. viridescens.* In tropical areas *T. ghanense, T.brevicompactum* and *T. erinaceum* were prevalent. In addition they discovered five unidentifiable isolate groups and 26 singular unidentified strains.

The most comprehensive survey over any one biogeographic region was performed by Jaklitsch (2009, 2011). He employed three genetic markers to identify 620 specimens of *Hypocrea* occurring in 14 countries in temperate regions of Europe, identifying 75 species including 29 previously undiscovered, thus greatly expanding the number of species known in that region. His observations suggest that the biodiversity of *Hypocrea/Trichoderma* above soil exceeds the diversity residing in soil. He also speculated that the majority of species may be nectrotrophic on other fungi colonizing wood and bark. It now appears that the majority of *Trichoderma* species are capable of sexual recombination and form a teleomorph, and a comparatively smaller number may be clonally propagating agamospecies.

As a result of these recent discoveries, generalizations on the distribution of *Trichoderma*  have become increasingly problematic. Their occurrence will be modulated by microclimatic components, substrate availability, rhizosphere associations, soil chemistry, complex ecological interactions and many other factors. The introduction of invasive species, biocontrol agents, and agricultural perturbations result in changes in specific patterns of distribution that cannot be clearly identified, as suggested by Migheli et al. (2009) in finding the colonization of pan-European pan-global *Hypocrea/Trichoderma* species on the island of Sardinia, which may or may not involve the displacement of native strains.
