The significance of mycorrhizal diversity of trees in the tropical mountain forest of southern Ecuador Abstract

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The significance of mycorrhizal diversity of trees in the tropical

mountain forest of southern Ecuador 


Rootlets were sampled in the mountain rain forest of southern Ecuador from individual trees of 115

species in order to investigate the mycorrhizal state. The results show that the arbuscular

mycorrhization predominates and is independent from the soil type supporting the high diversity of

trees on mineral soil in the ravines as well as on the thick humus layer on the mountain ridge. The

Melastomatacee Graffenrieda emarginata is associated whith arbuscular mycorrhizas and

additionally forms ectomycorrhizas regularly with an ascomycete closely related to the ericoid

mycorrhizal fungus Hymenoscyphus ericae. The latter was shown to mobilize organically bound

nutrients. G. emarginata is the most frequent tree on the mountain ridges where root formation is

restricted to the pure organic soil layer. The ectomycorrhizal state is most probably improving nutrient

uptake from the humus layer and thus supporting the competitiveness of this tree species. One 

Guapira sp. and one Neea sp. (Nyctaginaceae) form ectomycorrhizas with one thelephoraceen

basidiomycete only. Guapira and this Neea species root in the mineral soil of the nutrient rich slopes

and the ecological implication of the ectomycorrhiza is estimated to be low. Another Neea species

forms typical ectomycorrhizas with several basidiomycetes and one ascomycete quite abundantly.

This Neea occurs on the border of the primary forest, along old roadsides and the main river slopes

demonstrating an improved stress resistance by regular ectomycorrhiza formation. Keywords:

arbuscular mycorrhiza, ectomycorrhiza, humus, neotropics, Hymenoscyphus 


Raicillas de 115 especies arbóreas del bosque montano lluvioso en el Sur de Ecuador fueron

muestreadas en orden a investigar su estado de micorrización. Los resultados muestran el dominio

de la micorrización arbuscular siendo independiente al tipo de suelo que soporta la alta diversidad de

árboles en el suelo mineral en las quebradas, así como también en la gruesa capa de humus en la

cima de las cordilleras. La Melastomatacee Graffenrieda emarginata es asociada con arbuscular

micorrizas, y adicionalmente forma ectomicorrizas regularmente con un ascomycete estrechamente

relacionado a el hongo ericoid micorrízico Hymenoscyphus ericae. Este último fue demostrado

movilizar nutrientes orgánicamente unidos. G. emarginata es el árbol más frecuente en la cima de

las montañas donde la formación de las raíces es restringida a la capa de suelo orgánico. El estado

de micorrización probablemente fomenta la absorción de nutrientes desde de la capa de humus y así

mejora la competencia de estas tres especies. Una Guapira sp. y una Neea sp. (Nyctaginaceae)

forman ectomicorrizas solamente con un teleforaceous basidiomiceto. La implicación ecológica de la

ectomicorriza en las raíces de Guapira sp. y Neea sp. en el suelo mineral en pendientes ricas en

nutrientes es estimadamente baja. Otra especie de Neea forma típicas ectomicorrizas con varios

basidiomicetos y un ascomiceto poco abundante. Esta Neea ocurre en el límite del bosque primario,

a lo largo de las orillas de los caminos y en las principales riberas de los ríos demostrando un

mejoramiento a la resistencia a estrés mediante la regular formación de ectomicorriza. Palabras

clave: micorriza arbuscular, ectomicorriza, humus, neotropico, Hymenoscyphus 


The mycorrhizal state of trees largely influences their competitiveness and their integration or

disintegration in the forest community. While symbiotic root-associations with glomeromycete fungi

(arbuscular mycorrhiza) support a community of high diversity, symbiotic associations with basidio- or

ascomycete fungi (ectomycorrhiza) promote monodominant forests (Kottke 2002 and literature

therein). The arbuscular mycorrhiza is the most ancient type (about 400 MA; Taylor et al. 1995) and

is associated with more than 80% of plant species (Smith & Read 1997). The arbuscular mycorrhiza

was replaced several times in a restricted number of plant species by the ectomycorrhial association,

the ericoid or the orchid mycorrhiza, respectively. It was hypothesized that the change from

Lyonia, Volume 7(1), Pages [49-56], December 2004


Ingrid Kottke* & Ingeborg Haug

glomeromycete to asco- or basidiomycete associations was promoted by the seasonal climate

connected to humus accumulation and minimization of water-soluble nutrients especially nitrogen (Read

& Perez-Morena 1993). The predominance of ectomycorrhizal forests in the northern and of arbuscular

mycorrhizal forests in the southern hemisphere could thus be partly explained (Read 1991). Our results

show that the predominating arbuscular mycorrhization in the tropical mountain forest of southern

Ecuador is independent of the amount of humus but is related to phosphate limitation. The investigations

also point out that the replacement of arbuscular mycorrhiza by ectomycorrhiza developed gradually in

the tropics starting with low ecological significance, then promoting few species in the primary forest, and

ending up with the ectomycorrhiza predominance in some secondary forest species.

Materials and Methods

The study site is located on the eastern slope of the Cordillera El Consuelo in the Andes of southern

Ecuador. The territory of about 1000 ha belongs to the Reserva Biológica San Francisco, a protected

area bordering the north of Podocarpus Nationalpark, half way between Loja and Zamora, Loja-Chinchipe

province (3°58´ S, 79°04´ W). Fifteen permanent plots of 400 m2 each were established between 1850

and 2600 m, along the mountain ridge and on the steep slopes of the ravine in the primary mountain rain

forest, and most of the tree species were identified (Homeier et al. 2002). Fine roots were sampled from

115 tree species and the mycorrhizal state was analyzed by conventional methods (Haug and Pritsch

1992; Kottke et al.2004). Arbuscular and ectomycorrhizal fungi were identified from DNA-sequences

(Haug 2002).

Results and Discussion

Nearly all the 115 investigated tree species were found to form arbuscular mycorrhizas (Tab. 1,

Kottke et al. 2004). The results substantiate the hypothesis that the highly diverse tropical forests harbor

arbuscular mycorrhizas (Janos 1987). This mycorrhizal association may be considered as one important

reason for the high diversity of the community because the rather unspecific and multigenomic symbiotic

fungi promote diverse seedlings and adult plants (Smith & Read 1997, Kuhn et al. 2001; Kottke 2002).

The investigations also showed that the arbuscular mycorrhizal state is not restricted to roots in the

mineral soil as was hypothesized by Read (1993), but is the same well developed in the pure humus

layers in the tropical mountain rain forest (Kottke et al. 2004). Phosphate limitation was observed in the

humus layer and is mainly due to fact that phosphate is bound in organic form not available for plant roots

(Wilcke et al. 2001, 2002 and personal communication). Arbuscular mycorrhizal fungi are well known to

mobilize P from the organic fraction improving the P-nutrition of plants significantly (Smith & Read 1997).

Arbuscular mycorrhizas are thus favorable for trees on this stand.

The Melastomatacee Graffenrieda emarginata is regularly found with arbuscular mycorrhizas, but

additionally forms ectomycorrhizas with an ascomycete closely related to the ericoid mycorrhizal fungus 

Hymenoscyphus ericae (Haug et al. 2004). The fungus was shown to mobilize organically bound

nutrients (Read & Perez-Morena 2003 and literature therein). G. emarginata is the most frequent tree

on the mountain ridges where root formation is restricted to the pure organic soil layer. It appears obvious

that the ectomycorrhizal state improves nutrient uptake from the humus layer and thus supports

competitiveness of this tree species (Haug et al. 2004).

Three Nyctaginaceae were found to form ectomycorrhizas, two Neea species and one Guapira

species. On Guapira and on one of the Neea species a variable percentage of rootlets displayed a

special kind of ectomycorrhiza. The ectomycorrhiza development occurs only on the proximal part of the

fine, but long rootlets. Only one fungal species, a Thelephoracee forms the mycorrhizas (Haug et al.

submitted). The Guapira and this Neea species root in the mineral soil of the nutrient rich slopes of

the ravines and the ecological implication of the ectomycorrhiza is estimated to be low. Another Neea

species forms typical ectomycorrhizas with all the absorptive rootlets. The bushy tree is associated with

several basidiomycetes and one ascomycte (Haug et al. submitted). This Neea species occurs on the

border of the primary mountain forest, along old roadsides and along the main river slopes in disturbed

places where it forms a superficial, dense mat of ectomycorrhizal roots. The ectomycorrhizal state most

probably improves drought resistance and competitiveness against Pteridium arachnoideum, 

Chusquea spp. and other grasses. 

Lyonia, Volume 7(1), Pages [49-56], December 2004

El significado de la diversidad de micorrizas de arbolesen el bosque montanoso lluvioso en el Sur de Ecuador


The investigation revealed that the mycorrhizal state of a tree poses a selective ecological pressure

that cannot be ignored when species are selected for tree plantations and regeneration of tropical

mountain forests. The mycorrhizal state also determines the root system development (Brundrett 2002). 

Guapira sp., as most of the other arbuscular mycorrhizal trees, has regularly branched, long fine

roots with many root hairs that are only suppressed in the proximal part of roots that are transformed into

ectomycorrhizas. G. emarginata displays an irregularly branched root system with rather short fine

roots that have no root hairs (Haug et al. 2004). The ectomycorrhizal Neea species forms densely

branched mats of short roots that are typical for ectomycorrhizal trees (Feil et al. 1988). 

No other Melastomataceae was so far shown to form ectomycorrhizas with the ascomycete related to 

H. ericae. However, this fungal aggregate is spread world wide and associated with several

ectomycorrhizal trees, ericaceous plants and hepatics occurring on acidic, humus-rich soils (Vrålstadt et

al. 2000, 2001; Haug et al. 2004). Investigations are currently carried out to clarify if the fungal associate

of G. emarginata is present in ericaceous plants and hepatics of the neotropical mountain forest. The

latter could have served and still may serve as vectors for fungus distribution. The two Nyctaginaceen

species Guapira sp. and Neea sp., positioned within a family that is mainly known from South

America and contains mostly non-mycorrhizal plants (Brundrett 2002) have some ectomycorrhizal

relatives in Peru (Neea sp.; Alexander and Högberg 1986), the Amazon forest near Manaus (Neea

sp.; Singer 1979) and the Amazon valley in the south of Venezuela (Neea obovata, N. robusta,

Guapira sancarlosiana; Moyersoen 1993). In the latter habitat all three species harbored arbuscular

and ectomycorrhiza forming fungi and are large, dominating trees there. The ectomycorrhizal fungi

connected to the trees in these habitats have not been identified, and it will be interesting to discover how

close they are related to the Ecuadorian species. This knowledge could provide us with further

information about the paleo-biogeography of the northern Andes, and may substantiate the hypothesis

that lowland trees were more widely distributed in the Andes during the late Tertiary (van der Hammen &

Cleef 1986; Taylor 1995). Guapira sp. and Neea sp. could by relicts from these times. 


The research was generously supported by the German Science Foundation (DFG project FOR 402).

We thank the Fundacíon Científica San Francisco for providing research facilities and the Universidad

Técnica Particular de Loja (UTPL) for kind personal help and access to laboratories. 


Alexander, I.J. & P. Högberg. 1986. Ectomycorrhizas of tropical angiospermous trees. The New 

Phytologist 102, 541-549

Brundrett, M.C. 2002. Coevolution of roots and mycorrhizas of land plants. New Phytologist 154:


Feil, W.; I. Kottke & F. Oberwinkler. 1988. The effect of drought on mycorrhizal growth and very fine

root systems of Picea abies (L.) Karst. under natural and experimental conditions. Plant and Soil 108: 


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Progress 1: 167-178

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of southern Ecuador. New Phytologist

Haug I.; J. Lempe; J. Homeier; M. Weiß; S. Setaro; F. Oberwinkler & I. Kottke. 2004. Graffenrieda 

emarginata (Melastomataceae) forms mycorrhizas with Glomeromycota and with a member of 

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Regenwald der Estación Cientifíca San Francisco in Südecuador. Berichte der Reinhessischen

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dominant in the organic soil of a neotropical montane cloud forest. J. Trop. Ecol. 20: 125-129

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symbiotic associations with hepatics: Jungermanniales have sebacinoid mycobionts while Aneura 

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mycorrhizal fungi. Nature 414: 745-748

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Sur de Venezuela. Scientia Guaianae 3:, 83 pp. Caracas

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towards relevance? New Phytologist 157: 475-492.

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Amazonica 9: 25-41.

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organic layers under tropical montane rain forest in Ecuador. European J Soil Science 53: 15-27

Table 1 Investigated tree species of the mountain rain forest in southern Ecuador: All species form

mycorrhizas, those in bold form ectomycorrhizas ECM, the others form arbuscular mycorrhizas.

Table 1. Arboles Investigados en tres bosques lluviosos en el sur de Ecuador: Todas las especies

forman micorrizas, las que estan en negrita forman ectomicorrizas ECM, las otras forman micorrizas 







Alzatea verticillata 


Guarea cf. kunthiana 


Tapirira guianensis 

Guarea pterorhachis 

Tapirira obtusa 


Inga cf. acreana 

Lyonia, Volume 7(1), Pages [49-56], December 2004

El significado de la diversidad de micorrizas de arbolesen el bosque montanoso lluvioso en el Sur de Ecuador




Inga striata 


Guatteria cf



Siparuna aspera 


Ilex cf. amboroica 


Coussapoa villosa 


Dendropanax sp. 

Ficus cf. subandina 

Schefflera sp. 

Helicostylis tovarensis 




Morus insignis 

Euterpe catinga 

Euterpe precatoria 

Naucleopsis glabra 


Critoniopsis floribunda 

Pseudolmedia rigida 

Piptocoma discolor 


Myrsine coriaceae 


Tabebuia chrysantha 

Myrsine latifolia 


Cecropia gabrielis 


Calyptranthes sp. 




Eugenia sp. 



Eugenia valvata 



Myrcia sp. 

Chrysobalanaceae  Hirtella cf. pilosissima 

Myrcianthes myrsinoides 


Clethra revoluta 


Guapira sp ECM Neea species (1

ECM Neea species (2ECM 


Clusia sp. (2 species) 


Piper perareolatum 

Tovomita weddeliana 

Piper sp. (4 species indet.) 

Vismia tomentosa 

Podocarpaceae  Podocarpus oleifolius 




Podocarpus sprucei 

Weinmannia pinnata 

Prumnopity montana 




Quiina sp. 

Weinmannia spruceana  Rosaceae 

Prunus opaca 

Lyonia, Volume 7(1), Pages [49-56], December 2004


Ingrid Kottke* & Ingeborg Haug


Purdiaea nutans 


Dioicodendron dioicum 


Sloanea sp. 

Elaeagea karstenii 


Alchornea cf. grandis 

Elaeagia pastoensis 

Alchornea pearcei 

Faramea glandulosa cf. uniflora 

Alchornea sp

Faramea uncinata 

Hyeronima asperifolia 

Faramea cf. uniflora 

Hyeronima cf. duquei 

Isertia laevis 

Hyeronima moritziana 

Ladenbergia oblongifolia 

Hyeronima cf. oblonga 

Macrocnemum cf. roseum 


Aniba cf. muca 

Palicourea angustifolia 

Cinnamomum sp. 

Palicourea andaluciana 

Nectandra cf. acutifolia 

Palicourea canarina 

Nectandra crassiloba 

Palicourea luteonivea 

Nectandra lineatifolia 

Palicourea stenosepala 

Nectandra subbullata 

Psychotria sp. 

Ocotea cf. aciphylla 

Psychotria tinctoria 

Ocotea benthamiana 


Meliosma sp. 


Talauma caricifragrans 


Matayba sp. nov. 


Byrsonima cf. 



Micropholis guyanensis 



emarginata ECM 

Pouteria austin-smithii 

Meriana drakei 


Cestrum schlechtendahlii 

Meriana hexamera 

Solanum nutans 

Meriana rigida 


Symplocos peruviana 

Meriana sp. nov. 


Heliocarpus americanus 

Miconia cf. calophylla 


Ternstroemia cf. jelskii 

Miconia crebribullata 

Miconia jahnii 

Lyonia, Volume 7(1), Pages [49-56], December 2004

El significado de la diversidad de micorrizas de arbolesen el bosque montanoso lluvioso en el Sur de Ecuador


Miconia punctata 

Miconia rigida, Miconia 



Lyonia, Volume 7(1), Pages [49-56], December 2004


Ingrid Kottke* & Ingeborg Haug

Document Outline

  • The significance of mycorrhizal diversity of trees in the tropical mountain forest of southern Ecuador
    • Abstract
    • Resumen
    • Introduction
    • Materials and Methods
    • Results and Discussion
    • Acknowledgements
    • References

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