Mycol. Res. 108 (3): 325–336 (March 2004). f The British Mycological Society 325 DOI: 10.1017/S0953756204009396 Printed in the United Kingdom. Comparative studies on microfungi in tropical ecosystems in Ivory Coast forest litter : behaviour on different substrata Angelo RAMBELLI1*, Bonaria MULAS2 and Marcella PASQUALETTI1 1 Dipartimento di Ecologia e Sviluppo Economico Sostenibile, Università della Tuscia, 01100, Viterbo, Italy. Dipartimento di Botanica ed Orto Botanico, Università di Cagliari, 09100, Cagliari, Italy. E-mail : rambelli@unitus.it 2 Received 1 October 2002; accepted 17 December 2003. Fungal colonies sporulating on 71 kinds of leaves that fell during the dry season in the Tai National Park (Ivory Coast) were analysed. A consistent connection between certain fungal species and their substrata was detected among the 184 fungal species that were identified. Each fungal species was characterized according to morphological and ecological features. Multidimensional scaling showed that certain ubiquitous and common species have morphological characters distinguishing them from specialised species. INTRODUCTION Many studies have been published on the ecology of fungi in tropical forest litter and the identification of specific fungal communities (Subramanian & Vittal 1974, Rambelli et al. 1983, 1984, 1991, Mercado-Sierra 1984, Bills & Polishook 1994, Lodge & Cantrell 1995, Læssøe et al. 1996, Matsushima 1971–96, Polishook, Bills & Lodge 1996, Lodge 1997, Calduch et al. 2002). Such studies often resulted in discovery of new fungal taxa (Rambelli & Ciccarone 1985, Mercado-Sierra, Holubová-Jechová & Mena Portales 1997, CastañedaRuiz, Saikawa & Guarro 1999, Pasqualetti & Rambelli 1999, Siboe, Kirk & Cannon 1999, Calduch et al. 2002). Other investigations have focused on possible specialisation among saprotrophs (Pirozynski 1972, Subramanian & Vittal 1979, 1980, Kabi Ouanyou & Rambelli 1990, Læssøe & Lodge 1994, Lodge & Cantrell 1995, Lodge & Læssøe 1995, Mulas & Rambelli 1995, Lodge, Fisher & Sutton 1996, Polishook et al. 1996, Lodge 1997, Pascholati, Piccolo Grandi & Milãnez 2001). Recently, analysis of the microfungi colonising different litter species in natural Mediterranean ecosystems has been extended to assess both the number of colonies per surface unit and the type of optimal and adaptive colonisation (Mulas, Pasqualetti & Rambelli 1995, Pasqualetti, Ialongo & Rambelli 1995). This has increased our knowledge of ecological characters of * Corresponding author. particular fungal species and has shed light on their roles in differential colonisation and decomposition of plant debris. In this study, we analysed microfungi sporulating on incubated dead leaves in the Tai National Park in the Ivory Coast in order to detect differential effects exerted by the litter of different plant species. MATERIALS AND METHODS Description of the study area The study area is part of the Tai National Park located in the south-western region of the Ivory Coast. The 360 000 ha Park is covered by native forest, a subhygrophilous forest representative of the EremospatoMabetum vegetation type (Huttel 1975). Rambelli et al. (1983) published an inventory of the plant families forming the Park’s vegetation. The park lies in the drainage basin of the Cavally river that forms the border between Ivory Coast and Liberia. The undulating terrain reaches about 350 m a.s.l. at some points. The soils are mainly saturated ferrallithic with a fine sandy surface structure. The litter layer is thin (3–4 cm deep) and discontinuous, since wind and rain tend to concentrate the litter into pockets where it mineralises rapidly due to high temperature and humidity that favour microbial growth. The climate of the area can be defined as humid, megathermic, with a very low moisture deficit over the year (Rambelli et al. 1983). Annual temperature Microfungi in tropical forest litter variation is low. Daily temperatures range from a maximum of 27.9 xC in April to a minimum of 25.1 x in July–August, with a mean of 26.4 x. Yearly rainfall ranges from 1500–2000 mm yrx1 and is seasonal. The dry season runs from December to February, and the rainy season comprises the remaining eight months of the year with the exception of two dry weeks in August. Relative atmospheric humidity ranges from 50–75 % during the day, with peaks of over 90 % at night. Sampling Samples were collected yearly in January 1992–95 during the dry season (Dec.–Feb.). Neither senescent freshly shed leaves nor highly decayed leaves of uncertain identity were included in the samples. This resulted in samples that were as homogeneous and comparable as possible. The litter samples for each plant species were placed in sterile paper bags, and were identified by Laurent Ake Assi (Director, Centre National de Floristique, Abidjan University, Ivory Coast). Fifteen damp chambers were set up for each substratum to allow direct observation, collection, and determination of the fungal species. Voucher specimens are deposited in the ROHB herbarium in Rome. Characterisation of the fungi Some ecological and taxonomic characteristics were recorded for each fungal species. The ecological characters were classified as follows : S, specialised species present on one or two substrates ; C, common species present on three to ten substrata ; or U, ubiquitous species present on more than ten substrata. The fungi were also categorized according to the following morphological features based on direct observations and confirmed by bibliographic data ; HC, hyaline conidia ; PG, pigmented conidia ; UC, unicellular conidia ; SC, septate conidia ; LP, low conidial production ; AP, abundant conidial production ; PC, phialidic conidiogenesis ; PE, percurrent conidiogenesis; SY, sympodial conidiogenesis ; SS, presence of sterile setae ; and SA, absence of sterile setae. Data analysis Data were analysed using an ordination method to reduce the dimensionality, in which the original n variables are replaced by artificial variables in an attempt to achieve a more efficient representation of data in few dimensions (Podani 1994). The multidimensional scaling method (MDS) was employed, which does not assume linear relationships between variables ; an input matrix of normalised Euclidean distances was utilised (Wilkinson, Hill & Vang 1992). Chi-square tests were performed between all variables to determine if the MDS grouped characters were significantly correlated. The table showing the results was ordered using the block clustering method. The rearrangement of the 326 data matrix is based on the assumption that the rows and columns are classifiable into groups. Matrix rearrangement is useful in fungal ecology such as when explaining classification of fungal communities in terms of species groups and visa versa (Podani 1994). The 23 ubiquitous fungal species (occurring on more than ten leaf species) were analysed further. For each species pair we determined whether the fungal species occurred together randomly on the same substratum, or whether they were positively or negatively associated with each other. The Yule association index (Q) and the asymptotic standard error were calculated, followed by chi-square test to determine whether the Q values were significantly different from 0 at P<0.01 (Wardle & Parkinson 1991, Wilkinson, Hill & Vang 1992). Cluster analysis (Euclidean distance, Ward’s method) was also performed. RESULTS Leaves were collected from 71 plant species representing 58 genera and 32 families (Table 1). The most frequent families included the Leguminosae (12 species), Euphorbiaceae (7), Ebenaceae (5), and Annonaceae (4) (Table 1). Overall, 184 fungal species belonging to 96 genera were observed and identified (Table 2). The species in Table 2 were ordered using the block clustering method. Five groups of fungal species (A–E) and six groups of plant substrata (1–6) can be distinguished. The first fungal group (A) contains species found on more than one leaf type : these species were present in substratum groups 1–3 and were more sporadic in the others. Fungal species with a more specialized behaviour or those present on few substrata can be seen in the central part of the Table (B and C). B contains the fungal species predominantly associated with sector 1, and in particular leaves of Memecylon lateriflorum, Caloncoba brevipes, and Uapaca guinee¨nsis. C contains the largest number of species where several specialised associations between groups of fungal species and certain plant substrata can be distinguished. The highest proportion of specialised associations (66) was observed in sectors 1 and 2, while sporadic specialised relationships involving uncommon or rare fungi were also detected in the other sectors. The greatest number of specialised species was found on Newtonia duparquetiana, which can mainly be ascribed to the occurrence of several species of Sporidesmium (Table 2). This substratum hosts 21 specialised fungi. Another association with a particularly high number of species was recorded in sector 1 C on Diospyros sanza-minika, and in sector 2 C on Xylopia aethiopica and Allanblackia floribunda. Only 16 fungal species with ubiquitous behaviour appeared in sectors D and E. In D they were particularly abundant in substratum groups 1 and 2, whereas the species in sector E showed a more uniform pattern and were also present in 3, 4, 6 (Table 2). Investigations were carried out to find a possible correlation between the fungal species present on one A. Rambelli, B. Mulas and M. Pasqualetti 327 Table 1. List of substrata with symbols, year of collection, and voucher specimen reference numbers. Year Leaf species Family Matrix symbols Voucher specimens 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 Anthonotha fragrans Berlinia occidentalis Dialium aubrevillei Dichapetalum toxicarium Diospyros cooperi Diospyros gabunensis Duboscia viridiflora Ficus vogeliana Gilbertiodendron limba Memecylon lateriflorum Neuropeltis prevosteoides Scytopetalum tieghemii Tarrietia utilis Terminalia superba Trichoscypha chevalieri Uapaca esculenta Uvaria angolensis Xylopia acutiflora Leguminosae Leguminosae Leguminosae Chailletiaceae Ebenaceae Ebenaceae Tiliaceae Moraceae Leguminose Melastomataceae Convolvulaceae Scytopetalaceae Sterculiaceae Combretaceae Anacardiaceae Euphorbiaceae Annonaceae Annonaceae aa by p m n ae bl u aw r ao o am j bn av x ah ROHB 405 ROHB 406 ROHB 407 ROHB 408 ROHB 409 ROHB 410 ROHB 411 ROHB 412 ROHB 413 ROHB 414 ROHB 415 ROHB 416 ROHB 417 ROHB 418 ROHB 419 ROHB 420 ROHB 421 ROHB 422 1993 1993 1993 1993 1993 1993 1993 1993 1993 1993 1993 1993 1993 1993 Alchornea cordifolia Bridelia grandis Cleistopholis patens Didelotia idae Diospyros mannii Drypetes aylmeri Grewia barombiensis Harungana madagascariensis Hypselodelphys violacea Landolphia owariensis Memecylon afzelii Memecylon donianum Newtonia duparquetiana Sacoglottis gabonensis Euphorbiaceae Euphorbiaceae Annonaceae Leguminosae Ebenaceae Euphorbiaceae Tiliaceae Hypericaceae Marantaceae Apocynaceae Melastomataceae Melastomataceae Leguminosae Humiriaceae bu t ak bg bd a s bx ad ap d be bt aq ROHB 423 ROHB 424 ROHB 425 ROHB 426 ROHB 427 ROHB 428 ROHB 429 ROHB 430 ROHB 431 ROHB 432 ROHB 433 ROHB 434 ROHB 435 ROHB 436 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994 1994 Allanblackia floribunda Caloncoba brevipes Chrysophyllum taiense Diospyros kamerunensis Irvingia gabonensis Lophira alata Lovoa trichilioides Macaranga heterophylla Piptadeniastrum africanum Santalodes afzelii Thaumatococcus daniellii Trichoscypha arborea Xylopia aethiopica Guttiferae Flacourtiaceae Sapotaceae Ebenaceae Simaroubaceae Dipterocarpaceae Meliaceae Euphorbiaceae Leguminosae Connaraceae Scitamineae Anacardiaceae Annonaceae ar as g bp an at au z aj e bv al ac ROHB 437 ROHB 438 ROHB 439 ROHB 440 ROHB 441 ROHB 442 ROHB 443 ROHB 444 ROHB 445 ROHB 446 ROHB 447 ROHB 448 ROHB 449 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 1995 Bambusa vulgaris Beilschmiedia mannii Calpocalyx aubrevillei Calpocalyx brevibracteatus Canthium rubens Combretum dolichopetalum Corynanthe pachyceras Coula edulis Decorsella paradoxa Dictyophleba leonensis Diospyros sanza-minika Ficus sagittifolia Guarea thompsonii Hannoa klaineana Homalium aylmeri Landolphia hirsuta Leptoderris cyclocarpa Manniophyton fulvum Newtonia aubrevillei Parinarium excelsum Pentaclethra macrophylla Pseudospondias microcarpa Strephonema pseudo-cola Symphonia globulifera Tetracera potatoria Uapaca guinee˘nsis Gramineae Lauraceae Leguminosae Leguminosae Rubiaceae Combretaceae Rubiaceae Olacaceae Urticaceae Apocynaceae Ebenaceae Moraceae Meliaceae Simaroubaceae Flacourtiaceae Apocynaceae Leguminosae Euphorbiaceae Leguminosae Rosacea Leguminosae Anacardiaceae Combretaceae Guttiferae Dilleniaceae Euphorbiaceae bw bi l c ai ag q f bf af i br bh h az bs w b ay y bc bm ab ba k v ROHB 450 ROHB 451 ROHB 452 ROHB 453 ROHB 454 ROHB 455 ROHB 456 ROHB 457 ROHB 458 ROHB 459 ROHB 460 ROHB 461 ROHB 462 ROHB 463 ROHB 464 ROHB 465 ROHB 466 ROHB 467 ROHB 468 ROHB 469 ROHB 470 ROHB 471 ROHB 472 ROHB 473 ROHB 474 ROHB 475 Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 bt a bg aw aq r as v i ac ar bm bi br af j ak bl aa c g b p k bd bc ay d at f q be z ae w an y l m ao ad s ai h bn az e aj bu by am bf ah bx bw bs al bp ag av o ap n ba ab u x t bh au bv X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Group A X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Group B X X X X X X X X X X X X X X X X X X X X X X X X X X Group C X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 16 14 15 14 12 10 7 4 4 7 7 3 5 9 4 5 6 6 5 5 9 8 11 13 10 10 1 1 1 1 1 1 7 4 2 1 1 2 1 7 5 4 3 2 3 4 4 3 4 4 7 7 10 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 2 2 2 1 1 1 1 1 1 328 Matrix groups Symbols of matrices Pseudobotrytis terrestris Chaetosphaeria vermicularioides Chalara alabamensis Cryptophiale kakombensis Cryptophiale udagawae Dictyochaeta assamica Phaeoramularia hachijoensis Corynespora elaeidicola Sporidesmium parvum Brooksia tropicalis Kylindria keitae Hansfordia pulvinata Pseudocochliobolus eragrostidis Beltrania onirica Sporidesmium sp. 1 Periconia minutissima Melanopsammella chloroconica Periconia byssoides Zygosporium minus Idriella tropicalis Selenosporella curvispora Rhinocladiella ellisii Gyrothrix magica Idriella fertilis Hansfordiellopsis lichenicola Kramasamuha sibika Stachybotrys kampalensis Hansfordiellopsis aburiensis Anungitea fragilis Gyrothrix grisea Solosympodiella clavata Ulocladium consortiale Dictyochaetopsis intermedia Sporidesmium tropicale Sporidesmium ghanaense Beltrania africana Cordana pauciseptata Alternaria alternata Kiliophora ubiensis Ardhachandra cristaspora Zanclospora indica Chaetosphaeria innumera Tripospermum myrti Torula herbarum Idriella lunata Calcarisporium acerosum Sporidesmium njalaense Circinotrichum papakurae Chaetopsina fulva Speiropsis pedatospora Parasympodiella laxa Arthrinium phaeospermum Stachybotrys parvispora Sporidesmium sp. 5 Sporidesmium jasminicola Minimidochium setosum Helicosporium MCF 1847 Dictyopolyschema sp.1 Acrodictys erecta Deightoniella jabalpurensis Gyrothrix circinata Hyphodiscosia jaipurensis Sporidesmium adscendens Sporidesmium nodipes Sporidesmium sp. 6 Subulispora procurvata Sporidesmium afrormosiae Geotrichum candidum Curvularia ovoidea Chaetendophragmia triangularis var. africana Articulospora foliicola Blastophorum uniseptatum Chalara microspora Dactylaria sp. 1 Pseudospiropes simplex Zygosporium oscheoides Venturia carpophila Spiropes clavatus Spiropes guareicola Spegazzinia tessarthra Flosculomyces floridaensis Phialocephala sp. 1 Sporidesmium penzigii Bipolaris indica Circinotrichum rigidum Cladosporium chlorocephalum Endophragmia brevis Sporidesmium sp. 2 Microfungi in tropical forest litter Table 2. Presence of 184 fungal species on 71 substrata; the table is ordered by the block clustering method ; principal groups of fungal species and substrata are separated. Symbols of matrices bt a bg aw aq r as v i ac ar bm bi br af j ak bl aa c g b p k bd bc ay d at f q be z ae w an y l m ao ad s ai h bn az e aj bu by am bf ah bx bw bs al bp ag av o ap n ba ab u x t bh au bv X X X X X X X X X X X X X X X X X X X X X X X X Group C X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 28 X X X X X X X X X X X X X X X X 29 38 X X X X X X X X X X X X X X X X 49 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 51 21 20 20 19 X X X X X X X X X X X X X X X X X X X X X X X X X 13 13 X X X X X X X 10 14 X X X X X X X X X X X X X X X X X X X X X X X 22 20 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 18 22 26 X X X X X X X X X X X X X X X X X X X X X X X X 12 X X X X X 10 X X X X X 17 X X X X X X X X X X X X X X X X X X X X X X X 19 19 13 6 7 4 7 X X X X X X X X X X X X X X X X X X X X X X 6 6 3 3 7 7 5 4 4 5 4 Group D X X X X X X X X X X X X X X X X X X X X X X X 17 15 10 X X X X X X X X X X X X X X X X X X X 18 X X X X X 4 8 6 5 X 5 8 8 15 11 5 4 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 9 10 8 7 12 11 10 9 5 5 11 X X X X X X X X X X X X 11 12 Group E 329 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 34 39 29 33 X 3 2 2 1 3 2 2 1 1 2 4 2 3 2 3 3 4 2 2 3 4 3 2 3 6 4 1 1 2 3 2 1 3 1 2 1 1 2 1 1 1 1 1 1 1 2 1 2 1 1 1 1 2 1 3 2 1 2 3 2 2 2 2 1 1 1 1 1 1 2 1 1 2 2 2 2 1 2 2 4 26 23 16 19 14 17 12 17 27 22 32 48 44 34 37 33 A. Rambelli, B. Mulas and M. Pasqualetti Periconia sp. 1 Nigrospora sphaerica Curvularia comoriensis Cochliobolus spicifer Tubeufia helicoma Curvularia senegalensis Pithomyces maydicus Sporidesmium inflatum Bahusakala sp. 1 Spiropes dorycarpus Dictyochaeta gonytrichoides Dictyochaetopsis elegantissima Sporidesmium leptosporum Gyrothrix microsperma Berkleasmium concinnum Sporidesmium coffeicola Kionochaeta virtuosa Circinotrichum olivaceum Cochliobolus bicolor Pseudospiropes nodosus Ampullifera foliicola Gonatobotryum apiculatum Brachysporiella gayana Hemibeltrania cymbiformis Gyrothrix chimaera Dictyochaeta simplex Nectria magnusiana Triposporium elegans Sporidesmium filiferum Codinaea filamentosa Tripospermum triramiferum Dactylaria sp. 2 Sporidesmium sp. 4 Corynespora sp. 1 Gonytrichum macrocladum Sporidesmium sp. 3 Sporidesmium bambusicola Ulocladium alternariae Pseudospiropes sp. 1 Acremonium luzulae Diploöspora longispora Brachysporium nigrum Dictyochaeta fertilis Ellisiopsis occulta Pithomyces graminicola Pseudobeltrania penzigii Bipolaris papendorfii Nakataea fusispora Scolecobasidium humicola Stachybotrys atra Stachybotrys nephrospora Ramichloridium musae Tubeufia cerea Beltraniopsis tanzaniensis Kionochaeta ramifera Phialocephala dimorphospora Bahusakala olivaceonigra Pseudodictyosporium wauense Phialocephala humicola Gyrothrix citricola Pseudobeltrania guerensis Cladosporium herbarum Sporidesmium bicolor Gyrothrix podosperma Curvularia richardiae Periconia digitata Tetraploa aristata Gyrothrix ramosa Scolecobasidium longiphorum Circinotrichum poonense Memnoniella echinata Torula herbarum f. quaternella Sporidesmium pseudoseptatum Stachylidium bicolor Sporidesmium dioscoreae Anungiteopsis triseptata Wiesneriomyces javanicus Cochliobolus pallescens Dicyma ovalispora Menisporopsis theobromae Periconia cookei Corynespora cassiicola Grallomyces portoricensis Scolecobasidium constrictum Selenosporella sp. 1 Rhinocladiella selenoides Circinotrichum maculiforme Scolecobasidium tshawytschae Zygosporium echinosporum Zygosporium masonii Zygosporium gibbum Cladosporium cladosporioides Pestalotia sp. 1 Asterostomella sp. 1 Beltrania rhombica Beltraniella portoricensis Total number of species in each matrix Microfungi in tropical forest litter 330 + -+--------------+--------------+--------------+-----------+ | | | | I | | + 1+ | | K | | FCM LA | | B GED 0+ + J | | | | H | | −1 + + | | | | | | −2 + + -+--------------+--------------+--------------+------------ DIMENSION 2 2+ −2 −1 0 1 2 DIMENSION 1 A-Common and ubiquitous species (C-U) H-Percurrent conidiogenesis (PE) B-Specialized species (S) I-Sympodial conidiogenesis (SY) C-Pigmented conidia (PG) J-Septate conidia (SC) D-Hyaline conidia (HC) K-Unicellular conidia (UC) E-Presence of sterile setae (SS) L-Abundant conidial production (AP) F-Absence of sterile setae (SA) M-Low conidial production (LP) G-Phialidic conidiogenesis (PC) Fig. 1. MDS plot showing relationships between morphological and ecological characters of microfungi fruiting on incubated rain forest leaf litter. or two substrata and the nature of these substrata. As few data are available on the chemical composition of the leaf litter, the current morphologically based botanical classification was adopted which did not reveal any specific link between fungal species and plant family or genus (Table 2). Nevertheless, the finding that certain plants hosted only few fungi is noteworthy. Substrata colonised by not more than three fungal species included the following : Dichapetalum toxicarium (Dichapetalaceae) which is extremely toxic as it contains fluoroacetic acid capable of destroying the tricarboxylic acids of the respiratory cycle ; Neuropeltis prevosteoides (Convolvulaceae) which is a megaphanerophyte liana belonging to a family in which some species contain hallucinogenic substances ; Santalodes afzelii (Connaraceae), another megaphanerophyte liana belonging to a family comprising species with calcium oxalate crystals in their cell parenchyma and the seeds and bark of which are extremely poisonous, although the active compounds are not known ; Hannoa klaineana (Simaroubaceae), a mesophanerophyte belonging to a family containing species with poisonous compounds that are used for the production of insecticides; Leptoderris cyclocarpa (Leguminosae), a micro-phanerophyte liana, but the properties of this plant are unknown; Piptadeniastrum africanum (Leguminosae), another mega-phanerophyte ; Trichoscypha chevalieri (Anacardiaceae), a micro-phanerophyte with an edible fruit, but the family also contains species having allergenic resins in the resin canals ; and Diospyros kamerunensis (Ebenaceae), a nano-phanerophyte, Diospyros species being among the plants most resistant to microorganisms, with all parts containing poorly known poisonous substances that contribute to their durability (Mabberley 1997). In contrast, certain other substrata were colonised by numerous fungal species. D. sanza-minika, a mesophanerophyte that can reach a height of over 20 m, unlike the other Diospyros species, was colonised by many leaf litter saprotrophs (47 fungal species were found fruiting on incubated litter). Drypetes aylmeri (Euphorbiaceae) is a micro-phanerophyte on which 29 microfungal species fruited. In addition, the dead leaves of the following native African meso-phanerophyte trees were colonised by numerous fungal species: Uapaca guinee¨nsis (Euphorbiaceae), Xylopia aethiopica (Annonaceae ; Guinea Pepper) which is used as a medicinal plant, Sacoglottis gabonensis (Humiriaceae), and Gilbertiodendron limba (Leguminosae) (Mabberley 1997). The 184 fungal species were grouped according to ecological categories (S, C, U), revealing that 39.7 % were associated with a single substratum, and 20.1 % with two substrata. Therefore, the percentage of fungal species that may be regarded as specialised with regard to the substratum was 59.8 %. Ubiquitous species comprised 12.5 %, and common species 27.7 %. Classification of the morphological characters of the 184 species showed the following distribution: 70 % had pigmented conidia, 59 % non-septate conidia, 58 % produced few conidia, while 21 % had phialidic, 37 % percurrent, and 42% sympodial conidiogenesis. Sterile setae were found in 24% of the species. MDS was carried out on the ecological and morphological characters detected in the 184 species. In this analysis the common and ubiquitous species were grouped into a single category. The MDS plot of Fig. 1 shows two associated groups, with a statistical significance exceeding 90 % (chi square test for each paired combination of grouped characters, P<0.1). The first group contains the common and ubiquitous species that were positively correlated with hyaline conidia, abundant spore production, phialidic conidiogenesis, and the presence of sterile setae. The second group comprises the specialized species having pigmented and septate conidia and low spore production. Species with percurrent or sympodial conidiogenesis were not associated with either group (Fig. 1). Fungal species occurring on only one (73 species) or two substrata (36 species) were analysed (Table 2). Species detected on two substrata did not indicate any associations of groups of substrata. It was also evident that certain leaf litters selected high numbers of specialist fungal species: Newtonia duparquetiana 52 %, Xylopia aethiopica 30 %, Drypetes aylmeri 29%, Corynanthe pachyceras 28 %, Allanblackia floribunda 26 %, Diospyros sanza-minika 26 %, Didelotia idae 25 %, and Uapaca guinee¨nsis 17%. The ecological characters of the substrata hosting over ten fruiting species were compared. Fig. 2 a shows the percentage presence of single categories on leaf substrata ordered using cluster analysis. Three groups of substrata could be distinguished, characterised by : (1) species with numerous ubiquitous fungi fruiting Asterostomella sp. 1 Beltrania rhombica Beltraniella portoricensis Chalara alabamensis Chloridium virescens Circinotrichum maculiforme Cladosporium cladosporioides Cryptophiale kakombensis Cryptophiale udagawae Grallomyces portoricensis Gyrothrix magica Idriella fertilis Chaetosphaeria vermicularioides Periconia cookei Pestalotia sp. 1 Pseudobotrytis terrestris Rhinocladiella selenoides Scolecobasidium constrictum Scolecobasidium tshawytschae Selenosporella sp. 1 Zygosporium echinosporum Zygosporium gibbum Zygosporium masonii Idriella fertilis Chaetosphaeria vermicularioides Periconia cookei Pestalotia sp. 1 Pseudobotrytis terrestris Rhinocladiella selenoides Scolecobasidium constrictum Scolecobasidium tshawytschae Selenosporella sp. 1 Zygosporium echinosporum Zygosporium gibbum Zygosporium masonii Asterostomella sp.1 0.705±0.132 0.542±0.176 0.596±0.208 0.688±0.185 0.435±0.270 0.692±0.153 0.810±0.139 0.890±0.112 0.507±0.228 0.726±0.195 0.650±0.205 0.251±0.240 - 0.055±0.246 0.719±0.135 0.636±0.190 0.132±0.274 0.635±0.177 0.663±0.174 0.228±0.285 0.128±0.241 0.298±0.220 0.316±0.234 Beltrania rhombica Idriella fertilis Chaetosphaeria vermicularioides 0.348±0.275 0.293±0.293 0.613±0.254 0.455±0.272 0.212±0.324 0.831±0.108 0.697±0.169 0.546±0.237 0.378±0.266 0.690±0.185 0.540±0.224 0.743±0.120 0.664±0.195 0.628±0.213 0.537±0.255 0.666±0.153 0.770±0.165 0.886±0.134 0.575±0.217 0.481±0.289 0.743±0.182 0.257±0.241 0.175±0.241 0.642±0.155 0.697±0.179 0.471±0.233 0.559±0.203 0.726±0.164 0.628±0.213 0.229±0.234 0.641±0.152 0.561±0.192 0.726±0.131 0.240±0.254 - 0.034±0.305 0.249±0.270 0.729±0.137 0.396±0.242 0.789±0.127 0.412±0.216 0.547±0.186 0.772±0.116 Beltraniella portoricensis Chalara alabamensis Chloridium virescens 0.005±0.291 0.088±0.296 0.462±0.262 0.669±0.161 0.261±0.281 0.628±0.217 0.659±0.181 - 0.024±0.329 0.357±0.274 - 0.089±0.253 - 0.132±0.244 0.610±0.168 0.091±0.282 0.169±0.271 0.304±0.246 0.581±0.199 0.271±0.281 0.173±0.238 0.446±0.197 0.102±0.254 0.252±0.319 - 0.171±0.406 0.592±0.273 0.719±0.158 0.798±0.127 - 0.095±0.356 0.436±0.288 0.500±0.250 0.209±0.288 0.091±0.296 0.680±0.217 0.143±0.327 - 0.143±0.350 0.200±0.300 0.463±0.245 0.011±0.364 0.223±0.279 0.208±0.279 0.410±0.249 0.185±0.360 0.329±0.316 0.642±0.194 0.729±0.162 0.398±0.274 0.251±0.354 0.546±0.237 0.092±0.310 - 0.220±0.310 0.648±0.234 0.910±0.063 0.516±0.233 0.261±0.297 - 0.088±0.356 0.066±0.365 0.125±0.298 0.598±0.209 0.607±0.196 Periconia cookei Pestalotia sp.1 0.244±0.245 0.024±0.294 0.126±0.280 0.157±0.267 0.280±0.260 0.486±0.233 0.378±0.218 0.034±0.247 0.500±0.200 0.541±0.246 0.245±0.282 0.497±0.237 0.577±0.231 0.257±0.304 0.523±0.201 0.670±0.153 0.333±0.248 Pseudobotrytis terrestris 0.412±0.256 - 0.059±0.325 0.239±0.297 0.200±0.324 - 0.014±0.293 0.429±0.239 0.008±0.307 Circinotrichum maculiforme - 0.026±0.336 - 0.121±0.414 - 0.432±0.446 0.324±0.310 0.360±0.334 0.471±0.277 0.424±0.265 0.322±0.287 0.346±0.316 0.324±0.310 0.278±0.318 0.692±0.165 0.835±0.108 0.420±0.290 0.745±0.161 0.498±0.264 0.608±0.207 Rhinocladiella selenoides 0.265±0.279 0.186±0.302 0.834±0.103 0.513±0.211 0.335±0.248 0.556±0.199 Cladosporium cladosporioides 0.782±0.208 0.735±0.248 0.624±0.246 0.416±0.342 0.760±0.207 0.514±0.230 0.339±0.247 0.880±0.071 0.425±0.287 - 0.086±0.291 0.704±0.202 0.446±0.272 0.556±0.281 0.366±0.239 0.739±0.142 0.481±0.241 Cryptophiale kakombensis 0.990±0.012 0.398±0.274 0.481±0.275 0.546±0.237 0.277±0.283 - 0.024±0.311 0.832±0.165 0.558±0.221 0.150±0.328 0.435±0.254 0.351±0.283 0.076±0.375 0.455±0.241 0.298±0.209 0.316±0.277 Cryptophiale udagawae 0.324±0.320 0.370±0.334 0.241±0.354 - 0.212±0.344 - 0.548±0.286 0.793±0.200 0.514±0.248 0.034±0.366 0.189±0.329 0.278±0.318 0.121±0.414 0.091±0.320 0.489±0.254 0.065±0.336 Scolecobasidium Scolecobasidium Selenosporella constrictum tshawytschae sp.1 0.553±0.205 0.696±0.164 0.392±0.231 0.771±0.129 0.756±0.127 0.649±0.185 0.724±0.146 0.606±0.190 0.560±0.199 0.455±0.241 0.725±0.167 0.718±0.155 Grallomyces portoricensis 0.391±0.299 0.260±0.318 0.775±0.126 0.345±0.254 0.862±0.138 0.290±0.291 0.673±0.179 0.790±0.119 0.412±0.255 0.782±0.129 0.686±0.163 0.680±0.163 0.713±0.150 Zygosporium echinosporum 0.700±0.137 0.860±0.081 Gyrothrix magica 0.802±0.130 0.104±0.339 0.070±0.340 0.525±0.298 0.391±0.299 0.104±0.377 0.625±0.208 - 0.200±0.402 - 0.059±0.421 - 0.042±0.340 0.222±0.313 0.356±0.292 A. Rambelli, B. Mulas and M. Pasqualetti Table 3. Yule coefficients of association (Q) and asymptotic standard errors calculated for fungal species present on over ten substrata; the underlined values were significant (P<0.01) in chi-square tests. Zygosporium gibbum 0.770±0.210 331 Microfungi in tropical forest litter 332 (a) 100% S C 80% U 60% 40% 20% 0% U S (b) 100% HC PG 80% 60% 40% 20% 0% (c) 100% 80% 60% 40% 20% 0% Fig. 2. (Cont.) UC SC A. Rambelli, B. Mulas and M. Pasqualetti 333 (d) 100% LP AP 80% 60% 40% 20% 0% (e) 100% SY PE PC 80% 60% 40% 20% 0% ( f ) 100% SA SS 80% 60% 40% 20% 0% Fig. 2. (a) Percentages of single (S), common (C) and ubiquitous (U) colonizers on substrata hosting over ten fungal species ; the substrata are ordered by cluster analysis. Sporulation characters are coded as follows : (b) percentage of species with hyaline (HC) and pigmented (PG) conidia on substrata hosting over ten fungal species ; (c) percentage of species with unicellular (UC) and septate (SC) conidia on substrata hosting over ten fungal species ; (d ) percentage of species with low (LP) and abundant conidial production (AP) on substrata hosting over ten fungal species ; (e) percentage of species with phialidic (PC), percurrent (PE) and sympodial (SY) conidiogenesis on substrata hosting over ten fungal species ; and ( f ) percentage of species with (SS) and without sterile setae (SA) on substrata hosting over ten fungal species. Microfungi in tropical forest litter and few unique or common fungal species (from Lovoa trichilioides – au, to Calpocalyx brevibracteatus – c) ; (2) species with many common and ubiquitous fungi fruiting (from Memecylon lateriflorum – r, to Landolphia hirsuta – bs) ; and (3) species with a significant number of specialist species fruiting (from Xylopia aethiopica – ac, to Newtonia duparquetiana – bt). Fungal species that occurred only once were more numerous than common and ubiquitous species in Newtonia duparquetiana (bt). Fungal species fruiting on more than ten substrata were analysed (Q association index) in order to detect significant association between them (Table 3). Regular associations were recorded between Cryptophiale udagawae and C. kakombensis (0.99), and between Chaetosphaeria vermicularioides and Pseudobotrytis terrestris (0.91), that were practically always associated with the same substrata. Equally high and significant associations (Q>0.8) were found between the abovementioned two species of Cryptophiale and Asterostomella sp. 1, and also between Beltrania rhombica and C. udagawae, Circinotrichum maculiforme and Scolecobasidium tshawytschae, Cladosporium cladosporioides and Pestalotia sp. 1, C. kakombensis and Pestalotia sp. 1, Grallomyces portoricensis and Pestalotia sp. 1, Gyrothrix magica and Idriella fertilis, I. fertilis and Scolecobasidium constrictum, Rhinocladiella selenoides and Selenosporella sp. 1, and Zygosporium echinosporum and Z. masonii. Moreover, Z. echinosporum, Z. masonii and Z. gibbum showed a significant correlation index of over 0.7. Morphological characters of certain species occurring on substrata hosting over ten colonizers were analysed. In Fig. 2 b conidial pigmentation was taken as the criterion, and the percentage of species with pigmented conidia was calculated for each leaf type was compared with the mean percentage value of all fungal species. In some substrata, the distribution diverged greatly from the mean value (70 % of pigmented conidia). Over 80% of the fungi fruiting on litter of Xylopia aethiopica, Allanblackia floribunda, and Symphonia globulifera had pigmented spores ; in particular, S. globulifera did not host any species with hyaline conidia. In contrast, less than 60% of the fruiting fungi had pigmented conidia on Calpocalyx brevibracteatus, Chrysophyllum taiense, Tetracera potatoria, Memecylon lateriflorum, Anthonotha fragrans, Sacoglottis gabonensis, Lophira alata, Diospyros mannii, Memecylon donianum, and Decorsella paradoxa (Fig. 2b). Furthermore, in some substrata the distribution of fungi with septate conidia deviated from the mean distribution (41 %). In particular, Newtonia duparquetiana hosted over 60 % of fruiting species with septate conidia, whereas Calpocalyx brevibracteatus, Tetracera potatoria, Lophira alata, Diospyros mannii, Guarea thompsonii, and Landolphia hirsuta had over 80% of fruiting fungal species with one celled conidia (Fig. 2 c). Finally, abundant conidial 334 production (mean value 42%) exceeded 60% in Coula edulis, Memecylon lateriflorum, Lophira alata, Newtonia aubrevillei, and Guarea thompsonii, while it was below 30% in Lovoa trichilioides and Newtonia duparquetiana (Fig. 2 d ). Fig. 2e shows the percentages of the various types of conidiogenous cells. Phialidic conidiogenous cells occurred in about 20% the 184 species; in litter of many species hosting more than ten fruiting species, this number deviated greatly from this average. In particular, litter of Manniophyton fulvum, Calpocalyx brevibracteatus, Chrysophyllum taiense, Dialium aubrevillei, Lophira alata, Lovoa trichilioides, Newtonia aubrevillei, Diospyros mannii, and Guarea thompsonii hosted over 40 % of phialidic-fruiting species, while Symphonia globulifera and Ficus sagittifolia had less than 10%. Fungal species with sympodial conidiogenesis (mean values 42 %) often exceeded 50 %, such as in Tetracera potatoria, Diospyros cooperi, Corynanthe pachyceras, Memecylon lateriflorum, Xylopia aethiopica, Symphonia globulifera, Beilschmiedia mannii, and Ficus sagittifolia, while it was below 30% in Manniophyton fulvum and Newtonia duparquetiana. In particular, N. aubrevillei and Ficus sagittifolia did not host any fruiting fungi with percurrent conidiogenesis, and over 90 % of the species had sympodial conidiogenesis in the latter (Fig. 2 e). Plant species hosting fewer than 20 % fruiting fungi with percurrent conidiogenesis (average 37%) included : Manniophyton fulvum, Calpocalyx brevibracteatus, Coula edulis, Chrysophyllum taiense, Diospyros sanza-minika, Tetracera potatoria, Diospyros cooperi, Corynanthe pachyceras, Lophira alata, Lovoa trichilioides, Diospyros mannii, and Beilschmiedia mannii. In contrast, N. duparquetiana had more than 60 % of the fruiting species with percurrent conidiogenesis (Fig. 2e). Finally, some plant substrata were found where the presence of sterile setae in the fruiting structures exceeded the mean value (24 %). Presence of setae exceeded 40% of the fruiting species in Calpocalyx brevibracteatus, Chrysophyllum taiense, Tetracera potatoria, Anthonotha fragrans, Lophira alata, Memecylon donianum, Ficus sagittifolia, and Landolphia hirsuta (Fig. 2 f ). DISCUSSION The study focuses on relationships between plant host and associated saprotrophic fungal communities, and builds on other comparative investigations on microfungi in the tropical environments of Tai National Park (Rambelli et al. 1983, 1984, 1991). Microfungal species that fruited on incubated leaf litter samples were identified and characterised, and the characteristics of the fungal communities were then correlated with the host plants. The detection on specialized plant-fungus species relationships is noteworthy as it confirms the existence in tropical forest ecosystems of the previously observed saprotrophic specialisation (Lodge & Cantrell A. Rambelli, B. Mulas and M. Pasqualetti 1995). In totally different environmental conditions, fungal communities supporting major environmental stress were observed in the Mediterranean maquis (Mulas et al. 1995, Pasqualetti et al. 1999). These preliminary observations show that saprotrophic specialisation is not linked to particular environments and substrata, but is a natural phenomenon occurring to different degrees in all environments. It can be assumed that in environments where conditions are optimal for microfungal development (humidity and temperature), such as in tropical forests, saprotrophic specialisation is mainly related to nutritional factors and the secondary chemistry of the substrata. The data presented were analysed for the distribution of 184 saprotrophic fungi on litter of 71 plant species. This enabled us to observe significant correlations between certain morphological and ecological parameters of hosts and fungal colonizers. The data obtained revealed that ubiquitous-common and specialist fungi have quite distinct characteristics, except for percurrent and sympodial conidiogenesis which occurs in both groups (Fig. 1). Specialist species show limited production of often multicellular, resistant, pigmented and scarcely vulnerable conidia. This may imply that these species are greatly involved in vegetative propagation and are the main driving force behind the degradation of the substrata. In fact, it seems reasonable to suggest that if there is a high degree of fungal sepcialisation related to the substrata, the microfungi involved may have adopted vital strategies whereby energy is mostly consumed for vegetative growth and not for reproduction. These species need not compete for the substratum and their highly resistant conidia permit colonisation of adjacent similar substrata, not in competition with other fungi but as selected by the substratum. The common or ubiquitous species showed a different behaviour with divergent morphological and ecological characters. 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