Diversity offilamentous fungiin leaflitter and aeriallitter in semideciduous forest,Bahia,Brazil

Marcos Fabio Oliveira Marques?Edemir Barbosa dos Santos?Lu?′s Fernando Pascholati Gusma?o

The fungihave wide distribution in ecosystems and can be found colonizing various substrates,where they act as efficient decomposers,participating in cycling of nutrients.The present study aimed to assess the diversity, richness and composition of filamentous fungi in leaf litter and aerial litter in a semi-deciduous forest in the Chapada Diamantina,Bahia,Brazil.Samples of leaf litter and aerial litter were collected monthly from October/2009 to September/2010 in eight installments in the studied area. Those samples were washed,placed in moistchambers and incubated.47 taxa were identified,37 in leaf litter and 35 in aerial litter,with 25 species common to both.A similarity of 69%according to Sorensen index.The similarity was considered low when the sample points were compared to the same litter.Most fungi showed sporadic intervals.

Plant debris·Species richness·Tropical microfungi

Introduction

The dry areas of the world harbor a unique biological diversity on the planet.Although not characterized by high levels of diversity among the species,these areas have high levels of endemism and include a unique ecosystem. Dwelling organisms associated with these ecosystems are deprived of nutrients and often face environmentalstresses due to low rainfall and periodic droughts(Montenegro 2001).

The decomposition of the litter layer is important for ecosystems due to the cycling of organic and inorganic nutrients through the action of micro-organisms(Couteaux et al.1995;Saura-Mas et al.2012).Among them,filamentous fungi contribute the most to decomposition because hyphae have the ability to break the surface of the plant and penetrate into the mesophyll(Bray and Gorham 1964).Leaf litter makes up 60–80%of the litter in differentforests worldwide(Jensen 1974).On the other hand, aerial litter composed of dead leaves suspended in the vegetation or deposited in trunks and/or hollow trees (Gradwohl and Greenberg 1982)comprises a small portion of small vegetation.

In tropicaldry forests,production and leaf litter decay is influenced by seasonality and the composition of plant species(Anderson and Swift 1983;Fujimaki et al.2008). Both types of litter present inconsistent production throughout the year as seen in semi-deciduous forests,and the litter,according to Mercado-Sierra et al.(1987),is a somewhat varied selective substrate that is widely colonized by fungi.

This study aimed to assess the diversity,richness and composition of filamentous fungi in leaf litter and aerial litter in a semi-deciduous forest in the Chapada Diamantina,Bahia,Brazil.

Materials and methods

Study site

The Parque Estadual das Sete Passagens(PESP)is located in the northern portion of the Chapada Diamantina(lat 40°32′23′N,long 11°23′26′E)at Miguel Calmon,Bahia, Brazil.This area of the PESP is rich in water resources, fauna and flora(Bastos and Yano 2006,2008,2009; Mace?do and Drummond 2010;Xavier and Napolli 2011). The study area has the vegetation of semi-deciduous forest and vegetation rupestrian field.The average temperature of the coldestmonth(July)is lower than 18°C and the hottest month(January)is lower than 22°C(Mace?do and Drummond 2010).There is less than 800 mm of rainfallper year.

Survey design and assessment of Microfungi diversity

From October 2009 to September 2010,samplings were taken monthly at eight different points(10×10 m equidistant at an interval of at least 10 m),(Table 1).

On each sampling date,five leaves of leaf litter and five leaves of aerial litter were collected randomly from each delimitated point.For the collection of the ground litter,a 900 cm2PVC square was thrown out randomly to selectthe leaves from the surface.The aerial litter was selected from whatwas found in the hollows of the trees in the area of study.The leaves were collected independentof the size, the plant species or the state of decomposition,thus respecting their deposition in the area.The samples were washed,as described in Marques etal.(2008),and saved in moist chambers at room temperature for 30 days.The reproductive structures of fungi were collected with the aid of a fine-tipped needle and placed in a permanentmounting medium with PVL resin(polyvinyl alcohol+lactophenol) constituting permanent slides.The sample specimens were deposited in the Herbarium atthe Universidade Estadualde Feira de Santana(HUEFS).

Table 1 Characteristics of the sample parts in the seasonal semideciduous forest in the Parque Estadual das Sete Passagens,Miguel Calmon,BA

Definitions and statistical analysis

Taxa were registered as either present or absent for each substrate(leaf litter and aerial litter).The periodicity of occurrence of each species of fungi in each substrate was calculated based on the following formula(Muthukrishnan et al.2012),modified:Periodicity of occurrence (PO)=number of samples containing the species analyzed/occurrence of all taxa in the substrate×100,being classified as‘Most common—MC(76–100%),‘common’—C(51–75%),‘occasional’—O(26–50%)and‘sporadic’—S(1–25%).

The Sorensen similarity index(S)was used to compare the similarity of species from different litters:S=2c/ (a+b),where a is the totalnumber of species of leaf litter, b is the total number of species of aerial litter and c is the number of species that were common to both litters.Similarity is expressed with values between 0(dissimilar)and 1(completely similar)or expressed by percentage(Mueller-Dombois 1981).

Results

We identified 47 fungi taxa,33 genera of which were filamentous fungi.Among the substrates,37 taxa were associated with leaf litter and 35 with aerial litter.The percentage of occurrence and the composition of the fungal community in each of the eight sampling points was different for each of the samples(Appendix 1).The most common species in the ground leaf litter were Atrosetaphiale flagelliformis(20%)at point 1,Beltrania rhombica and Chloridium sp.(22.2%)at point 2,Cryptophiale kakombensis at point 3(25%),6(26.6%)and 7(42.8%) and Cryptophialoidea fasciculata(18.1%)at 5.In the aerial litter,the species B.rhombica and Beltraniella portoricensis showed an occurrence of 33.3%at point 1. Circinotrichum olivaceum and A.flagelliformis had the highest occurrence,each with 37.5%at 2 and 7,respectively.At points 3,8(25%)and 4(30.7%)there was the highest occurrence of the specie Beltraniella portoricensis.For point 6,A.flagelliformis,B.portoricensis and Kionochaeta ramifera showed the highest occurrence at 16.6%(Appendix 1).

The following species were recorded as exclusively associated with aerial litter.Endophragmiella rigidiuscula, Hemibeltrania decorosa,Polydesmus elegans,Sporidesmium inflatum,Stachybotrys parvispora,Vermiculariopsiella cubensis,Zygosporium echinosporum and Zygosporium masonii.The richness of species differed among study points,the richness and occurrence being highestat point6 for the ground leaf litter and at point 3 for aerial litter (Tables 2,3).

The highest richness of species was found associated with leaf litter(37)when compared to aerial litter(35), being 25 taxa common to both substrates.The comparison between the leaf litter and aerial litter revealed a high similarity of 0.69(Fig.1).

There was a dissimilarity between sample points and recorded values were low.The highest value(46.1%)wasbetween points 5 and 7 for the leaf litter,and 57.1% between points 2 and 4 for the aerial litter(Tables 2,3).

Table 2 Index of similarity among the eight sampling points for filamentous fungi from ground leaf litter

Table 3 Index of similarity among the eight sampling points for aerial leaf litter

Fig.1 Richness and similarity index between species found in leaf litter and aerial litter in PESP,Miguel Calmon,BA

Discussion

The richness of filamentous fungi species from leaf litter and aerial litter reflects the possibility of existence in substrates that are susceptible to their colonization. According to Harley(1971)fungal colonization of these substrates is facilitated because they synthesize a series of enzymes that aid in the degradation of organic and inorganic compounds,facilitating the reintroduction of nutrients in ecosystems.Thus,it was demonstrated by the richness of the substrates supplied by the plants in the area as well as by the different stages of degradation which allowed for identification of the fungi that participate in various states of the decomposition process.

The richness of fungi associated with the aerial litter was considered high,justas itwas recorded in studies with other groups of organisms.Higher numbers of Myxomycetes species were found associated with aerial litter than with barks and leaf litter.These differences were associated with the physical characteristics of these substrates (Schnittler and Stephenson 2000;Black et al.2004;Macabago et al.2010).Such characteristics are observed in this study by the presence of trichomes and the leathery texture of leaves.

For all purposes,the climatic characteristics and diversity of litter in the area investigated provided conditions for saprobe mycota actuation.The study showed that few fungi species are exclusive to any one type of litter,mainly when working with a mixed substrate from various seasonal semi-deciduous forest plants which in suspended conditions or deposited on the ground,the degradation process by fungi occurs.Meguro et al.(1980) found that several factors influence the decomposition process of leaves,such as the chemical structure and the physical characteristics of each plant species.Parungao et al.(2002)attributed the low fungal diversity found associated with 13 different types of plants to the structure of the leaves,which were thin and brittle.

The composition of the taxa found is widely reported in literature,similar to the decomposers of plant material in other areas,as expected.The periodicity of occurrence revealed the predominance of sporadic species,with low occurrence of occasional and common species in both substrates.The sporadic occurrence suggests that many of these fungi are not frequent in the area or that are found during the periods of the year in the resistance stage.These results are similar to others performed that demonstrate the predominance of sporadic species (Heredia 1993;Muthukrishnan et al.2012;Magalha?es et al.2011).

Many studies have been done to investigate filamentous fungi in specific substrates and have shown a greater or lesser number of species.In the study done with mixed litter,it verified similar richness standards,however there were differences in the composition of species among the litters,but they presented a large number of species that were common among them.Studies with specific substrates,like that performed by Polishook et al.(1996) with species of Guarea guidonia(L.)Sleumer(Meliaceae)and Manilkara bidentata(ADC)Chev.(Sapotaceae) in a forest in Puerto Rico.From direct observation,they identified 24 species of filamentous fungi,being 11 in G. guidonia and 18 in M.bidentata and six common forms, and Parungao et al.(2002)recorded 39 filamentous fungi in 13 different vegetables in Queensland,Australia.These studies demonstrated the importance of the substrate in the colonization of filamentous fungi,which is a limiting factor for fungal growth.The differences in collection points in this study may be associated with the origin of the investigated materials,which came from a range of plants present in the area studied once the mixed plant litter was collected at each sample point.It is important to note that the above studies were carried out with different techniques to access the filamentous fungi.

The occurrence of filamentous fungi,commonly recorded in the litter,was found in this study to be exclusively colonizing the aerial litter(E.rigidiuscula,H. decorosa,P.elegans,S.inflatum,S.parvispora,V.cubensis,Z.echinosporum and Z.masonii),can be attributed to a number of factors,such as explained by Heredia-Abarca(1994),that leaves at any stage of their life cycle are a substrate suitable for the development of various types of filamentous fungi,because when the leaves die, some fungal species disappear and are replaced by others that survive the new nutritional and environmental conditions that prevail in the substrate.Thus,it explains the presence of fungi in a variety of aerial litter that was not registered in the leaf litter,as well as the presence of some genera of parasites,such as:Curvularia and Stachybotrys,and therefore the fungi associated with the leaves comprise a well-defined ecological group presented by saprobes and parasite species(Heredia and Estebanez-Reyes 1999).However,Curvularia and Stachybotrys are a common species that occur in leaf litter and they are not exclusively parasitic(Gusma?o et al.2005;Santa-Izabel et al.2010).

The comparative study of leaf litter and aerial litter showed higher richness values than just the leaf litter as well as differences in composition of species among the sample points.This spatial diversity is associated with the floristic heterogeneity of the sample points that provides suitable substrates to be colonized by filamentous fungi saprobes.The differences observed may be related to environmental conditions,degree of decomposition and variation in the incidence and richness of litters.Bills and Polishook(1994)associated the high diversity of fungi in tropical forests partly to the floristic variability and to the other organisms that compose it.On the other hand,Kirby et al.(1990)reported that the differences in the composition of the litter and in different substrates interferes in the sporulation of some fungal species.Despite all of the studies and modern techniques,the ecology of filamentous fungi,particularly in the leaf litter of rainforest trees,was considered a difficulttask by Paulus etal.(2006)due to the large number of species and the limitations of currently available quick and reliable methods for the detection of fungal diversity.

The community of filamentous fungi from leaf litter and aerial litter showed a high similarity since substrates were from the same area of investigation,just as that coming from a range of plant species,thus both tend to have the composition of the closer fungal community.It was observed that there are differences even between communities of microfungi in litter fromthe same plant species that occur in different areas. Therefore,comparing microfungi isolated from leaves G.guidonia(L.)Sleumer(Meliaceae)and M.bidentata (A.D.C)Chev.(Sapotaceae)in Puerto Rico,through direct observation of moist chambers recorded among samples of the same species in different areas 44%for M.bidentata and 50%to G.guidonia,but comparing the two species in areas 1 and 2 we had 28 and 25% of similarity,respectively(Polishook et al.1996).It was also noted that the communities that occur in the species from the same plant genre are distinct and that this similarity can vary quite a bit.Thus,Wang et al. (2008),having studied five species of Ficus in northern Thailand found a variation between 28 and 45%of similarity among the substrates investigated.On the other hand,Heredia(1993)studied species of Quercus and Liquidambar in moist forests in Mexico that showed significantly similar composition among combinations of species:Quercus germana Cham.and Schlrcht versus Quercus sartorii Liemb.with 86%;Q. germanic and Liquidambar styraciflua L.72%and L. styraciflua and Q.sartorii with 73%.This was different from what was found in this study for mixed litter. Marques et al.(2008)reported a low similarity(25%) of the fungal community between the Atlantic Forest in the Serra da Jiboia,Bahia,which was caused by the different plant species and environmental characteristics of the areas investigated.Works that analyzed specific species of plants with mixed substrates revealed the variation in similarity,showing that a number of factors can influence fungal colonization and determine the composition of the community,greater similarity not occurring naturally between samples of the same plant species from different areas.

Thus,it was observed in this study that each sampled substrate exhibited distinct fungal composition at the points investigated.So,floristically distinct areas contribute to diverse substrates,which often limit or favor fungal colonization.Thus,the continuation of this study will allow for a better understanding of the inner working and dynamics of fungal communities in these forest areas.

AcknowledgmentsThe authors thank the Post-graduation in Botany Program—PPGBot/UEFS and PPBIO/CNPq(Biodiversity Research Program in Semiarid Regions,proc.558317/2009-0)and CNPq for the Grant to the LFP Gusma?o(proc.305413/2011-2).

Appendix

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3 February 2014/Accepted:10 June 2014/Published online:27 January 2015

?Northeast Forestry University and Springer-Verlag Berlin Heidelberg 2015

Project funding:This research was supported by the Post-graduation in Botany Program—PPGBot/UEFS and PPBIO/CNPq(Biodiversity Research Program in Semiarid Regions,proc.558317/2009-0)and CNPq for the Grant to the LFP Gusma?o(proc.305413/2011-2).

The online version is available at http://www.springerlink.com

Corresponding editor:Zhu Hong

M.F.O.Marques(?)·E.B.dos Santos

Laborato′rio de Biologia Molecular de Fungos,Universidade do Estado da Bahia,Campus VII,Br 407,Km 127,Rod.Lomanto Ju′nior,Senhor do Bonfim,BA 44230-000,Brazil e-mail:mfmarques@uneb.br

L.F.P.Gusma?o

Laborato′rio de Micologia(LAMIC),Universidade Estadual de Feira de Santana,Caixa Postal 252,Feira de Santana, BA 44036-900,Brazil