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1 Department of Genetics, Forestry and Agricultural Biotechnology Institute
(FABI), University of Pretoria, Pretoria 0002, South Africa
2 Private Bag X402, 1350 Skukuza, Kruger National Park, South
Africa
*
Correspondence: Wolfgang Maier,
wolfgang.maier{at}fabi.up.ac.za
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Abstract |
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 TOP Abstract INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Keywords Basidiomycota / Coniodictyum / Cryptobasidiaceae / epidemic fungal disease / Exobasidiales / Kruger National Park / South Africa / Ustilaginomycetes / Zizyphus mucronata
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INTRODUCTION |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Buffalo Thorn (Zizyphus mucronata) is a common tree species in the Southern African Savanna and Nama Karoo biome (biome definition according to Rutherford (2003). This savanna habitat distribution is also mirrored by its overall distribution in Africa (Fig. 1). In these areas, it is found on many different soil types, but it is especially abundant on brackish flats, along rivers on alluvial soils, and it also shows a special preference for termite mounds (van Wyk 1984, Coates Palgrave 2002). Due to its abundance, Z. mucronata is an important food source for a great variety of animals both browsing (e.g. elephant, giraffe, black rhino, kudu) and fruit-eating (e.g. warthog, monkeys, birds). Furthermore, Z. mucronata plays a central role in the nutrition of a number of insects, being for example a crucial food source for the larval caterpillars of the Atlas Moths Epiphora mythimnia and E. bauhiniae vera (Pinhey 1972).
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In late March 2004, large numbers of spectacular snow-white powdery balls were observed mainly on the branches and fruits of Z. mucronata trees in the southern part of Greater KNP. In this study, we consider the identity of the fungus causing the epidemic gall disease on Z. mucronata in the KNP. The fungus is described in detail and its phylogenetic placement is determined based on DNA sequence comparisons. The associated disease is discussed and illustrated comprehensively, for the first time providing photographic records, and its relative importance is considered.
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MATERIALS AND METHODS |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Observations for this study were made in the southern part of Greater KNP. To understand the overall distribution of the disease, we monitored the fungal galls that could be seen from the park tracks. Park rangers also monitored the distribution of the fungus with the help of GPS-devices during their routine control tours in June and July 2004. Thus, the overall distribution of the disease in the national park could be extrapolated although large parts are not easily accessible. In 2005 the same regions of the park were surveyed again for the disease. To quantify the disease prevalence at representative sites in the park, a census was conducted in Manyeleti (compare Fig. 3) in mid May 2004. Two of the census plots were approximately 2 ha in size, representing dense bushveld, a dense form of savanna, and the third was situated in a depression next to a dam. Each Z. mucronata tree in these plots was scrutinized for the conspicuous fungal galls. The presence or absence of the disease on trees was monitored at these sites.
Morphological comparisons and isolations
For light microscopy, free-hand sections of the fungal hymenium situated at
the surface of the galls and detached spores were mounted either in water,
clear lactophenol, cotton-blue lactic acid or Hoyer's fluid
(Cunningham 1972) and examined
using a Zeiss Axiovision microscope with phase contrast and interference
optics. Drawings were made of both spores and the most frequent disease
symptoms on branches and fruits.
Spores were also examined using scanning electron microscopy (SEM). For this purpose spores were fixed on double-sided adhesive tape on a stub and sputter-coated with gold with an E5200S sputter coater (Polaron, Watford, England). The samples were subsequently examined with a JSM-840 scanning electron microscope (JEOL, Tokyo, Japan).
To obtain cultures, spores were thinly dusted onto the surface of malt-yeast-peptone agar (Van der Walt & Yarrow 1984) in Petri dishes. The Petri dishes were kept at room temperature or in incubators at 25° C: Cultures of the fungus have been deposited in the culture collections of the Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria (CMW 23046, CMW 23047).
All collections listed in Doidge (1950) under Coniodictyum evansii that had been deposited in the National Mycological Herbarium in Pretoria (PREM) were examined. These include herbarium accession numbers PREM 92, 1006, 1214, 2537, 5648, 8789, 10090, 11240, 11812, 15019, 20611, 30667. It was not possible to obtain the collection Rh 146, the only report on Z. jujuba, which had been deposited in the then Mycological Herbarium of the Department of Agriculture, Southern Rhodesia, which is now the National Herbarium of Zimbabwe. Representatives of our collections are deposited at PREM (PREM 59000-WM3450, PREM 59001-WM3488).
DNA sequence comparisons and phylogeny
In order to confirm the identity of the fungus as determined based on
morphological characteristics, DNA sequence comparisons were made and
phylogenetic trees were inferred. DNA was isolated directly from the spores of
infected branches and fruits as well as from cultures using Qiagen Plant Mini
Kit (Qiagen, Hilden, Germany) following the manufacturer's protocols. For
mechanical cell disruption, spores were crushed between microscope slides, or
in the case of culture material, by using a micro pestle in an Eppendorf cup,
which was cooled with liquid nitrogen. PCR and direct sequencing of both
strands of the 5' end of the large subunit of the ribosomal gene cluster was
performed using the primer pair LR 0R
(Moncalvo et al.
1995) and LR 6 (Vilgalys &
Hester 1990). PCR and cycle sequencing settings were the same as
those described by Ritz et al.
(2005). DNA sequencing was
done on an ABI PRISM 3100TM sequencer (Perkin-Elmer, Warrington, U.K.).
Contigs of the double-stranded nucleotide sequences were obtained and edited
with the help of Sequencher 4.5 (Gene Codes Corporation, Ann Arbor, Michigan).
All available sequences of Cryptobasidiaceae were obtained from
GenBank and accompanied by sequences from Graphiolaceae and
Brachybasidiaceae. Representatives of the latter two families were
used to root the phylogenetic trees. The GenBank accession numbers follow the
species names on the phylogenetic tree.
From the above sequences an alignment was produced with MAFFT 5.66 (Katoh et al. 2005) using the iterative refinement method with the following settings: the Needleman-Wunsch algorithm active, 2 tree rebuilding steps, 1000 iterations and default values for gap opening and gap extension penalties (NW-NS-i: –nofft –retree 2 –maxiterate 1000 [–bl 62] –op 1.530000 –ep 0.123000). Phylogenetic trees from this alignment were derived by Bio Neighbour Joining (BioNJ (Gascuel 1997) with the help of PAUP 4.0b10 (Swofford 2001) and by Bayesian inference using Metropolis Coupled Monte Carlo Markov Chains (MC3) and MrBayes 3.1.1 (Huelsenbeck & Ronquist 2001, Ronquist & Huelsenbeck 2003), respectively. Branch support for neighbour joining was determined by 5000 bootstrap replicates. For BioNJ the best fitting model (TIMG) of DNA substitution was determined with the Akaike Information Criterion (Akaike 1974) implemented in Modeltest 3.7 (Posada & Crandall 1998) and then used to obtain both the phylogram and the bootstrap consensus tree. In the case of MC3 the GTR+I+G model (Tavaré 1986, Yang 1993, 1994), as the most complex model, was chosen according to the simulation study results of Huelsenbeck & Rannala (2004) and default values for the prior settings. Three runs of MC3 with 1.000.000 generations were performed, and every 100th generation was sampled resulting in 10001 trees. The first 1001 trees were discarded and the remaining 9000 trees were used, well after the chains had converged to stationarity, to estimate the posterior probability distribution. One MC3 analysis was run over 6.000.000 generations to marginalize the chance that we might have missed a higher plateau of stationarity. In this case the majority rule consensus tree was constructed from 50.000 trees and 10.001 trees were discarded as "burn-in". The sequences derived in this study have been deposited in GenBank with the following accession numbers (DQ334805 [GenBank] , DQ334806 [GenBank] ), the alignment is lodged in TreeBase (study accession number=S1474, matrix accession number=M2652).
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RESULTS |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Using SEM, it was possible to observe for the first time that the surface of the presumed basidiospores is covered more or less densely with small warts (Fig. 6) that cannot be seen with the light microscope. The spores germinated on artificial media, at first producing conidia and yeast cells (for detailed microscopical descriptions of these compare Malençon (1953). Cultures grew very slowly (ca. 1 mm diam after 5 – 7 d). After about 3 – 5 wk, the single-spore cultures had transformed into a solid slightly salmon-coloured compact hyphal mass displaying a brain-like surface structure.
The collections of C. chevalieri deposited in PREM had been collected in the following provinces of South Africa: Limpopo, Mpumalanga, KwaZulu-Natal and Gauteng. They include the type collection of Hyalodema evansii (PREM 92). Nine of the twelve specimens had initially been labelled as H. evansii P. Magnus before being transferred to C. chevalieri Har. & Pat. The remaining three specimens (PREM 92, 2537, 5648) had been labelled as Coniodictyum evansii P. Magn. This is also the name that was used in Doidge's compendium on the Southern African fungi (Doidge 1950). However, this is not a valid name as discussed below. Doidge (1950) also lists a collection from Zimbabwe that was reported from Z. jujuba.
Distribution and prevalence of the disease in 2004 and 2005
The disease was first discovered in the southern parts of the park in late
March 2004, in the area of the camps Skukuza, Orpen, and Lower Sabie. The peak
of the disease was reached in May/June when it was detected to have spread
over a distance of about 200 km on the north-south axis and the entire
east-west extension of the park (Fig.
3). Infections remained clearly visible on trees until August. The
census taken at the two plots representing dense bushveld revealed that all 43
and 53 trees, respectively, in these plots were diseased. At the third plot
next to the dam, all 38 trees counted were diseased. This amounted to a
disease prevalence of 100 % in the region. The majority of trees at all three
plots were heavily infected, however medium-infected trees and trees with
hardly any infection could also be found.
During the first half of 2005, rangers did not notice signs of the disease in the park. Likewise, symptoms were not observed in roadside surveys of Z. mucronata trees undertaken during April and June 2005. The three reference plots were, therefore, closely investigated on foot. None of the trees in the two bushveld reference plots that had displayed 100 % disease incidence in the previous year showed fresh infections. However, viable spores that could be germinated on MYP agar were obtained from two galls from previous year infections. All of the trees were alive but many of the heavily infected branches, easily detectable by the presence of old galls, had died. There was also practically no fruit production in 2005, while the trees had produced abundant fruit at the same time in the previous year. The reference trees close to the dam had recovered more effectively than the trees at the two other census sites. They also displayed abundant fruit production, and small numbers of weak infections could be found on the fruits of six trees.
DNA sequence comparisons and phylogeny
Sequences were obtained from spores of different host organs (branches,
fruits) of different trees from different sample sites as well as from
cultures grown from spores. The sequences spanned the D1 – D3 region of
the nuc LSU rDNA with a length of about 1000 bp. All eight sequences obtained
were identical. They were also identical to the only available sequence of
C. chevalierin in GenBank that had been deposited for a study of the
Exobasidiales (Begerow et
al. 2002). This sequence was derived from a culture obtained
from material collected by Johannes van der Walt in 1990 around Skukuza camp,
also in KNP.
The final alignment used for the phylogenetic analyses was restricted to the D1/D2 region, due to the length of the sequences deposited in Genbank, and comprised 508 base pairs. Tree topologies obtained by four different runs of MC3 were identical. Tree topologies obtained by MC3 versus BioNJ were almost identical. The only difference was that the four Laurobasidium specimens were resolved as a monophyletic group in MC3, whereas in BioNJ Laurobasidium lauri was the sister group to the three samples of Laurobasidium hachijoense together with the Clinoconidium spp. as a whole. The posterior probabilities and bootstrap values were similar (compare Fig. 7). The most important support values for this study are those for Cryptobasidiaceae (1.00 posterior probability / 99 % bootstrap) and those for the split between Coniodictyum (1.0/100) and the rest of the Cryptobasidiaceae (1.00/100).
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DISCUSSION |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Coniodictyum chevalieri was first described in 1909 from Chad on Zizyphus baclei = Z. mucronata (Hariot & Patouillard 1909) where it had been collected on fruits in March and November 1903 by Chevalier. In 1910, Magnus (1910) described Hyalodema evansii based on material collected by Pole Evans in 1906 at Zoutpansberg (Limpopo Province), South Africa, on Zizyphus sp., which was later also identified as Z. mucronata (Malençon 1953). Doidge (1950) cited the fungus under Coniodictyum evansii (Magnus) Höhn. without providing justification for this new combination. This is especially important because von Höhnel (1910, 1911) himself argued strongly for the conspecificity of C. chevalieri and H. evansii with C. chevalieri having priority, and therefore never made a new combination for this fungus. Thus, the only evident explanation for this inconsistency is that an error was inadvertently made with the epithet of Magnus' invalid description being mistakenly attached to the valid older genus name. Coniodictyum evansii (Doidge 1950) is, therefore, a synonymous nomen nudum for C. chevalieri.
The affinities of the fungus now known as C. chevalieri were first believed to be with the ascomycetes, and it was relegated to either the Hyphomycetes Mucedineae (Hariot & Patouillard 1909), the Melanconieae (von Höhnel 1911, Maublanc 1914) or the Mucedinaceae, Moniliales (Doidge 1950). However, already von Höhnel (1911) noted that some features of the hypertrophic growth resembled that of Exobasidium. When Malençon (1953) received abundant fresh material of the fungus collected by Th. Monod close to Dakar, Senegal, he performed an extensive morphological study concluding that the "conidiophores" producing the abundance of white spores were in reality basidia, and the spores hence basidiospores. He also, again, connected Coniodictyum systematically with gall-producing fungi described from Lauraceae of Central and South America in the genera Botryoconis and Clinoconidium as Maublanc had proposed before him, but then still under the ascomycetous Melanconieae (Maublanc 1914). Thus, after he had re-examined Botryoconis, Clinoconidium and Drepanoconis, Malençon named the family Cryptobasidieae (now Cryptobasidiaceae (Donk 1956) in honour of Alfred Lendner. This mycologist was the first to realise the basidiomycetous affinities of one of its members and had introduced the name Cryptobasidium (Lendner 1920), which was reduced to synonymy with Botryoconis. H. Sydow, like Maublanc, originally retained Botryoconis in the Melanconiaceae, but was convinced by Lendner's interpretations, concluding "Ich glaube nun, daß Clinoconidium und Botryoconis Basidiomyceten sind" and therefore transferred them accordingly (Sydow 1925). Only recently was Laurobasidium transferred from the Exobasidiaceae to the Cryptobasidiaceae (Begerow et al. 2002). Therefore, the Cryptobasidiaceae currently comprise five genera and seven species (compare Hendrichs et al. 2003).
The Cryptobasidiaceae have recently been confirmed to be monophyletic by Begerow et al. (2002), but the statistical support for the group in that study was low (obtaining a maximum of 59 % bootstrap). Our analyses, however, show that the family is highly supported both by bootstrap and Bayesian posterior probabilities. This result has obviously arisen from the larger taxon sampling within the Cryptobasidiaceae, while using the same gene region. This was especially possible, because additional sequences of Botryoconis and Laurobasidium had been deposited to GenBank by Nagao, Sato and Kakishima in 2004.
The only representative of the Cryptobasidiaceae in Africa, C. chevalieri, is also unique in its host preference and in its ecological occurrence in arid savanna biomes. This is markedly different to other members of the Cryptobasidiaceae that inhabit moist sub-tropical and tropical forests outside Africa attacking various genera in the laurel family while C. chevalieri so far has only been reported with certainty from Z. mucronata, a member of the Rhamnaceae. This unique biology, regarding its biogeography, ecology and host specificity, is reflected by the phylogenetic position of Coniodictyum, which is a sister taxon separated from the other members of the family that parasitize Lauraceae, by a long genetic distance and perfect support values (Fig. 7).
The potential of C. chevalieri to infect other members of the genus Zizyphus should be considered. The report in Doidge (1950) of C. chevalieri infecting Z. jujuba (Z. mauritiana?) is interesting in terms of the capacity of the pathogen to move to new hosts. However, the validity of the report could not be tested in this study and is regarded as rather doubtful. If the report were correct, it would have serious implications for countries like China and India where Z. mauritania and Z. jujuba are extensively grown for fruit production.
Malençon (1953) was convinced that Coniodictyum is a rare fungus ("en réalité est un champignon peu commun"). This is because he knew of no additional collections subsequent to the first collections from Chad and South Africa in 1903 and 1906, respectively, and the material that was sent to him from Senegal almost 50 years later. However, twelve collections made in South Africa over a considerable geographic range (compare above) and one in Zimbabwe between 1910 and 1938 documented in Doidge (1950) clearly escaped Malençon's notice. Thus, his statement regarding the rarity of the fungus is based on the incorrect assumption that the fungus had been collected only twice before he received the material from Dakar. Furthermore, the fungus was also collected in more recent years in KNP by Johannes van der Walt in 1974 and again in 1990 close to the camp-sites "Skukuza" and "Lower Sabie", respectively. It is however important to note that the fungus was almost absent from KNP in 2005, thus showing great fluctuations in its prevalence in different years. At this stage we speculate that the extensive spread of the fungus in 2004 was boosted by much higher rainfalls between January and April 2004, compared to the same months in 2005 (data not shown). Nevertheless, long-term observations are needed to either prove or disprove this hypothesis.
Another reason why C. chevalieri might not be as rare as previously believed, is provided by old galls found on branches of Z. mucronata. These indicate that the fungus had been present in Kruger Park in recent years. The frequency of collections of C. chevalieri, is, probably mainly determined by the number and activity of mycologists in areas of Africa, where Z. mucronata grows and we assume that it most likely could be found in the whole range of its host's distribution if extensively looked for. The situation appears to be similar in the representatives of Cryptobasidiaceae in tropical America where specimens have been recollected in Costa Rica in the late 1990s after a period of about 60 years absence of reports of these fungi (Gómez et al. 1998).
In 2004, many Z. mucronata trees were so heavily stressed by the production of large galls that we predicted large-scale death during the dry winter months. However, almost all infected trees remained alive in 2005 and appeared to have recovered well. This rapid recovery of Z. mucronata from the severe infection by C. chevalieri in 2004 is consistent with observations of rapid recovery and vigorous resprouting of Buffalo Thorn after fire damage. However, hardly any fruit could be found on the trees the year after they had been heavily infected at the two bushveld plots. We speculate that stress due to infection by C. chevalieri reduced plant vigour and consequently flower and fruit production in 2005. The fact that trees close to the dam had recovered well and produced abundant fruit, despite their being heavily infected in 2004, is probably due to favourable edaphic conditions at this site, with higher water availability, which reduced the impact of stress due to the disease.
This study represents the first report of an epidemic caused by C. chevalieri, a fungus previously believed to be extremely rare. Contrary to views regarding its rarity, we were able to show that C. chevalieri has been collected regularly, especially between 1906 and 1938, in various parts of South Africa. The infection status and the health of the trees in reference plots in KNP is being monitored and it is hoped that during coming years new knowledge concerning the ecology of the pathogen and the conditions favouring its spread will emerge. These will be potentially useful in developing hypotheses regarding modes of distribution and ecological factors that might have an effect on the survival and spread of the fungus.
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Acknowledgments |
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References |
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TOPAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
|---|
Akaike H (1974). A new look at the statistical model identification. IEEE Transactions on Automatic Control AC-19: 716–723.
Anderson JM (1999). Towards Gondwana alive. (Anderson JM, Berger L, de Wit M, Fatti LP, Holm E, Rubidge B, Smith G, Thackeray F, van Wyk B, eds). Gondwana Alive Society, Pretoria, South Africa.
Arndt SK, Clifford SC, Popp M (2001). Ziziphus - a multipurpose fruit tree for arid regions. In: Sustainable land use in deserts (Breckle S-W, Veste M, Wucherer W, eds.). Springer, Berlin, Germany:388 –399.
Arndt SK, Kayser O (2001). Ziziphus - Eine Heilpflanzengattung mit Tradition und Zukunft. Zeitschrift für Phytotherapie 22:98 –106.
Begerow D, Bauer R, Oberwinkler F (2002). The Exobasidiales: an evolutionary hypothesis. Mycological Progress 1:187 –199.[CrossRef]
Coates Palgrave K (2002). Trees of southern Africa. New edition revised and updated by Meg Coates Palgrave. Struik Publishers, Cape Town, South Africa.
Cunningham JL (1972). A miracle mounting fluid for permanent whole-mounts of microfungi. Mycologia 64:906 –911.[CrossRef]
Doidge EM (1950) The South African fungi and lichens to the end of 1945. Bothalia 5:1 –1094.
Donk MA (1956). The generic names proposed for Hymenomycetes - VI. Brachybasidiaceae, Cryptobasidiaceae, Exobasidiaceae. Reinwardtia 4:113 –118.
Gascuel O (1997). BIONJ: An improved version of the NJ algorithm based on a simple model of sequence data. Molecular Biology and Evolution 14:685 –695.[Abstract]
Gertenbach WPD (1980). Rainfall patterns in the Kruger National Park. Koedoe 23:35 –43.
Gertenbach WPD (1983). Landscapes of the Kruger National Park. Koedoe 26:9 –121.
Gómez, LD, Kisimova-Horowitz L (1998). Basidiomicetes de Costa Rica: nuevas especies de Exobasidium (Exobasidiaceae) y registros de Cryptobasidiales. Revista de Biología Tropical [online] 46: 1081–1093. ISSN 0034-7744.
Hariot MM, Patouillard N (1909). Coniodictyum, nouveau genre de Mucédinées. Bulletin Trimestriel de la Société Mycologique de France 25:13 –14.
Hendrichs M, Bauer R, Oberwinkler F (2003). The Cryptobasidiaceae of tropical Central and South America. Sydowia 55:33 –64.
Höhnel F von (1911). Mycologische Fragmente. Annales Mycologici 9:213 –216.
Huelsenbeck JP, Rannala B (2004). Frequentist properties of Bayesian posterior probabilities of phylogenetic trees under simple and complex substitution models. Systematic Biology 53:904 –913.[CrossRef][ISI][Medline]
Huelsenbeck JP, Ronquist F (2001). MRBAYES: Bayesian
inference of phylogenetic trees. Bioinformatics
17:754
–755.
Katoh K, Kuma K-I Toh H, Miyata T (2005). MAFFT
version 5: improvement in accuracy of multiple sequence alignment.
Nucleic Acids Research
33:511
–518.
Lendner A (1920). Un champignon parasite sur une Lauracée du genre Ocotea. Bulletin de la Société Botanique de Genève 2me série 12:122 –128.
Magnus P (1910). Ein neuer krebsartige Auswüchse an der Wirtspflanze veranlassender Pilz aus Transvaal. Berichte der Deutschen Botanischen Gesellschaft 28: 377–380, Tafel XI.
Malençon G (1953). Le Coniodyctium chevalieri Har. et Pat., sa nature et ses affinités. Bulletin Trimestriel de la Société Mycologique de France 69:77 –100.
Maublanc A (1914). Les genres Drepanonconis Schr. et Henn. et Clinoconidium Pat.: leur structure et leur place dans la classification. Bulletin Trimestriel de la Société Mycologique de France 30:441 –449.
Maurya SK, Devi S, Pandey VB, Khosa RL (1989). Content of betulin and betulinic acid, antitumor agents of Zizyphus species. Fitoterapia 60:468 –469.
Moncalvo J-M, Wang H-H, Hseu R-S (1995). Phylogenetic relationships in Ganoderma inferred from the internal transcribed spacers and 25S ribosomal DNA sequences. Mycologia 87:223 –238.[CrossRef][ISI]
Nunes PH, Marinho LC, Nunes ML, Soares EO (1987). Antipyretric activity of an aqueous extract of Zizyphus joazeiro Mart. (Rhamnaceae). Brazilian Journal of Medical Biological Research 20:599 –601.
Oberwinkler F (1977). Das neue System der Basidiomyceten. In: Beiträge zur Biologie der niederen Pflanzen (Frey H, Hurka H, Oberwinkler F, eds). G. Fischer, Stuttgart, Germany.
Pienaar U (1987). Field guide to the mammals of the Kruger National Park. Cape Town, South Africa.
Pinhey E (1972). Emperor Moths of south and south central Africa. C. Struik, Cape Town, South Africa.
Posada D, Crandall KA (1998). MODELTEST: testing the
model of DNA substitution. Bioinformatics
14:817
–818.
Ritz CM, Maier WFA, Oberwinkler F, Wissemann V (2005). Different evolutionary histories of two Phragmidium species infecting the same dog rose hosts. Mycological Research 109:603 –609.[CrossRef][Medline]
Ronquist F, Huelsenbeck JP (2003). MrBayes 3: Bayesian
phylogenetic inference under mixed models.
Bioinformatics 19:1572
–1574.
Rutherford MC (2003). Biomes of southern Africa: an objective categorization. 2nd edn., 1st reprint. National Botanical Institute, Pretoria, South Africa.
Swofford DL (2001) PAUP*. Phylogenetic analysis using parsimony (*and other methods). 4.0b10. Sinauer Associates, Sunderland, Massachussets, U.S.A.
Sydow H (1925). Fungi in itinere costaricensi collecti. Pars prima. Annales Mycologici 23:308 –429.
Tavaré S (1986). Some probabilistic and statistical problems on the analysis of DNA sequences. In: Lectures in mathematics in the life sciences. American Mathematical Society, U.S.A.: 57–86.
van der Walt JP, Yarrow D (1984) Methods for the isolation, maintenance, classification and identification of yeasts. In: The yeasts - a taxonomic study (Kreger-van Rij NJW, ed.) 3rd revised and enlarged edn. Elsevier, Amsterdam, The Netherlands:45 –104.
van Wyk P (1972). Trees of the Kruger National Park. Vol. I. Purnell, Cape Town, South Africa.
van Wyk P (1984). Field guide to the trees of the Kruger National Park. C. Struik Publishers, Cape Town, South Africa.
Vilgalys R, Hester M (1990). Rapid genetic
identification and mapping of enzymatically amplified ribosomal DNA from
several Cryptococcus species. Journal of
Bacteriology 172:4238
–4246.
Yang Z (1993). Maximum-likelihood estimation of phylogeny from DNA sequences when substitution rates differ over sites. Molecular Biology and Evolution 10:1396 –1401.[Abstract]
Yang Z (1994). Maximum likelihood phylogenetic
estimation from DNA sequences with variable rates over sites: Approximate
methods. Journal of Molecular Evolution
39:306
–314.[CrossRef][ISI][Medline]
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